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Next: Macros, Previous: Introduction to Function Definition, Up: Function Definition [Contents][Index]
To define a function in Maxima you use the := operator.
E.g.
f(x) := sin(x)
defines a function f.
Anonymous functions may also be created using lambda.
For example
lambda ([i, j], ...)
can be used instead of f
where
f(i,j) := block ([], ...); map (lambda ([i], i+1), l)
would return a list with 1 added to each term.
You may also define a function with a variable number of arguments, by having a final argument which is assigned to a list of the extra arguments:
(%i1) f ([u]) := u; (%o1) f([u]) := u (%i2) f (1, 2, 3, 4); (%o2) [1, 2, 3, 4] (%i3) f (a, b, [u]) := [a, b, u]; (%o3) f(a, b, [u]) := [a, b, u] (%i4) f (1, 2, 3, 4, 5, 6); (%o4) [1, 2, [3, 4, 5, 6]]
The right hand side of a function is an expression. Thus if you want a sequence of expressions, you do
f(x) := (expr1, expr2, ...., exprn);
and the value of exprn is what is returned by the function.
If you wish to make a return from some expression inside the
function then you must use block and return.
block ([], expr1, ..., if (a > 10) then return(a), ..., exprn)
is itself an expression, and so could take the place of the right hand side of a function definition. Here it may happen that the return happens earlier than the last expression.
The first [] in the block, may contain a list of variables and
variable assignments, such as [a: 3, b, c: []], which would cause the
three variables a,b,and c to not refer to their
global values, but rather have these special values for as long as the
code executes inside the block, or inside functions called from
inside the block. This is called dynamic binding, since the
variables last from the start of the block to the time it exits. Once
you return from the block, or throw out of it, the old values (if
any) of the variables will be restored. It is certainly a good idea
to protect your variables in this way. Note that the assignments
in the block variables, are done in parallel. This means, that if
you had used c: a in the above, the value of c would
have been the value of a at the time you just entered the block,
but before a was bound. Thus doing something like
block ([a: a], expr1, ... a: a+3, ..., exprn)
will protect the external value of a from being altered, but
would let you access what that value was. Thus the right hand
side of the assignments, is evaluated in the entering context, before
any binding occurs.
Using just block ([x], ...) would cause the x to have itself
as value, just as if it would have if you entered a fresh Maxima
session.
The actual arguments to a function are treated in exactly same way as the variables in a block. Thus in
f(x) := (expr1, ..., exprn);
and
f(1);
we would have a similar context for evaluation of the expressions as if we had done
block ([x: 1], expr1, ..., exprn)
Inside functions, when the right hand side of a definition,
may be computed at runtime, it is useful to use define and
possibly buildq.
A memoizing function caches the result the first time it is called with a given argument, and returns the stored value, without recomputing it, when that same argument is given. Memoizing functions are often called array function and are in fact handled like arrays in many ways:
The names of memoizing functions are appended to the global list arrays
(not the global list functions). arrayinfo returns the list of
arguments for which there are stored values, and listarray returns the
stored values. dispfun and fundef return the array function
definition.
arraymake constructs an array function call,
analogous to funmake for ordinary functions.
arrayapply applies an array function to its arguments,
analogous to apply for ordinary functions.
There is nothing exactly analogous to map for array functions,
although map(lambda([x], a[x]), L) or
makelist(a[x], x, L), where L is a list,
are not too far off the mark.
remarray removes an array function definition (including any stored
function values), analogous to remfunction for ordinary functions.
kill(a[x]) removes the value of the array function a
stored for the argument x;
the next time a is called with argument x,
the function value is recomputed.
However, there is no way to remove all of the stored values at once,
except for kill(a) or remarray(a),
which also remove the function definition.
Examples
If evaluating the function needs much time and only a limited number of points is ever evaluated (which means not much time is spent looking up results in a long list of cached results) Memoizing functions can speed up calculations considerably.
(%i1) showtime:true$ Evaluation took 0.0000 seconds (0.0000 elapsed) using 0 bytes.
(%i2) a[x]:=float(sum(sin(x*t),t,1,10000));
Evaluation took 0.0000 seconds (0.0000 elapsed) using 0 bytes.
(%o2) a := float(sum(sin(x t), t, 1, 10000))
x
(%i3) a[1]; Evaluation took 5.1250 seconds (5.1260 elapsed) using 775.250 MB. (%o3) 1.633891021792447
(%i4) a[1]; Evaluation took 0.0000 seconds (0.0000 elapsed) using 0 bytes. (%o4) 1.633891021792447
As the memoizing function is only evaluated once for each input value changes in variables the memoizing function uses are not considered for values that are already cached:
(%i1) a[x]:=b*x;
(%o1) a := b x
x
(%i2) b:1; (%o2) 1
(%i3) a[2]; (%o3) 2
(%i4) b:2; (%o4) 2
(%i5) a[1]; (%o5) 2
(%i6) a[2]; (%o6) 2
Next: Functions and Variables for Function Definition, Previous: Function, Up: Function Definition [Contents][Index]
Substitutes variables named by the list L into the expression expr,
in parallel, without evaluating expr. The resulting expression is
simplified, but not evaluated, after buildq carries out the substitution.
The elements of L are symbols or assignment expressions
symbol: value, evaluated in parallel. That is, the binding
of a variable on the right-hand side of an assignment is the binding of that
variable in the context from which buildq was called, not the binding of
that variable in the variable list L. If some variable in L is not
given an explicit assignment, its binding in buildq is the same as in
the context from which buildq was called.
Then the variables named by L are substituted into expr in parallel. That is, the substitution for every variable is determined before any substitution is made, so the substitution for one variable has no effect on any other.
If any variable x appears as splice (x) in expr,
then x must be bound to a list,
and the list is spliced (interpolated) into expr instead of substituted.
Any variables in expr not appearing in L are carried into the result
verbatim, even if they have bindings in the context from which buildq
was called.
Examples
a is explicitly bound to x, while b has the same binding
(namely 29) as in the calling context, and c is carried through verbatim.
The resulting expression is not evaluated until the explicit evaluation
''%.
(%i1) (a: 17, b: 29, c: 1729)$
(%i2) buildq ([a: x, b], a + b + c); (%o2) x + c + 29
(%i3) ''%; (%o3) x + 1758
e is bound to a list, which appears as such in the arguments of
foo, and interpolated into the arguments of bar.
(%i1) buildq ([e: [a, b, c]], foo (x, e, y)); (%o1) foo(x, [a, b, c], y)
(%i2) buildq ([e: [a, b, c]], bar (x, splice (e), y)); (%o2) bar(x, a, b, c, y)
The result is simplified after substitution. If simplification were applied before substitution, these two results would be the same.
(%i1) buildq ([e: [a, b, c]], splice (e) + splice (e)); (%o1) 2 c + 2 b + 2 a
(%i2) buildq ([e: [a, b, c]], 2 * splice (e)); (%o2) 2 a b c
The variables in L are bound in parallel; if bound sequentially,
the first result would be foo (b, b).
Substitutions are carried out in parallel;
compare the second result with the result of subst,
which carries out substitutions sequentially.
(%i1) buildq ([a: b, b: a], foo (a, b)); (%o1) foo(b, a)
(%i2) buildq ([u: v, v: w, w: x, x: y, y: z, z: u],
bar (u, v, w, x, y, z));
(%o2) bar(v, w, x, y, z, u)
(%i3) subst ([u=v, v=w, w=x, x=y, y=z, z=u],
bar (u, v, w, x, y, z));
(%o3) bar(u, u, u, u, u, u)
Construct a list of equations with some variables or expressions on the
left-hand side and their values on the right-hand side. macroexpand
shows the expression returned by show_values.
(%i1) show_values ([L]) ::= buildq ([L], map ("=", 'L, L));
(%o1) show_values([L]) ::= buildq([L], map("=", 'L, L))
(%i2) (a: 17, b: 29, c: 1729)$
(%i3) show_values (a, b, c - a - b); (%o3) [a = 17, b = 29, c - b - a = 1683]
(%i4) macroexpand (show_values (a, b, c - a - b)); (%o4) map(=, '([a, b, c - b - a]), [a, b, c - b - a])
Given a function of several arguments, create another function for which some of the arguments are fixed.
(%i1) curry (f, [a]) :=
buildq ([f, a], lambda ([[x]], apply (f, append (a, x))))$
(%i2) by3 : curry ("*", 3);
(%o2) lambda([[x]], apply(*, append([3], x)))
(%i3) by3 (a + b); (%o3) 3 (b + a)
Returns the macro expansion of expr without evaluating it,
when expr is a macro function call.
Otherwise, macroexpand returns expr.
If the expansion of expr yields another macro function call, that macro function call is also expanded.
macroexpand quotes its argument.
However, if the expansion of a macro function call has side effects,
those side effects are executed.
See also ::=, macros, and macroexpand1..
Examples
(%i1) g (x) ::= x / 99;
x
(%o1) g(x) ::= --
99
(%i2) h (x) ::= buildq ([x], g (x - a)); (%o2) h(x) ::= buildq([x], g(x - a))
(%i3) a: 1234; (%o3) 1234
(%i4) macroexpand (h (y));
y - a
(%o4) -----
99
(%i5) h (y);
y - 1234
(%o5) --------
99
Returns the macro expansion of expr without evaluating it,
when expr is a macro function call.
Otherwise, macroexpand1 returns expr.
macroexpand1 quotes its argument.
However, if the expansion of a macro function call has side effects,
those side effects are executed.
If the expansion of expr yields another macro function call, that macro function call is not expanded.
See also ::=, macros, and macroexpand.
Examples
(%i1) g (x) ::= x / 99;
x
(%o1) g(x) ::= --
99
(%i2) h (x) ::= buildq ([x], g (x - a)); (%o2) h(x) ::= buildq([x], g(x - a))
(%i3) a: 1234; (%o3) 1234
(%i4) macroexpand1 (h (y)); (%o4) g(y - a)
(%i5) h (y);
y - 1234
(%o5) --------
99
Default value: []
macros is the list of user-defined macro functions.
The macro function definition operator ::= puts a new macro function
onto this list, and kill, remove, and remfunction remove
macro functions from the list.
See also infolists.
Splices (interpolates) the list named by the atom a into an expression,
but only if splice appears within buildq;
otherwise, splice is treated as an undefined function.
If appearing within buildq as a alone (without splice),
a is substituted (not interpolated) as a list into the result.
The argument of splice can only be an atom;
it cannot be a literal list or an expression which yields a list.
Typically splice supplies the arguments for a function or operator.
For a function f, the expression f (splice (a)) within
buildq expands to f (a[1], a[2], a[3], ...).
For an operator o, the expression "o" (splice (a)) within
buildq expands to "o" (a[1], a[2], a[3], ...),
where o may be any type of operator (typically one which takes multiple
arguments). Note that the operator must be enclosed in double quotes ".
Examples
(%i1) buildq ([x: [1, %pi, z - y]], foo (splice (x)) / length (x));
foo(1, %pi, z - y)
(%o1) -----------------------
length([1, %pi, z - y])
(%i2) buildq ([x: [1, %pi]], "/" (splice (x)));
1
(%o2) ---
%pi
(%i3) matchfix ("<>", "<>");
(%o3) <>
(%i4) buildq ([x: [1, %pi, z - y]], "<>" (splice (x))); (%o4) <>1, %pi, z - y<>
Previous: Macros, Up: Function Definition [Contents][Index]
Constructs and evaluates an expression F(arg_1, ...,
arg_n).
apply does not attempt to distinguish a memoizing function from an ordinary
function; when F is the name of a memoizing function, apply evaluates
F(...) (that is, a function call with parentheses instead of square
brackets). arrayapply evaluates a function call with square brackets in
this case.
Examples:
apply evaluates its arguments.
In this example, min is applied to the value of L.
(%i1) L : [1, 5, -10.2, 4, 3]; (%o1) [1, 5, - 10.2, 4, 3]
(%i2) apply (min, L); (%o2) - 10.2
apply evaluates arguments, even if the function F quotes them.
(%i1) F (x) := x / 1729;
x
(%o1) F(x) := ----
1729
(%i2) fname : F; (%o2) F
(%i3) dispfun (F);
x
(%t3) F(x) := ----
1729
(%o3) [%t3]
(%i4) dispfun (fname); fundef: no such function: fname -- an error. To debug this try: debugmode(true);
(%i5) apply (dispfun, [fname]);
x
(%t5) F(x) := ----
1729
(%o5) [%t5]
apply evaluates the function name F.
Single quote ' defeats evaluation.
demoivre is the name of a global variable and also a function.
(%i1) demoivre; (%o1) false
(%i2) demoivre (exp (%i * x)); (%o2) %i sin(x) + cos(x)
(%i3) apply (demoivre, [exp (%i * x)]); apply: found false where a function was expected. -- an error. To debug this try: debugmode(true);
(%i4) apply ('demoivre, [exp (%i * x)]);
(%o4) %i sin(x) + cos(x)
How to convert a nested list into a matrix:
(%i1) a:[[1,2],[3,4]]; (%o1) [[1, 2], [3, 4]]
(%i2) apply(matrix,a);
[ 1 2 ]
(%o2) [ ]
[ 3 4 ]
The function block allows to make the variables v_1, …,
v_m to be local for a sequence of commands. If these variables
are already bound block saves the current values of the
variables v_1, …, v_m (if any) upon entry to the
block, then unbinds the variables so that they evaluate to themselves;
The local variables may be bound to arbitrary values within the block
but when the block is exited the saved values are restored, and the
values assigned within the block are lost.
If there is no need to define local variables then the list at the
beginning of the block command may be omitted.
In this case if neither return nor go are used
block behaves similar to the following construct:
( expr_1, expr_2,... , expr_n );
expr_1, …, expr_n will be evaluated in sequence and
the value of the last expression will be returned. The sequence can be
modified by the go, throw, and return functions. The last
expression is expr_n unless return or an expression containing
throw is evaluated.
The declaration local(v_1, ..., v_m) within block
saves the properties associated with the symbols v_1, …, v_m,
removes any properties before evaluating other expressions, and restores any
saved properties on exit from the block. Some declarations are implemented as
properties of a symbol, including :=, array, dependencies,
atvalue, matchdeclare, atomgrad, constant,
nonscalar, assume, and some others. The effect of local
is to make such declarations effective only within the block; otherwise
declarations within a block are actually global declarations.
block may appear within another block.
Local variables are established each time a new block is evaluated.
Local variables appear to be global to any enclosed blocks.
If a variable is non-local in a block,
its value is the value most recently assigned by an enclosing block, if any,
otherwise, it is the value of the variable in the global environment.
This policy may coincide with the usual understanding of "dynamic scope".
The value of the block is the value of the last statement or the
value of the argument to the function return which may be used to exit
explicitly from the block. The function go may be used to transfer
control to the statement of the block that is tagged with the argument
to go. To tag a statement, precede it by an atomic argument as
another statement in the block. For example:
block ([x], x:1, loop, x: x+1, ..., go(loop), ...). The argument to
go must be the name of a tag appearing within the block. One cannot use
go to transfer to a tag in a block other than the one containing the
go.
Blocks typically appear on the right side of a function definition but can be used in other places as well.
Evaluates and prints expr_1, …, expr_n and then
causes a Maxima break at which point the user can examine and change
his environment. Upon typing exit; the computation resumes.
Evaluates expr_1, …, expr_n one by one; if any
leads to the evaluation of an expression of the
form throw (arg), then the value of the catch is the value of
throw (arg), and no further expressions are evaluated.
This "non-local return" thus goes through any depth of
nesting to the nearest enclosing catch. If there is no catch
enclosing a throw, an error message is printed.
If the evaluation of the arguments does not lead to the evaluation of any
throw then the value of catch is the value of expr_n.
(%i1) lambda ([x], if x < 0 then throw(x) else f(x))$
(%i2) g(l) := catch (map (''%, l))$
(%i3) g ([1, 2, 3, 7]);
(%o3) [f(1), f(2), f(3), f(7)]
(%i4) g ([1, 2, -3, 7]);
(%o4) - 3
The function g returns a list of f of each element of l if
l consists only of non-negative numbers; otherwise, g "catches"
the first negative element of l and "throws" it up.
Translates Maxima functions into Lisp and writes the translated code into the file filename.
compfile(filename, f_1, ..., f_n) translates the
specified functions. compfile (filename, functions) and
compfile (filename, all) translate all user-defined functions.
The Lisp translations are not evaluated, nor is the output file processed by
the Lisp compiler.
translate creates and evaluates Lisp translations. compile_file
translates Maxima into Lisp, and then executes the Lisp compiler.
See also translate, translate_file, and compile_file.
Translates Maxima functions f_1, …, f_n into Lisp, evaluates
the Lisp translations, and calls the Lisp function COMPILE on each
translated function. compile returns a list of the names of the
compiled functions.
compile (all) or compile (functions) compiles all user-defined
functions.
compile quotes its arguments;
the quote-quote operator '' defeats quotation.
Compiling a function to native code can mean a big increase in speed and might cause the memory footprint to reduce drastically. Code tends to be especially effective when the flexibility it needs to provide is limited. If compilation doesn’t provide the speed that is needed a few ways to limit the code’s functionality are the following:
mode_declare or a statement like the following one:
put(x_1, bigfloat, numerical_type)
'
tells the compiler that the text is meant as an option.
Defines a function named f with arguments x_1, …, x_n
and function body expr. define always evaluates its second
argument (unless explicitly quoted). The function so defined may be an ordinary
Maxima function (with arguments enclosed in parentheses) or a memoizing function
(with arguments enclosed in square brackets).
When the last or only function argument x_n is a list of one element,
the function defined by define accepts a variable number of arguments.
Actual arguments are assigned one-to-one to formal arguments x_1, …,
x_(n - 1), and any further actual arguments, if present, are assigned to
x_n as a list.
When the first argument of define is an expression of the form
f(x_1, ..., x_n) or f[x_1, ...,
x_n], the function arguments are evaluated but f is not evaluated,
even if there is already a function or variable by that name.
When the first argument is an expression with operator funmake,
arraymake, or ev, the first argument is evaluated;
this allows for the function name to be computed, as well as the body.
All function definitions appear in the same namespace; defining a function
f within another function g does not automatically limit the scope
of f to g. However, local(f) makes the definition of
function f effective only within the block or other compound expression
in which local appears.
If some formal argument x_k is a quoted symbol (after evaluation), the
function defined by define does not evaluate the corresponding actual
argument. Otherwise all actual arguments are evaluated.
Examples:
define always evaluates its second argument (unless explicitly quoted).
(%i1) expr : cos(y) - sin(x); (%o1) cos(y) - sin(x)
(%i2) define (F1 (x, y), expr); (%o2) F1(x, y) := cos(y) - sin(x)
(%i3) F1 (a, b); (%o3) cos(b) - sin(a)
(%i4) F2 (x, y) := expr; (%o4) F2(x, y) := expr
(%i5) F2 (a, b); (%o5) cos(y) - sin(x)
The function defined by define may be an ordinary Maxima function or a
memoizing function.
(%i1) define (G1 (x, y), x.y - y.x); (%o1) G1(x, y) := x . y - y . x
(%i2) define (G2 [x, y], x.y - y.x);
(%o2) G2 := x . y - y . x
x, y
When the last or only function argument x_n is a list of one element,
the function defined by define accepts a variable number of arguments.
(%i1) define (H ([L]), '(apply ("+", L)));
(%o1) H([L]) := apply("+", L)
(%i2) H (a, b, c); (%o2) c + b + a
When the first argument is an expression with operator funmake,
arraymake, or ev, the first argument is evaluated.
(%i1) [F : I, u : x]; (%o1) [I, x]
(%i2) funmake (F, [u]); (%o2) I(x)
(%i3) define (funmake (F, [u]), cos(u) + 1); (%o3) I(x) := cos(x) + 1
(%i4) define (arraymake (F, [u]), cos(u) + 1);
(%o4) I := cos(x) + 1
x
(%i5) define (foo (x, y), bar (y, x)); (%o5) foo(x, y) := bar(y, x)
(%i6) define (ev (foo (x, y)), sin(x) - cos(y)); (%o6) bar(y, x) := sin(x) - cos(y)
Introduces a global variable into the Maxima environment.
define_variable is useful in user-written packages, which are often
translated or compiled as it gives the compiler hints of the type (“mode”)
of a variable and therefore avoids requiring it to generate generic code that
can deal with every variable being an integer, float, maxima object, array etc.
define_variable carries out the following steps:
mode_declare (name, mode) declares the mode (“type”) of
name to the translator which can considerably speed up compiled code as
it allows having to create generic code. See mode_declare for a list of
the possible modes.
The value_check property can be assigned to any variable which has been
defined via define_variable with a mode other than any.
The value_check property is a lambda expression or the name of a function
of one variable, which is called when an attempt is made to assign a value to
the variable. The argument of the value_check function is the would-be
assigned value.
define_variable evaluates default_value, and quotes name
and mode. define_variable returns the current value of
name, which is default_value if name was unbound before,
and otherwise it is the previous value of name.
Examples:
foo is a Boolean variable, with the initial value true.
(%i1) define_variable (foo, true, boolean); (%o1) true
(%i2) foo; (%o2) true
(%i3) foo: false; (%o3) false
(%i4) foo: %pi;
translator: foo was declared with mode boolean
, but it has value: %pi
-- an error. To debug this try: debugmode(true);
(%i5) foo; (%o5) false
bar is an integer variable, which must be prime.
(%i1) define_variable (bar, 2, integer); (%o1) 2
(%i2) qput (bar, prime_test, value_check); (%o2) prime_test
(%i3) prime_test (y) := if not primep(y) then
error (y, "is not prime.");
(%o3) prime_test(y) := if not primep(y)
then error(y, "is not prime.")
(%i4) bar: 1439; (%o4) 1439
(%i5) bar: 1440; 1440 is not prime. #0: prime_test(y=1440) -- an error. To debug this try: debugmode(true);
(%i6) bar; (%o6) 1439
baz_quux is a variable which cannot be assigned a value.
The mode any_check is like any, but any_check enables the
value_check mechanism, and any does not.
(%i1) define_variable (baz_quux, 'baz_quux, any_check); (%o1) baz_quux
(%i2) F: lambda ([y], if y # 'baz_quux then
error ("Cannot assign to `baz_quux'."));
(%o2) lambda([y], if y # 'baz_quux
then error(Cannot assign to `baz_quux'.))
(%i3) qput (baz_quux, ''F, value_check);
(%o3) lambda([y], if y # 'baz_quux
then error(Cannot assign to `baz_quux'.))
(%i4) baz_quux: 'baz_quux; (%o4) baz_quux
(%i5) baz_quux: sqrt(2);
Cannot assign to `baz_quux'.
#0: lambda([y],if y # 'baz_quux then
error("Cannot assign to `baz_quux'."))(y=sqrt(2))
-- an error. To debug this try: debugmode(true);
(%i6) baz_quux; (%o6) baz_quux
Displays the definition of the user-defined functions f_1, …,
f_n. Each argument may be the name of a macro (defined with ::=),
an ordinary function (defined with := or define), an array
function (defined with := or define, but enclosing arguments in
square brackets [ ]), a subscripted function (defined with := or
define, but enclosing some arguments in square brackets and others in
parentheses ( )), one of a family of subscripted functions selected by a
particular subscript value, or a subscripted function defined with a constant
subscript.
dispfun (all) displays all user-defined functions as
given by the functions, arrays, and macros lists,
omitting subscripted functions defined with constant subscripts.
dispfun creates an intermediate expression label
(%t1, %t2, etc.)
for each displayed function, and assigns the function definition to the label.
In contrast, fundef returns the function definition.
dispfun quotes its arguments; the quote-quote operator ''
defeats quotation. dispfun returns the list of intermediate expression
labels corresponding to the displayed functions.
Examples:
(%i1) m(x, y) ::= x^(-y);
- y
(%o1) m(x, y) ::= x
(%i2) f(x, y) := x^(-y);
- y
(%o2) f(x, y) := x
(%i3) g[x, y] := x^(-y);
- y
(%o3) g := x
x, y
(%i4) h[x](y) := x^(-y);
- y
(%o4) h (y) := x
x
(%i5) i[8](y) := 8^(-y);
- y
(%o5) i (y) := 8
8
(%i6) dispfun (m, f, g, h, h[5], h[10], i[8]);
- y
(%t6) m(x, y) ::= x
- y
(%t7) f(x, y) := x
- y
(%t8) g := x
x, y
- y
(%t9) h (y) := x
x
1
(%t10) h (y) := --
5 y
5
1
(%t11) h (y) := ---
10 y
10
- y
(%t12) i (y) := 8
8
(%o12) [%t6, %t7, %t8, %t9, %t10, %t11, %t12]
(%i13) ''%;
- y - y - y
(%o13) [m(x, y) ::= x , f(x, y) := x , g := x ,
x, y
- y 1 1 - y
h (y) := x , h (y) := --, h (y) := ---, i (y) := 8 ]
x 5 y 10 y 8
5 10
Similar to map, but fullmap keeps mapping down all subexpressions
until the main operators are no longer the same.
fullmap is used by the Maxima simplifier for certain matrix
manipulations; thus, Maxima sometimes generates an error message concerning
fullmap even though fullmap was not explicitly called by the user.
Examples:
(%i1) a + b * c; (%o1) b c + a
(%i2) fullmap (g, %); (%o2) g(b) g(c) + g(a)
(%i3) map (g, %th(2)); (%o3) g(b c) + g(a)
Similar to fullmap, but fullmapl only maps onto lists and
matrices.
Example:
(%i1) fullmapl ("+", [3, [4, 5]], [[a, 1], [0, -1.5]]);
(%o1) [[a + 3, 4], [4, 3.5]]
Default value: []
functions is the list of ordinary Maxima functions
in the current session.
An ordinary function is a function constructed by
define or := and called with parentheses ().
A function may be defined at the Maxima prompt
or in a Maxima file loaded by load or batch.
Memoizing functions (called with square brackets, e.g., F[x]) and subscripted
functions (called with square brackets and parentheses, e.g., F[x](y))
are listed by the global variable arrays, and not by functions.
Lisp functions are not kept on any list.
Examples:
(%i1) F_1 (x) := x - 100; (%o1) F_1(x) := x - 100
(%i2) F_2 (x, y) := x / y;
x
(%o2) F_2(x, y) := -
y
(%i3) define (F_3 (x), sqrt (x)); (%o3) F_3(x) := sqrt(x)
(%i4) G_1 [x] := x - 100;
(%o4) G_1 := x - 100
x
(%i5) G_2 [x, y] := x / y;
x
(%o5) G_2 := -
x, y y
(%i6) define (G_3 [x], sqrt (x));
(%o6) G_3 := sqrt(x)
x
(%i7) H_1 [x] (y) := x^y;
y
(%o7) H_1 (y) := x
x
(%i8) functions; (%o8) [F_1(x), F_2(x, y), F_3(x)]
(%i9) arrays; (%o9) [G_1, G_2, G_3, H_1]
Returns the definition of the function f.
The argument may be
::=),
:= or define),
memoizing function (defined with := or define, but enclosing arguments in square brackets [ ]),
:= or define,
but enclosing some arguments in square brackets and others in parentheses
( )),
fundef quotes its argument;
the quote-quote operator '' defeats quotation.
fundef (f) returns the definition of f.
In contrast, dispfun (f) creates an intermediate expression label
and assigns the definition to the label.
Returns an expression F(arg_1, ..., arg_n).
The return value is simplified, but not evaluated,
so the function F is not called, even if it exists.
funmake does not attempt to distinguish memoizing functions from ordinary
functions; when F is the name of a memoizing function,
funmake returns F(...)
(that is, a function call with parentheses instead of square brackets).
arraymake returns a function call with square brackets in this case.
funmake evaluates its arguments.
Examples:
funmake applied to an ordinary Maxima function.
(%i1) F (x, y) := y^2 - x^2;
2 2
(%o1) F(x, y) := y - x
(%i2) funmake (F, [a + 1, b + 1]); (%o2) F(a + 1, b + 1)
(%i3) ''%;
2 2
(%o3) (b + 1) - (a + 1)
funmake applied to a macro.
(%i1) G (x) ::= (x - 1)/2;
x - 1
(%o1) G(x) ::= -----
2
(%i2) funmake (G, [u]); (%o2) G(u)
(%i3) ''%;
u - 1
(%o3) -----
2
funmake applied to a subscripted function.
(%i1) H [a] (x) := (x - 1)^a;
a
(%o1) H (x) := (x - 1)
a
(%i2) funmake (H [n], [%e]);
n
(%o2) lambda([x], (x - 1) )(%e)
(%i3) ''%;
n
(%o3) (%e - 1)
(%i4) funmake ('(H [n]), [%e]);
(%o4) H (%e)
n
(%i5) ''%;
n
(%o5) (%e - 1)
funmake applied to a symbol which is not a defined function of any kind.
(%i1) funmake (A, [u]); (%o1) A(u)
(%i2) ''%; (%o2) A(u)
funmake evaluates its arguments, but not the return value.
(%i1) det(a,b,c) := b^2 -4*a*c;
2
(%o1) det(a, b, c) := b - 4 a c
(%i2) (x : 8, y : 10, z : 12); (%o2) 12
(%i3) f : det; (%o3) det
(%i4) funmake (f, [x, y, z]); (%o4) det(8, 10, 12)
(%i5) ''%; (%o5) - 284
Maxima simplifies funmake’s return value.
(%i1) funmake (sin, [%pi / 2]); (%o1) 1
Defines and returns a lambda expression (that is, an anonymous function). The function may have required arguments x_1, …, x_m and/or optional arguments L, which appear within the function body as a list. The return value of the function is expr_n. A lambda expression can be assigned to a variable and evaluated like an ordinary function. A lambda expression may appear in some contexts in which a function name is expected.
When the function is evaluated, unbound local variables x_1, …,
x_m are created. lambda may appear within block or another
lambda; local variables are established each time another block or
lambda is evaluated. Local variables appear to be global to any enclosed
block or lambda. If a variable is not local, its value is the
value most recently assigned in an enclosing block or lambda, if
any, otherwise, it is the value of the variable in the global environment.
This policy may coincide with the usual understanding of "dynamic scope".
After local variables are established, expr_1 through expr_n are
evaluated in turn. The special variable %%, representing the value of
the preceding expression, is recognized. throw and catch may also
appear in the list of expressions.
return cannot appear in a lambda expression unless enclosed by
block, in which case return defines the return value of the block
and not of the lambda expression, unless the block happens to be expr_n.
Likewise, go cannot appear in a lambda expression unless enclosed by
block.
lambda quotes its arguments;
the quote-quote operator '' defeats quotation.
Examples:
(%i1) f: lambda ([x], x^2);
2
(%o1) lambda([x], x )
(%i2) f(a);
2
(%o2) a
(%i1) lambda ([x], x^2) (a);
2
(%o1) a
(%i2) apply (lambda ([x], x^2), [a]);
2
(%o2) a
(%i3) map (lambda ([x], x^2), [a, b, c, d, e]);
2 2 2 2 2
(%o3) [a , b , c , d , e ]
''.
(%i1) a: %pi$ (%i2) b: %e$
(%i3) g: lambda ([a], a*b); (%o3) lambda([a], a b)
(%i4) b: %gamma$
(%i5) g(1/2);
%gamma
(%o5) ------
2
(%i6) g2: lambda ([a], a*''b); (%o6) lambda([a], a %gamma)
(%i7) b: %e$
(%i8) g2(1/2);
%gamma
(%o8) ------
2
(%i1) h: lambda ([a, b], h2: lambda ([a], a*b), h2(1/2));
1
(%o1) lambda([a, b], h2 : lambda([a], a b), h2(-))
2
(%i2) h(%pi, %gamma);
%gamma
(%o2) ------
2
lambda quotes its arguments, lambda expression i below does
not define a "multiply by a" function. Such a function can be defined
via buildq, as in lambda expression i2 below.
(%i1) i: lambda ([a], lambda ([x], a*x)); (%o1) lambda([a], lambda([x], a x))
(%i2) i(1/2); (%o2) lambda([x], a x)
(%i3) i2: lambda([a], buildq([a: a], lambda([x], a*x))); (%o3) lambda([a], buildq([a : a], lambda([x], a x)))
(%i4) i2(1/2);
1
(%o4) lambda([x], (-) x)
2
(%i5) i2(1/2)(%pi);
%pi
(%o5) ---
2
[L] as the sole or final argument.
The arguments appear within the function body as a list.
(%i1) f : lambda ([aa, bb, [cc]], aa * cc + bb); (%o1) lambda([aa, bb, [cc]], aa cc + bb)
(%i2) f (foo, %i, 17, 29, 256); (%o2) [17 foo + %i, 29 foo + %i, 256 foo + %i]
(%i3) g : lambda ([[aa]], apply ("+", aa));
(%o3) lambda([[aa]], apply(+, aa))
(%i4) g (17, 29, x, y, z, %e); (%o4) z + y + x + %e + 46
Saves the properties associated with the symbols v_1, …, v_n,
removes any properties before evaluating other expressions,
and restores any saved properties on exit
from the block or other compound expression in which local appears.
Some declarations are implemented as properties of a symbol, including
:=, array, dependencies, atvalue,
matchdeclare, atomgrad, constant, nonscalar,
assume, and some others. The effect of local is to make such
declarations effective only within the block or other compound expression in
which local appears; otherwise such declarations are global declarations.
local can only appear in block
or in the body of a function definition or lambda expression,
and only one occurrence is permitted in each.
local quotes its arguments.
local returns done.
Example:
A local function definition.
(%i1) foo (x) := 1 - x; (%o1) foo(x) := 1 - x
(%i2) foo (100); (%o2) - 99
(%i3) block (local (foo), foo (x) := 2 * x, foo (100)); (%o3) 200
(%i4) foo (100); (%o4) - 99
Default value: false
macroexpansion controls whether the expansion (that is, the return value)
of a macro function is substituted for the macro function call.
A substitution may speed up subsequent expression evaluations,
at the cost of storing the expansion.
falseThe expansion of a macro function is not substituted for the macro function call.
expandThe first time a macro function call is evaluated,
the expansion is stored.
The expansion is not recomputed on subsequent calls;
any side effects (such as print or assignment to global variables) happen
only when the macro function call is first evaluated.
Expansion in an expression does not affect other expressions
which have the same macro function call.
displaceThe first time a macro function call is evaluated, the expansion is substituted for the call, thus modifying the expression from which the macro function was called. The expansion is not recomputed on subsequent calls; any side effects happen only when the macro function call is first evaluated. Expansion in an expression does not affect other expressions which have the same macro function call.
Examples
When macroexpansion is false,
a macro function is called every time the calling expression is evaluated,
and the calling expression is not modified.
(%i1) f (x) := h (x) / g (x);
h(x)
(%o1) f(x) := ----
g(x)
(%i2) g (x) ::= block (print ("x + 99 is equal to", x),
return (x + 99));
(%o2) g(x) ::= block(print("x + 99 is equal to", x),
return(x + 99))
(%i3) h (x) ::= block (print ("x - 99 is equal to", x),
return (x - 99));
(%o3) h(x) ::= block(print("x - 99 is equal to", x),
return(x - 99))
(%i4) macroexpansion: false; (%o4) false
(%i5) f (a * b);
x - 99 is equal to x
x + 99 is equal to x
a b - 99
(%o5) --------
a b + 99
(%i6) dispfun (f);
h(x)
(%t6) f(x) := ----
g(x)
(%o6) [%t6]
(%i7) f (a * b);
x - 99 is equal to x
x + 99 is equal to x
a b - 99
(%o7) --------
a b + 99
When macroexpansion is expand,
a macro function is called once,
and the calling expression is not modified.
(%i1) f (x) := h (x) / g (x);
h(x)
(%o1) f(x) := ----
g(x)
(%i2) g (x) ::= block (print ("x + 99 is equal to", x),
return (x + 99));
(%o2) g(x) ::= block(print("x + 99 is equal to", x),
return(x + 99))
(%i3) h (x) ::= block (print ("x - 99 is equal to", x),
return (x - 99));
(%o3) h(x) ::= block(print("x - 99 is equal to", x),
return(x - 99))
(%i4) macroexpansion: expand; (%o4) expand
(%i5) f (a * b);
x - 99 is equal to x
x + 99 is equal to x
a b - 99
(%o5) --------
a b + 99
(%i6) dispfun (f);
mmacroexpanded(x - 99, h(x))
(%t6) f(x) := ----------------------------
mmacroexpanded(x + 99, g(x))
(%o6) [%t6]
(%i7) f (a * b);
a b - 99
(%o7) --------
a b + 99
When macroexpansion is displace,
a macro function is called once,
and the calling expression is modified.
(%i1) f (x) := h (x) / g (x);
h(x)
(%o1) f(x) := ----
g(x)
(%i2) g (x) ::= block (print ("x + 99 is equal to", x),
return (x + 99));
(%o2) g(x) ::= block(print("x + 99 is equal to", x),
return(x + 99))
(%i3) h (x) ::= block (print ("x - 99 is equal to", x),
return (x - 99));
(%o3) h(x) ::= block(print("x - 99 is equal to", x),
return(x - 99))
(%i4) macroexpansion: displace; (%o4) displace
(%i5) f (a * b);
x - 99 is equal to x
x + 99 is equal to x
a b - 99
(%o5) --------
a b + 99
(%i6) dispfun (f);
x - 99
(%t6) f(x) := ------
x + 99
(%o6) [%t6]
(%i7) f (a * b);
a b - 99
(%o7) --------
a b + 99
A mode_declare informs the compiler which type (lisp programmers name the type:
“mode”) a function parameter or its return value will be of. This can greatly
boost the efficiency of the code the compiler generates: Without knowing the type of
all variables and knowing the return value of all functions a function uses
in advance very generic (and thus potentially slow) code needs to be generated.
The arguments of mode_declare are pairs consisting of a variable (or a list
of variables all having the same mode) and a mode. Available modes (“types”) are:
array an declared array (see the detailed description below) boolean true or false integer integers (including arbitrary-size integers) fixnum integers (excluding arbitrary-size integers) float machine-size floating-point numbers real machine-size floating-point or integer number Numbers any any kind of object (useful for arrays of any)
A function parameter named a can be declared as an array filled with elements
of the type t the following way:
mode_declare (a, array(t, dim1, dim2, ...))
If none of the elements of the array a needs to be checked if it still doesn’t
contain a value additional code can be omitted by declaring this fact, too:
mode_declare (a, array (t, complete, dim1, dim2, ...))
The complete has no effect if all array elements are of the type
fixnum or float: Machine-sized numbers inevitably contain a value
(and will automatically be initialized to 0 in most lisp implementations).
Another way to tell that all entries of the array a are of the type
(“mode”) m and have been assigned a value to would be:
mode_declare (completearray (a), m))
Numeric code using arrays might run faster still if the size of the array is known at compile time, as well, as in:
mode_declare (completearray (a [10, 10]), float)
for a floating point number array named a which is 10 x 10.
mode_declare also can be used in order to declare the type of the result
of a function. In this case the function compilation needs to be preceded by
another mode_declare statement. For example the expression,
mode_declare ([function (f_1, f_2, ...)], fixnum)
declares that the values returned by f_1, f_2, … are
single-word integers.
modedeclare is a synonym for mode_declare.
If the type of function parameters and results doesn’t match the declaration by
mode_declare the function may misbehave or a warning or an error might
occur, see mode_checkp, mode_check_errorp and
mode_check_warnp.
See mode_identity for declaring the type of lists and define_variable for
declaring the type of all global variables compiled code uses, as well.
Example:
(%i1) square_float(f):=(
mode_declare(f,float),
f*f
);
(%o1) square_float(f) := (mode_declare(f, float), f f)
(%i2) mode_declare([function(f)],float); (%o2) [[function(f)]]
(%i3) compile(square_float); (%o3) [square_float]
(%i4) square_float(100.0); (%o4) 10000.0
Default value: true
When mode_checkp is true, mode_declare does not only define
which type a variable will be of so the compiler can generate more efficient code,
but will also create a runtime warning if the variable isn’t of the variable type
the code was compiled to deal with.
(%i1) mode_checkp:true; (%o1) true
(%i2) square(f):=(
mode_declare(f,float),
f^2);
2
(%o2) square(f) := (mode_declare(f, float), f )
(%i3) compile(square); (%o3) [square]
(%i4) square(2.3); (%o4) 5.289999999999999
(%i5) square(4); Maxima encountered a Lisp error: The value 4 is not of type DOUBLE-FLOAT when binding $F Automatically continuing. To enable the Lisp debugger set *debugger-hook* to nil.
Default value: false
When mode_check_errorp is true, mode_declare calls
error.
Default value: true
When mode_check_warnp is true, mode errors are
described.
mode_identity works similar to mode_declare, but is used for
informing the compiler that a thing like a macro or a list operation
will only return a specific type of object. The purpose of doing so is that
maxima supports many objects: Machine integers, arbitrary length integers,
equations, machine floats, big floats, which means that for everything that
deals with return values of operations that can result in any object the
compiler needs to output generic (and therefore potentially slow) code.
The first argument to mode_identity is the type of return value
something will return (for possible types see mode_declare).
(i.e., one of float, fixnum, number,
The second argument is the expression that will return an object of this
type.
If the the return value of this expression is of a type the code was not compiled for error or warning is signalled.
If you knew that first (l) returned a number then you could write
mode_identity (number, first (l)).
However, if you need this construct more often it would be more efficient to define a function that returns a number fist:
firstnumb (x) ::= buildq ([x], mode_identity (number, first(x))); compile(firstnumb)
firstnumb now can be used every time you need the first element
of a list that is guaranteed to be filled with numbers.
Unbinds the function definitions of the symbols f_1, …, f_n.
The arguments may be the names of ordinary functions (created by := or
define) or macro functions (created by ::=).
remfunction (all) unbinds all function definitions.
remfunction quotes its arguments.
remfunction returns a list of the symbols for which the function
definition was unbound. false is returned in place of any symbol for
which there is no function definition.
remfunction does not apply to memoizing functions or subscripted functions.
remarray applies to those types of functions.
Default value: true
When savedef is true, the Maxima version of a user function is
preserved when the function is translated. This permits the definition to be
displayed by dispfun and allows the function to be edited.
When savedef is false, the names of translated functions are
removed from the functions list.
Translates the user-defined functions f_1, …, f_n from the Maxima language into Lisp and evaluates the Lisp translations. Typically the translated functions run faster than the originals.
translate (all) or translate (functions) translates all
user-defined functions.
Functions to be translated should include a call to mode_declare at the
beginning when possible in order to produce more efficient code. For example:
f (x_1, x_2, ...) := block ([v_1, v_2, ...],
mode_declare (v_1, mode_1, v_2, mode_2, ...), ...)
where the x_1, x_2, … are the parameters to the function and the v_1, v_2, … are the local variables.
The names of translated functions are removed from the functions list
if savedef is false (see below) and are added to the props
lists.
Functions should not be translated unless they are fully debugged.
Expressions are assumed simplified; if they are not, correct but non-optimal
code gets generated. Thus, the user should not set the simp switch to
false which inhibits simplification of the expressions to be translated.
The switch translate, if true, causes automatic
translation of a user’s function to Lisp.
Note that translated
functions may not run identically to the way they did before
translation as certain incompatibilities may exist between the Lisp
and Maxima versions. Principally, the rat function with more than
one argument and the ratvars function should not be used if any
variables are mode_declare’d canonical rational expressions (CRE).
Also the prederror: false setting
will not translate.
savedef - if true will cause the Maxima version of a user
function to remain when the function is translate’d. This permits the
definition to be displayed by dispfun and allows the function to be
edited.
transrun - if false will cause the interpreted version of all
functions to be run (provided they are still around) rather than the
translated version.
The result returned by translate is a list of the names of the
functions translated.
Translates a file of Maxima code into a file of Lisp code.
translate_file returns a list of three filenames:
the name of the Maxima file, the name of the Lisp file, and the name of file
containing additional information about the translation.
translate_file evaluates its arguments.
translate_file ("foo.mac"); load("foo.LISP") is the same as the command
batch ("foo.mac") except for certain restrictions, the use of
'' and %, for example.
translate_file (maxima_filename) translates a Maxima file
maxima_filename into a similarly-named Lisp file.
For example, foo.mac is translated into foo.LISP.
The Maxima filename may include a directory name or names,
in which case the Lisp output file is written
to the same directory from which the Maxima input comes.
translate_file (maxima_filename, lisp_filename) translates
a Maxima file maxima_filename into a Lisp file lisp_filename.
translate_file ignores the filename extension, if any, of
lisp_filename; the filename extension of the Lisp output file is always
LISP. The Lisp filename may include a directory name or names,
in which case the Lisp output file is written to the specified directory.
translate_file also writes a file of translator warning
messages of various degrees of severity.
The filename extension of this file is UNLISP.
This file may contain valuable information, though possibly obscure,
for tracking down bugs in translated code.
The UNLISP file is always written
to the same directory from which the Maxima input comes.
translate_file emits Lisp code which causes
some declarations and definitions to take effect as soon
as the Lisp code is compiled.
See compile_file for more on this topic.
See also
tr_array_as_ref
tr_bound_function_applyp,
tr_exponent
tr_file_tty_messagesp,
tr_float_can_branch_complex,
tr_function_call_default,
tr_numer,
tr_optimize_max_loop,
tr_state_vars,
tr_warnings_get,
tr_warn_bad_function_calls
tr_warn_fexpr,
tr_warn_meval,
tr_warn_mode,
tr_warn_undeclared,
and tr_warn_undefined_variable.
Default value: true
When transrun is false will cause the interpreted
version of all functions to be run (provided they are still around)
rather than the translated version.
Default value: true
If translate_fast_arrays is false, array references in Lisp code
emitted by translate_file are affected by tr_array_as_ref.
When tr_array_as_ref is true,
array names are evaluated,
otherwise array names appear as literal symbols in translated code.
tr_array_as_ref has no effect if translate_fast_arrays is
true.
Default value: true
When tr_bound_function_applyp is true and tr_function_call_default
is general, if a bound variable (such as a function argument) is found being
used as a function then Maxima will rewrite that function call using apply and
print a warning message.
For example, if g is defined by g(f,x) := f(x+1) then translating
g will cause Maxima to print a warning and rewrite f(x+1) as
apply(f,[x+1]).
(%i1) f (x) := x^2$ (%i2) g (f) := f (3)$ (%i3) tr_bound_function_applyp : true$
(%i4) translate (g)$ warning: f is a bound variable in f(3), but it is used as a function. note: instead I'll translate it as: apply(f,[3])
(%i5) g (lambda ([x], x)); (%o5) 3
(%i6) tr_bound_function_applyp : false$ (%i7) translate (g)$
(%i8) g (lambda ([x], x)); (%o8) 9
Default value: false
When tr_file_tty_messagesp is true, messages generated by
translate_file during translation of a file are displayed on the console
and inserted into the UNLISP file. When false, messages about
translation of the file are only inserted into the UNLISP file.
Default value: true
Tells the Maxima-to-Lisp translator to assume that the functions
acos, asin, asec, acsc, acosh,
asech, atanh, acoth, log and sqrt
can return complex results.
When it is true then acos(x) is of mode any
even if x is of mode float (as set by mode_declare).
When false then acos(x) is of mode
float if and only if x is of mode float.
Default value: general
false means give up and call meval, expr means assume Lisp
fixed arg function. general, the default gives code good for
mexprs and mlexprs but not macros. general assures
variable bindings are correct in compiled code. In general mode, when
translating F(X), if F is a bound variable, then it assumes that
apply (f, [x]) is meant, and translates a such, with appropriate warning.
There is no need to turn this off. With the default settings, no warning
messages implies full compatibility of translated and compiled code with the
Maxima interpreter.
Default value: false
When tr_numer is true, numer properties are used for
atoms which have them, e.g. %pi.
Default value: 100
tr_optimize_max_loop is the maximum number of times the
macro-expansion and optimization pass of the translator will loop in
considering a form. This is to catch macro expansion errors, and
non-terminating optimization properties.
Default value:
[translate_fast_arrays, tr_function_call_default, tr_bound_function_applyp, tr_array_as_ref, tr_numer, tr_float_can_branch_complex, define_variable]
The list of the switches that affect the form of the translated output. This information is useful to system people when trying to debug the translator. By comparing the translated product to what should have been produced for a given state, it is possible to track down bugs.
Prints a list of warnings which have been given by the translator during the current translation.
Default value: true
- Gives a warning when when function calls are being made which may not be correct due to improper declarations that were made at translate time.
Default value: compfile
- Gives a warning if any FEXPRs are encountered. FEXPRs should not normally be output in translated code, all legitimate special program forms are translated.
Default value: compfile
- Gives a warning if the function meval gets called. If meval is
called that indicates problems in the translation.
Default value: all
- Gives a warning when variables are assigned values inappropriate for their mode.
Default value: compile
- Determines when to send warnings about undeclared variables to the TTY.
Default value: all
- Gives a warning when undefined global variables are seen.
Translates the Maxima file filename into Lisp, and executes the Lisp compiler. The compiled code is not loaded into Maxima.
compile_file returns a list of the names of four files: the original
Maxima file, the Lisp translation, notes on translation, and the compiled code.
If the compilation fails, the fourth item is false.
Some declarations and definitions take effect as soon
as the Lisp code is compiled (without loading the compiled code).
These include functions defined with the := operator,
macros define with the ::= operator,
alias, declare,
define_variable, mode_declare,
and
infix, matchfix,
nofix, postfix, prefix,
and compfile.
Assignments and function calls are not evaluated until the compiled code is
loaded. In particular, within the Maxima file, assignments to the translation
flags (tr_numer, etc.) have no effect on the translation.
filename may not contain :lisp statements.
compile_file evaluates its arguments.
When translating a file of Maxima code
to Lisp, it is important for the translator to know which functions it
sees in the file are to be called as translated or compiled functions,
and which ones are just Maxima functions or undefined. Putting this
declaration at the top of the file, lets it know that although a symbol
does which does not yet have a Lisp function value, will have one at
call time. (MFUNCTION-CALL fn arg1 arg2 ...) is generated when
the translator does not know fn is going to be a Lisp function.
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