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The directory maxima/share/simplification contains several scripts
which implement simplification rules and functions,
and also some functions not related to simplification.
Next: Package facexp, Previous: Introduction to simplification, Up: Package simplification [Contents][Index]
The absimp package contains pattern-matching rules that
extend the built-in simplification rules for the abs and signum
functions.
absimp respects relations
established with the built-in assume function and by declarations such
as mode_declare (m, even, n, odd) for even or odd integers.
absimp defines unitramp and unitstep functions
in terms of abs and signum.
load ("absimp") loads this package.
demo ("absimp") shows a demonstration of this package.
Examples:
(%i1) load ("absimp")$
(%i2) (abs (x))^2;
2
(%o2) x
(%i3) diff (abs (x), x);
x
(%o3) ------
abs(x)
(%i4) cosh (abs (x)); (%o4) cosh(x)
Next: Package functs, Previous: Package absimp, Up: Package simplification [Contents][Index]
The facexp package contains several related functions that
provide the user with the ability to structure expressions by controlled
expansion. This capability is especially useful when the expression
contains variables that have physical meaning, because it is often true
that the most economical form of such an expression can be obtained by
fully expanding the expression with respect to those variables, and then
factoring their coefficients. While it is true that this procedure is
not difficult to carry out using standard Maxima functions, additional
fine-tuning may also be desirable, and these finishing touches can be
more difficult to apply.
The function facsum and its related forms
provide a convenient means for controlling the structure of expressions
in this way. Another function, collectterms, can be used to add two or
more expressions that have already been simplified to this form, without
resimplifying the whole expression again. This function may be
useful when the expressions are very large.
load ("facexp") loads this package.
demo ("facexp") shows a demonstration of this package.
Returns a form of expr which depends on the
arguments arg_1, ..., arg_n.
The arguments can be any form suitable for ratvars, or they can be
lists of such forms. If the arguments are not lists, then the form
returned is fully expanded with respect to the arguments, and the
coefficients of the arguments are factored. These coefficients are
free of the arguments, except perhaps in a non-rational sense.
If any of the arguments are lists, then all such lists are combined
into a single list, and instead of calling factor on the
coefficients of the arguments, facsum calls itself on these
coefficients, using this newly constructed single list as the new
argument list for this recursive call. This process can be repeated to
arbitrary depth by nesting the desired elements in lists.
It is possible that one may wish to facsum with respect to more
complicated subexpressions, such as log (x + y). Such arguments are
also permissible.
Occasionally the user may wish to obtain any of the above forms
for expressions which are specified only by their leading operators.
For example, one may wish to facsum with respect to all log’s. In
this situation, one may include among the arguments either the specific
log’s which are to be treated in this way, or alternatively, either
the expression operator (log) or 'operator (log). If one wished to
facsum the expression expr with respect to the operators op_1, ..., op_n,
one would evaluate facsum (expr, operator (op_1, ..., op_n)).
The operator form may also appear inside list arguments.
In addition, the setting of the switches facsum_combine and
nextlayerfactor may affect the result of facsum.
Default value: false
When nextlayerfactor is true, recursive calls of facsum
are applied to the factors of the factored form of the
coefficients of the arguments.
When false, facsum is applied to
each coefficient as a whole whenever recursive calls to facsum occur.
Inclusion of the atom
nextlayerfactor in the argument list of facsum has the effect of
nextlayerfactor: true, but for the next level of the expression only.
Since nextlayerfactor is always bound to either true or false, it
must be presented single-quoted whenever it appears in the argument list of facsum.
Default value: true
facsum_combine controls the form of the final result returned by
facsum when its argument is a quotient of polynomials. If
facsum_combine is false then the form will be returned as a fully
expanded sum as described above, but if true, then the expression
returned is a ratio of polynomials, with each polynomial in the form
described above.
The true setting of this switch is useful when one
wants to facsum both the numerator and denominator of a rational
expression, but does not want the denominator to be multiplied
through the terms of the numerator.
Returns a form of expr which is
obtained by calling facsum on the factors of expr with arg_1, ... arg_n as
arguments. If any of the factors of expr is raised to a power, both
the factor and the exponent will be processed in this way.
Collects all terms that contain arg_1 ... arg_n.
If several expressions have been simplified with the following functions
facsum, factorfacsum, factenexpand, facexpten or
factorfacexpten, and they are to be added together, it may be desirable
to combine them using the function collecterms. collecterms can
take as arguments all of the arguments that can be given to these other
associated functions with the exception of nextlayerfactor, which has no
effect on collectterms. The advantage of collectterms is that it
returns a form similar to facsum, but since it is adding forms that have
already been processed by facsum, it does not need to repeat that effort.
This capability is especially useful when the expressions to be summed are very
large.
See also factor.
Example:
(%i1) (exp(x)+2)*x+exp(x);
x x
(%o1) x (%e + 2) + %e
(%i2) collectterms(expand(%),exp(x));
x
(%o2) (x + 1) %e + 2 x
Next: Package ineq, Previous: Package facexp, Up: Package simplification [Contents][Index]
Removes part n from the expression expr.
If n is a list of the form [l, m]
then parts l thru m are removed.
To use this function write first load("functs").
Returns the Wronskian matrix of the list of expressions [f_1, ..., f_n] in the variable x. The determinant of the Wronskian matrix is the Wronskian determinant of the list of expressions.
To use wronskian, first load("functs"). Example:
(%i1) load ("functs")$
(%i2) wronskian([f(x), g(x)],x);
[ f(x) g(x) ]
[ ]
(%o2) [ d d ]
[ -- (f(x)) -- (g(x)) ]
[ dx dx ]
Returns the trace (sum of the diagonal elements) of matrix M.
To use this function write first load("functs").
Multiplies numerator and denominator of z by the complex conjugate of denominator, thus rationalizing the denominator. Returns canonical rational expression (CRE) form if given one, else returns general form.
To use this function write first load("functs").
Returns true if expr is nonzero and freeof (x, expr) returns true.
Returns false otherwise.
To use this function write first load("functs").
When expr is an expression of the form a*x + b
where a is nonzero, and a and b are free of x,
linear returns a list of three equations, one for each of the three formal
variables b, a, and x. Otherwise, linear returns false.
load("antid") loads this function.
Example:
(%i1) load ("antid");
(%o1) /maxima/share/integration/antid.mac
(%i2) linear ((1 - w)*(1 - x)*z, z);
(%o2) [bargumentb = 0, aargumenta = (w - 1) x - w + 1,
xargumentx = z]
(%i3) linear (cos(u - v) + cos(u + v), u); (%o3) false
When the option variable takegcd is true which is the default,
gcdivide divides the polynomials p and q by their greatest
common divisor and returns the ratio of the results. gcdivde calls the
function ezgcd to divide the polynomials by the greatest common divisor.
When takegcd is false, gcdivide returns the ratio
p/q.
To use this function write first load("functs").
See also ezgcd, gcd, gcdex, and
poly_gcd.
Example:
(%i1) load("functs")$
(%i2) p1:6*x^3+19*x^2+19*x+6;
3 2
(%o2) 6 x + 19 x + 19 x + 6
(%i3) p2:6*x^5+13*x^4+12*x^3+13*x^2+6*x;
5 4 3 2
(%o3) 6 x + 13 x + 12 x + 13 x + 6 x
(%i4) gcdivide(p1, p2);
x + 1
(%o4) ------
3
x + x
(%i5) takegcd:false;
(%o5) false
(%i6) gcdivide(p1, p2);
3 2
6 x + 19 x + 19 x + 6
(%o6) ----------------------------------
5 4 3 2
6 x + 13 x + 12 x + 13 x + 6 x
(%i7) ratsimp(%);
x + 1
(%o7) ------
3
x + x
Returns the n-th term of the arithmetic series
a, a + d, a + 2*d, ..., a + (n - 1)*d.
To use this function write first load("functs").
Returns the n-th term of the geometric series
a, a*r, a*r^2, ..., a*r^(n - 1).
To use this function write first load("functs").
Returns the n-th term of the harmonic series
a/b, a/(b + c), a/(b + 2*c), ..., a/(b + (n - 1)*c).
To use this function write first load("functs").
Returns the sum of the arithmetic series from 1 to n.
To use this function write first load("functs").
Returns the sum of the geometric series from 1 to n. If n is
infinity (inf) then a sum is finite only if the absolute value
of r is less than 1.
To use this function write first load("functs").
Returns the Gaussian probability function
%e^(-x^2/2) / sqrt(2*%pi).
To use this function write first load("functs").
Returns the Gudermannian function
2*atan(%e^x)-%pi/2.
To use this function write first load("functs").
Returns the inverse Gudermannian function
log (tan (%pi/4 + x/2)).
To use this function write first load("functs").
Returns the versed sine 1 - cos (x).
To use this function write first load("functs").
Returns the coversed sine 1 - sin (x).
To use this function write first load("functs").
Returns the exsecant sec (x) - 1.
To use this function write first load("functs").
Returns the haversine (1 - cos(x))/2.
To use this function write first load("functs").
Returns the number of combinations of n objects taken r at a time.
To use this function write first load("functs").
Returns the number of permutations of r objects selected from a set of n objects.
To use this function write first load("functs").
Next: Package rducon, Previous: Package functs, Up: Package simplification [Contents][Index]
The ineq package contains simplification rules
for inequalities.
Example session:
(%i1) load("ineq")$
tellsimp: warning: rule will treat '+
' as noncommutative and nonassociative.
tellsimp: warning: rule will treat '+
' as noncommutative and nonassociative.
tellsimp: warning: rule will treat '+
' as noncommutative and nonassociative.
tellsimp: warning: rule will treat '+
' as noncommutative and nonassociative.
tellsimp: warning: rule will treat '+
' as noncommutative and nonassociative.
tellsimp: warning: rule will treat '+
' as noncommutative and nonassociative.
tellsimp: warning: rule will treat '+
' as noncommutative and nonassociative.
tellsimp: warning: rule will treat '+
' as noncommutative and nonassociative.
(%i2) a>=4; /* a sample inequality */
(%o2) a >= 4
(%o3) b + a > c + 4
(%o4) 7 x < 7 y
(%o5) - 2 x <= - 6 z
2
(%o6) 1 <= a + 1
(%o8) 2 x < 3 x
(%o9) a >= b
(%o10) a + 3 >= b + 3
(%o11) a >= b
(%o12) a >= c - b
(%o13) b + a >= c
(%o14) (- c) + b + a >= 0
(%o15) c - b - a <= 0
2
(%o16) (z - 1) > - 2 z
2
(%o17) z + 1 > 0
(%o18) true
(%i19) (b>c)+%; /* add a second, strict inequality */
Be careful about using parentheses
around the inequalities: when the user types in (A > B) + (C = 5) the
result is A + C > B + 5, but A > B + C = 5 is a syntax error,
and (A > B + C) = 5 is something else entirely.
Do disprule (all) to see a complete listing
of the rule definitions.
The user will be queried if Maxima is unable to decide the sign of a quantity multiplying an inequality.
The most common mis-feature is illustrated by:
(%i1) eq: a > b; (%o1) a > b
(%i2) 2*eq; (%o2) 2 (a > b)
(%i3) % - eq; (%o3) a > b
Another problem is 0 times an inequality; the default to have this
turn into 0 has been left alone. However, if you type
X*some_inequality and Maxima asks about the sign of X and you
respond zero (or z), the program returns X*some_inequality
and not use the information that X is 0. You should do ev (%, x: 0) in such
a case, as the database will only be used for comparison purposes
in decisions, and not for the purpose of evaluating X.
The user may note a slower response when this package is loaded, as
the simplifier is forced to examine more rules than without the
package, so you might wish to remove the rules after making use of
them. Do kill (rules) to eliminate all of the rules (including any
that you might have defined); or you may be more selective by
killing only some of them; or use remrule on a specific rule.
Note that if you load this package after defining your own
rules you will clobber your rules that have the same name. The
rules in this package are:
*rule1, ..., *rule8,
+rule1, ..., +rule18,
and you must enclose the rulename in quotes to refer to it, as
in remrule ("+", "+rule1") to specifically remove the first rule on "+"
or disprule ("*rule2") to display the definition of the second multiplicative rule.
Next: Package scifac, Previous: Package ineq, Up: Package simplification [Contents][Index]
Replaces constant subexpressions of expr with
constructed constant atoms, saving the definition of all these
constructed constants in the list of equations const_eqns, and
returning the modified expr. Those parts of expr are constant which
return true when operated on by the function constantp. Hence,
before invoking reduce_consts, one should do
declare ([objects to be given the constant property], constant)$
to set up a database of the constant quantities occurring in your expressions.
If you are planning to generate Fortran output after these symbolic calculations, one of the first code sections should be the calculation of all constants. To generate this code segment, do
map ('fortran, const_eqns)$
Variables besides const_eqns which affect reduce_consts are:
const_prefix (default value: xx) is the string of characters used to prefix all
symbols generated by reduce_consts to represent constant subexpressions.
const_counter (default value: 1) is the integer index used to generate unique
symbols to represent each constant subexpression found by reduce_consts.
load ("rducon") loads this function.
demo ("rducon") shows a demonstration of this function.
Previous: Package rducon, Up: Package simplification [Contents][Index]
gcfac is a factoring function that attempts to apply the same heuristics which
scientists apply in trying to make expressions simpler. gcfac is limited
to monomial-type factoring. For a sum, gcfac does the following:
Item (3) does not necessarily do an optimal job of pairwise factoring because of the combinatorially-difficult nature of finding which of all possible rearrangements of the pairs yields the most compact pair-factored result.
load ("scifac") loads this function.
demo ("scifac") shows a demonstration of this function.
Next: Package solve_rec, Previous: Package simplex [Contents][Index]