[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
34.1 Introduction to Rules and Patterns | ||
34.2 Functions and Variables for Rules and Patterns |
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
This section describes user-defined pattern matching and simplification rules.
There are two groups of functions which implement somewhat different pattern
matching schemes. In one group are tellsimp
, tellsimpafter
,
defmatch
, defrule
, apply1
, applyb1
, and
apply2
. In the other group are let
and letsimp
.
Both schemes define patterns in terms of pattern variables declared by
matchdeclare
.
Pattern-matching rules defined by tellsimp
and tellsimpafter
are
applied automatically by the Maxima simplifier. Rules defined by
defmatch
, defrule
, and let
are applied by an explicit
function call.
There are additional mechanisms for rules applied to polynomials by
tellrat
, and for commutative and noncommutative algebra in affine
package.
Categories: Simplification · Rules and patterns
[ < ] | [ > ] | [ << ] | [ Up ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
Repeatedly applies rule_1 to expr until it fails, then repeatedly applies the same rule to all subexpressions of expr, left to right, until rule_1 has failed on all subexpressions. Call the result of transforming expr in this manner expr_2. Then rule_2 is applied in the same fashion starting at the top of expr_2. When rule_n fails on the final subexpression, the result is returned.
maxapplydepth
is the depth of the deepest subexpressions processed by
apply1
and apply2
.
See also applyb1
, apply2
, and let
.
Categories: Rules and patterns
If rule_1 fails on a given subexpression, then rule_2 is repeatedly applied, etc. Only if all rules fail on a given subexpression is the whole set of rules repeatedly applied to the next subexpression. If one of the rules succeeds, then the same subexpression is reprocessed, starting with the first rule.
maxapplydepth
is the depth of the deepest subexpressions processed by
apply1
and apply2
.
See also apply1
and let
.
Categories: Rules and patterns
Repeatedly applies rule_1 to the deepest subexpression of expr until it fails, then repeatedly applies the same rule one level higher (i.e., larger subexpressions), until rule_1 has failed on the top-level expression. Then rule_2 is applied in the same fashion to the result of rule_1. After rule_n has been applied to the top-level expression, the result is returned.
applyb1
is similar to apply1
but works from
the bottom up instead of from the top down.
maxapplyheight
is the maximum height which applyb1
reaches
before giving up.
See also apply1
, apply2
, and let
.
Categories: Rules and patterns
Default value: default_let_rule_package
current_let_rule_package
is the name of the rule package that is used by
functions in the let
package (letsimp
, etc.) if no other rule package is specified.
This variable may be assigned the name of any rule package defined
via the let
command.
If a call such as letsimp (expr, rule_pkg_name)
is made,
the rule package rule_pkg_name
is used for that function call only,
and the value of current_let_rule_package
is not changed.
Categories: Rules and patterns
Default value: default_let_rule_package
default_let_rule_package
is the name of the rule package used when one
is not explicitly set by the user with let
or by changing the value of
current_let_rule_package
.
Categories: Rules and patterns
Defines a function progname(expr, x_1, ..., x_n)
which tests expr to see if it matches pattern.
pattern is an expression containing the pattern arguments x_1,
…, x_n (if any) and some pattern variables (if any). The pattern
arguments are given explicitly as arguments to defmatch
while the pattern
variables are declared by the matchdeclare
function. Any variable not
declared as a pattern variable in matchdeclare
or as a pattern argument
in defmatch
matches only itself.
The first argument to the created function progname is an expression to be matched against the pattern and the other arguments are the actual arguments which correspond to the dummy variables x_1, …, x_n in the pattern.
If the match is successful, progname returns a list of equations whose
left sides are the pattern arguments and pattern variables, and whose right
sides are the subexpressions which the pattern arguments and variables matched.
The pattern variables, but not the pattern arguments, are assigned the
subexpressions they match. If the match fails, progname returns
false
.
A literal pattern (that is, a pattern which contains neither pattern arguments
nor pattern variables) returns true
if the match succeeds.
See also matchdeclare
, defrule
, tellsimp
, and
tellsimpafter
.
Examples:
Define a function linearp(expr, x)
which
tests expr
to see if it is of the form a*x + b
such that a
and b
do not contain x
and a
is nonzero.
This match function matches expressions which are linear in any variable,
because the pattern argument x
is given to defmatch
.
(%i1) matchdeclare (a, lambda ([e], e#0 and freeof(x, e)), b, freeof(x)); (%o1) done (%i2) defmatch (linearp, a*x + b, x); (%o2) linearp (%i3) linearp (3*z + (y + 1)*z + y^2, z); 2 (%o3) [b = y , a = y + 4, x = z] (%i4) a; (%o4) y + 4 (%i5) b; 2 (%o5) y (%i6) x; (%o6) x
Define a function linearp(expr)
which tests expr
to see if it is of the form a*x + b
such that a
and b
do not contain x
and a
is nonzero.
This match function only matches expressions linear in x
,
not any other variable, because no pattern argument is given to defmatch
.
(%i1) matchdeclare (a, lambda ([e], e#0 and freeof(x, e)), b, freeof(x)); (%o1) done (%i2) defmatch (linearp, a*x + b); (%o2) linearp (%i3) linearp (3*z + (y + 1)*z + y^2); (%o3) false (%i4) linearp (3*x + (y + 1)*x + y^2); 2 (%o4) [b = y , a = y + 4]
Define a function checklimits(expr)
which tests expr
to see if it is a definite integral.
(%i1) matchdeclare ([a, f], true); (%o1) done (%i2) constinterval (l, h) := constantp (h - l); (%o2) constinterval(l, h) := constantp(h - l) (%i3) matchdeclare (b, constinterval (a)); (%o3) done (%i4) matchdeclare (x, atom); (%o4) done (%i5) simp : false; (%o5) false (%i6) defmatch (checklimits, 'integrate (f, x, a, b)); (%o6) checklimits (%i7) simp : true; (%o7) true (%i8) 'integrate (sin(t), t, %pi + x, 2*%pi + x); x + 2 %pi / [ (%o8) I sin(t) dt ] / x + %pi (%i9) checklimits (%); (%o9) [b = x + 2 %pi, a = x + %pi, x = t, f = sin(t)]
Categories: Rules and patterns
Defines and names a replacement rule for the given pattern. If the rule named
rulename is applied to an expression (by apply1
, applyb1
, or
apply2
), every subexpression matching the pattern will be replaced by the
replacement. All variables in the replacement which have been
assigned values by the pattern match are assigned those values in the
replacement which is then simplified.
The rules themselves can be
treated as functions which transform an expression by one
operation of the pattern match and replacement.
If the match fails, the rule function returns false
.
Categories: Rules and patterns
Display rules with the names rulename_1, …, rulename_n,
as returned by defrule
, tellsimp
, or tellsimpafter
,
or a pattern defined by defmatch
.
Each rule is displayed with an intermediate expression label (%t
).
disprule (all)
displays all rules.
disprule
quotes its arguments.
disprule
returns the list of intermediate expression labels corresponding
to the displayed rules.
See also letrules
, which displays rules defined by let
.
Examples:
(%i1) tellsimpafter (foo (x, y), bar (x) + baz (y)); (%o1) [foorule1, false] (%i2) tellsimpafter (x + y, special_add (x, y)); (%o2) [+rule1, simplus] (%i3) defmatch (quux, mumble (x)); (%o3) quux (%i4) disprule (foorule1, "+rule1", quux); (%t4) foorule1 : foo(x, y) -> baz(y) + bar(x) (%t5) +rule1 : y + x -> special_add(x, y) (%t6) quux : mumble(x) -> [] (%o6) [%t4, %t5, %t6] (%i6) ''%; (%o6) [foorule1 : foo(x, y) -> baz(y) + bar(x), +rule1 : y + x -> special_add(x, y), quux : mumble(x) -> []]
Categories: Rules and patterns · Display functions
Defines a substitution rule for letsimp
such that prod is replaced
by repl. prod is a product of positive or negative powers of the
following terms:
letsimp
will search for literally unless previous to calling
letsimp
the matchdeclare
function is used to associate a
predicate with the atom. In this case letsimp
will match the atom to
any term of a product satisfying the predicate.
sin(x)
, n!
, f(x,y)
, etc. As with atoms
above letsimp
will look for a literal match unless matchdeclare
is used to associate a predicate with the argument of the kernel.
A term to a positive power will only match a term having at least that
power. A term to a negative power
on the other hand will only match a term with a power at least as
negative. In the case of negative powers in prod the switch
letrat
must be set to true
.
See also letrat
.
If a predicate is included in the let
function followed by a list of
arguments, a tentative match (i.e. one that would be accepted if the predicate
were omitted) is accepted only if predname (arg_1', ..., arg_n')
evaluates to true
where arg_i' is the value matched to arg_i.
The arg_i may be the name of any atom or the argument of any kernel
appearing in prod.
repl may be any rational expression. If any of the atoms or arguments from prod appear in repl the
appropriate substitutions are made.
The global flag letrat
controls the simplification of quotients by
letsimp
. When letrat
is false
, letsimp
simplifies
the numerator and denominator of expr separately, and does not simplify
the quotient. Substitutions such as n!/n
goes to (n-1)!
then
fail. When letrat
is true
, then the numerator, denominator, and
the quotient are simplified in that order.
These substitution functions allow you to work with several rule packages at
once. Each rule package can contain any number of let
rules and is
referenced by a user-defined name. The command let ([prod,
repl, predname, arg_1, ..., arg_n], package_name)
adds the rule predname to the rule package package_name. The
command letsimp (expr, package_name)
applies the rules in
package_name. letsimp (expr, package_name1,
package_name2, ...)
is equivalent to letsimp (expr,
package_name1)
followed by letsimp (%, package_name2)
,
…
current_let_rule_package
is the name of the rule package that is
presently being used. This variable may be assigned the name of any rule
package defined via the let
command. Whenever any of the functions
comprising the let
package are called with no package name, the package
named by current_let_rule_package
is used. If a call such as
letsimp (expr, rule_pkg_name)
is made, the rule package
rule_pkg_name is used for that letsimp
command only, and
current_let_rule_package
is not changed. If not otherwise specified,
current_let_rule_package
defaults to default_let_rule_package
.
(%i1) matchdeclare ([a, a1, a2], true)$ (%i2) oneless (x, y) := is (x = y-1)$ (%i3) let (a1*a2!, a1!, oneless, a2, a1); (%o3) a1 a2! --> a1! where oneless(a2, a1) (%i4) letrat: true$ (%i5) let (a1!/a1, (a1-1)!); a1! (%o5) --- --> (a1 - 1)! a1 (%i6) letsimp (n*m!*(n-1)!/m); (%o6) (m - 1)! n! (%i7) let (sin(a)^2, 1 - cos(a)^2); 2 2 (%o7) sin (a) --> 1 - cos (a) (%i8) letsimp (sin(x)^4); 4 2 (%o8) cos (x) - 2 cos (x) + 1
Categories: Rules and patterns
Default value: false
When letrat
is false
, letsimp
simplifies the
numerator and denominator of a ratio separately,
and does not simplify the quotient.
When letrat
is true
,
the numerator, denominator, and their quotient are simplified in that order.
(%i1) matchdeclare (n, true)$ (%i2) let (n!/n, (n-1)!); n! (%o2) -- --> (n - 1)! n (%i3) letrat: false$ (%i4) letsimp (a!/a); a! (%o4) -- a (%i5) letrat: true$ (%i6) letsimp (a!/a); (%o6) (a - 1)!
Categories: Rules and patterns
Displays the rules in a rule package.
letrules ()
displays the rules in the current rule package.
letrules (package_name)
displays the rules in package_name.
The current rule package is named by current_let_rule_package
.
If not otherwise specified, current_let_rule_package
defaults to default_let_rule_package
.
See also disprule
, which displays rules defined by tellsimp
and
tellsimpafter
.
Categories: Rules and patterns
Repeatedly applies the substitution rules defined by let
until no further change is made to expr.
letsimp (expr)
uses the rules from current_let_rule_package
.
letsimp (expr, package_name)
uses the rules from
package_name without changing current_let_rule_package
.
letsimp (expr, package_name_1, ..., package_name_n)
is equivalent to letsimp (expr, package_name_1
,
followed by letsimp (%, package_name_2)
, and so on.
Categories: Rules and patterns
Default value: [default_let_rule_package]
let_rule_packages
is a list of all user-defined let rule packages
plus the default package default_let_rule_package
.
Categories: Rules and patterns
Associates a predicate pred_k
with a variable or list of variables a_k
so that a_k matches expressions
for which the predicate returns anything other than false
.
A predicate is the name of a function,
or a lambda expression,
or a function call or lambda call missing the last argument,
or true
or all
.
Any expression matches true
or all
.
If the predicate is specified as a function call or lambda call,
the expression to be tested is appended to the list of arguments;
the arguments are evaluated at the time the match is evaluated.
Otherwise, the predicate is specified as a function name or lambda expression,
and the expression to be tested is the sole argument.
A predicate function need not be defined when matchdeclare
is called;
the predicate is not evaluated until a match is attempted.
A predicate may return a Boolean expression as well as true
or
false
. Boolean expressions are evaluated by is
within the
constructed rule function, so it is not necessary to call is
within the
predicate.
If an expression satisfies a match predicate, the match variable is assigned the
expression, except for match variables which are operands of addition +
or multiplication *
. Only addition and multiplication are handled
specially; other n-ary operators (both built-in and user-defined) are treated
like ordinary functions.
In the case of addition and multiplication, the match variable may be assigned a single expression which satisfies the match predicate, or a sum or product (respectively) of such expressions. Such multiple-term matching is greedy: predicates are evaluated in the order in which their associated variables appear in the match pattern, and a term which satisfies more than one predicate is taken by the first predicate which it satisfies. Each predicate is tested against all operands of the sum or product before the next predicate is evaluated. In addition, if 0 or 1 (respectively) satisfies a match predicate, and there are no other terms which satisfy the predicate, 0 or 1 is assigned to the match variable associated with the predicate.
The algorithm for processing addition and multiplication patterns makes some match results (for example, a pattern in which a "match anything" variable appears) dependent on the ordering of terms in the match pattern and in the expression to be matched. However, if all match predicates are mutually exclusive, the match result is insensitive to ordering, as one match predicate cannot accept terms matched by another.
Calling matchdeclare
with a variable a as an argument changes the
matchdeclare
property for a, if one was already declared; only the
most recent matchdeclare
is in effect when a rule is defined. Later
changes to the matchdeclare
property (via matchdeclare
or
remove
) do not affect existing rules.
propvars (matchdeclare)
returns the list of all variables for which there
is a matchdeclare
property. printprops (a, matchdeclare)
returns the predicate for variable a
.
printprops (all, matchdeclare)
returns the list of predicates for all
matchdeclare
variables. remove (a, matchdeclare)
removes
the matchdeclare
property from a.
The functions defmatch
, defrule
, tellsimp
,
tellsimpafter
, and let
construct rules which test expressions
against patterns.
matchdeclare
quotes its arguments.
matchdeclare
always returns done
.
Examples:
A predicate is the name of a function,
or a lambda expression,
or a function call or lambda call missing the last argument,
or true
or all
.
(%i1) matchdeclare (aa, integerp); (%o1) done (%i2) matchdeclare (bb, lambda ([x], x > 0)); (%o2) done (%i3) matchdeclare (cc, freeof (%e, %pi, %i)); (%o3) done (%i4) matchdeclare (dd, lambda ([x, y], gcd (x, y) = 1) (1728)); (%o4) done (%i5) matchdeclare (ee, true); (%o5) done (%i6) matchdeclare (ff, all); (%o6) done
If an expression satisfies a match predicate, the match variable is assigned the expression.
(%i1) matchdeclare (aa, integerp, bb, atom); (%o1) done (%i2) defrule (r1, bb^aa, ["integer" = aa, "atom" = bb]); aa (%o2) r1 : bb -> [integer = aa, atom = bb] (%i3) r1 (%pi^8); (%o3) [integer = 8, atom = %pi]
In the case of addition and multiplication, the match variable may be assigned a single expression which satisfies the match predicate, or a sum or product (respectively) of such expressions.
(%i1) matchdeclare (aa, atom, bb, lambda ([x], not atom(x))); (%o1) done (%i2) defrule (r1, aa + bb, ["all atoms" = aa, "all nonatoms" = bb]); bb + aa partitions `sum' (%o2) r1 : bb + aa -> [all atoms = aa, all nonatoms = bb] (%i3) r1 (8 + a*b + sin(x)); (%o3) [all atoms = 8, all nonatoms = sin(x) + a b] (%i4) defrule (r2, aa * bb, ["all atoms" = aa, "all nonatoms" = bb]); bb aa partitions `product' (%o4) r2 : aa bb -> [all atoms = aa, all nonatoms = bb] (%i5) r2 (8 * (a + b) * sin(x)); (%o5) [all atoms = 8, all nonatoms = (b + a) sin(x)]
When matching arguments of +
and *
,
if all match predicates are mutually exclusive,
the match result is insensitive to ordering,
as one match predicate cannot accept terms matched by another.
(%i1) matchdeclare (aa, atom, bb, lambda ([x], not atom(x))); (%o1) done (%i2) defrule (r1, aa + bb, ["all atoms" = aa, "all nonatoms" = bb]); bb + aa partitions `sum' (%o2) r1 : bb + aa -> [all atoms = aa, all nonatoms = bb] (%i3) r1 (8 + a*b + %pi + sin(x) - c + 2^n); n (%o3) [all atoms = %pi + 8, all nonatoms = sin(x) + 2 - c + a b] (%i4) defrule (r2, aa * bb, ["all atoms" = aa, "all nonatoms" = bb]); bb aa partitions `product' (%o4) r2 : aa bb -> [all atoms = aa, all nonatoms = bb] (%i5) r2 (8 * (a + b) * %pi * sin(x) / c * 2^n); n (b + a) 2 sin(x) (%o5) [all atoms = 8 %pi, all nonatoms = -----------------] c
The functions propvars
and printprops
return information about
match variables.
(%i1) matchdeclare ([aa, bb, cc], atom, [dd, ee], integerp); (%o1) done (%i2) matchdeclare (ff, floatnump, gg, lambda ([x], x > 100)); (%o2) done (%i3) propvars (matchdeclare); (%o3) [aa, bb, cc, dd, ee, ff, gg] (%i4) printprops (ee, matchdeclare); (%o4) [integerp(ee)] (%i5) printprops (gg, matchdeclare); (%o5) [lambda([x], x > 100, gg)] (%i6) printprops (all, matchdeclare); (%o6) [lambda([x], x > 100, gg), floatnump(ff), integerp(ee), integerp(dd), atom(cc), atom(bb), atom(aa)]
Categories: Rules and patterns · Declarations and inferences
Default value: 10000
maxapplydepth
is the maximum depth to which apply1
and apply2
will delve.
Categories: Function application
Default value: 10000
maxapplyheight
is the maximum height to which applyb1
will reach before giving up.
Categories: Function application
Deletes the substitution rule, prod -> repl, most
recently defined by the let
function. If name is supplied the rule is
deleted from the rule package name.
remlet()
and remlet(all)
delete all substitution rules from the
current rule package. If the name of a rule package is supplied, e.g.
remlet (all, name)
, the rule package name is also deleted.
If a substitution is to be changed using the same
product, remlet
need not be called, just redefine the substitution
using the same product (literally) with the let
function and the new
replacement and/or predicate name. Should remlet (prod)
now be
called the original substitution rule is revived.
See also remrule
, which removes a rule defined by tellsimp
or
tellsimpafter
.
Categories: Rules and patterns
Removes rules defined by tellsimp
or tellsimpafter
.
remrule (op, rulename)
removes the rule with the name rulename from the operator op.
When op is a built-in or user-defined operator
(as defined by infix
, prefix
, etc.),
op and rulename must be enclosed in double quote marks.
remrule (op, all)
removes all rules for the operator op.
See also remlet
, which removes a rule defined by let
.
Examples:
(%i1) tellsimp (foo (aa, bb), bb - aa); (%o1) [foorule1, false] (%i2) tellsimpafter (aa + bb, special_add (aa, bb)); (%o2) [+rule1, simplus] (%i3) infix ("@@"); (%o3) @@ (%i4) tellsimp (aa @@ bb, bb/aa); (%o4) [@@rule1, false] (%i5) tellsimpafter (quux (%pi, %e), %pi - %e); (%o5) [quuxrule1, false] (%i6) tellsimpafter (quux (%e, %pi), %pi + %e); (%o6) [quuxrule2, quuxrule1, false] (%i7) [foo (aa, bb), aa + bb, aa @@ bb, quux (%pi, %e), quux (%e, %pi)]; bb (%o7) [bb - aa, special_add(aa, bb), --, %pi - %e, %pi + %e] aa (%i8) remrule (foo, foorule1); (%o8) foo (%i9) remrule ("+", ?\+rule1); (%o9) + (%i10) remrule ("@@", ?\@\@rule1); (%o10) @@ (%i11) remrule (quux, all); (%o11) quux (%i12) [foo (aa, bb), aa + bb, aa @@ bb, quux (%pi, %e), quux (%e, %pi)]; (%o12) [foo(aa, bb), bb + aa, aa @@ bb, quux(%pi, %e), quux(%e, %pi)]
Categories: Rules and patterns
is similar to tellsimpafter
but places
new information before old so that it is applied before the built-in
simplification rules.
tellsimp
is used when it is important to modify
the expression before the simplifier works on it, for instance if the
simplifier "knows" something about the expression, but what it returns
is not to your liking.
If the simplifier "knows" something about the
main operator of the expression, but is simply not doing enough for
you, you probably want to use tellsimpafter
.
The pattern may not be a sum, product, single variable, or number.
The system variable rules
is the list of rules defined by
defrule
, defmatch
, tellsimp
, and tellsimpafter
.
Examples:
(%i1) matchdeclare (x, freeof (%i)); (%o1) done (%i2) %iargs: false$ (%i3) tellsimp (sin(%i*x), %i*sinh(x)); (%o3) [sinrule1, simp-%sin] (%i4) trigexpand (sin (%i*y + x)); (%o4) sin(x) cos(%i y) + %i cos(x) sinh(y) (%i5) %iargs:true$ (%i6) errcatch(0^0); 0 0 has been generated (%o6) [] (%i7) ev (tellsimp (0^0, 1), simp: false); (%o7) [^rule1, simpexpt] (%i8) 0^0; (%o8) 1 (%i9) remrule ("^", %th(2)[1]); (%o9) ^ (%i10) tellsimp (sin(x)^2, 1 - cos(x)^2); (%o10) [^rule2, simpexpt] (%i11) (1 + sin(x))^2; 2 (%o11) (sin(x) + 1) (%i12) expand (%); 2 (%o12) 2 sin(x) - cos (x) + 2 (%i13) sin(x)^2; 2 (%o13) 1 - cos (x) (%i14) kill (rules); (%o14) done (%i15) matchdeclare (a, true); (%o15) done (%i16) tellsimp (sin(a)^2, 1 - cos(a)^2); (%o16) [^rule3, simpexpt] (%i17) sin(y)^2; 2 (%o17) 1 - cos (y)
Categories: Rules and patterns
Defines a simplification rule which the Maxima simplifier applies after built-in
simplification rules. pattern is an expression, comprising pattern
variables (declared by matchdeclare
) and other atoms and operators,
considered literals for the purpose of pattern matching. replacement is
substituted for an actual expression which matches pattern; pattern
variables in replacement are assigned the values matched in the actual
expression.
pattern may be any nonatomic expression in which the main operator is not
a pattern variable; the simplification rule is associated with the main
operator. The names of functions (with one exception, described below), lists,
and arrays may appear in pattern as the main operator only as literals
(not pattern variables); this rules out expressions such as aa(x)
and
bb[y]
as patterns, if aa
and bb
are pattern variables.
Names of functions, lists, and arrays which are pattern variables may appear as
operators other than the main operator in pattern.
There is one exception to the above rule concerning names of functions.
The name of a subscripted function in an expression such as aa[x](y)
may be a pattern variable, because the main operator is not aa
but rather
the Lisp atom mqapply
. This is a consequence of the representation of
expressions involving subscripted functions.
Simplification rules are applied after evaluation
(if not suppressed through quotation or the flag noeval
).
Rules established by tellsimpafter
are applied in the order they were
defined, and after any built-in rules.
Rules are applied bottom-up, that is,
applied first to subexpressions before application to the whole expression.
It may be necessary to repeatedly simplify a result (for example, via the
quote-quote operator ''
or the flag infeval
)
to ensure that all rules are applied.
Pattern variables are treated as local variables in simplification rules.
Once a rule is defined, the value of a pattern variable
does not affect the rule, and is not affected by the rule.
An assignment to a pattern variable which results from a successful rule match
does not affect the current assignment (or lack of it) of the pattern variable.
However, as with all atoms in Maxima, the properties of pattern variables (as
declared by put
and related functions) are global.
The rule constructed by tellsimpafter
is named after the main operator of
pattern. Rules for built-in operators, and user-defined operators defined
by infix
, prefix
, postfix
, matchfix
, and
nofix
, have names which are Lisp identifiers.
Rules for other functions have names which are Maxima identifiers.
The treatment of noun and verb forms is slightly confused. If a rule is defined for a noun (or verb) form and a rule for the corresponding verb (or noun) form already exists, the newly-defined rule applies to both forms (noun and verb). If a rule for the corresponding verb (or noun) form does not exist, the newly-defined rule applies only to the noun (or verb) form.
The rule constructed by tellsimpafter
is an ordinary Lisp function.
If the name of the rule is $foorule1
,
the construct :lisp (trace $foorule1)
traces the function,
and :lisp (symbol-function '$foorule1)
displays its definition.
tellsimpafter
quotes its arguments.
tellsimpafter
returns the list of rules for the main operator of
pattern, including the newly established rule.
See also matchdeclare
, defmatch
, defrule
, tellsimp
,
let
, kill
, remrule
, and clear_rules
.
Examples:
pattern may be any nonatomic expression in which the main operator is not a pattern variable.
(%i1) matchdeclare (aa, atom, [ll, mm], listp, xx, true)$ (%i2) tellsimpafter (sin (ll), map (sin, ll)); (%o2) [sinrule1, simp-%sin] (%i3) sin ([1/6, 1/4, 1/3, 1/2, 1]*%pi); 1 sqrt(2) sqrt(3) (%o3) [-, -------, -------, 1, 0] 2 2 2 (%i4) tellsimpafter (ll^mm, map ("^", ll, mm)); (%o4) [^rule1, simpexpt] (%i5) [a, b, c]^[1, 2, 3]; 2 3 (%o5) [a, b , c ] (%i6) tellsimpafter (foo (aa (xx)), aa (foo (xx))); (%o6) [foorule1, false] (%i7) foo (bar (u - v)); (%o7) bar(foo(u - v))
Rules are applied in the order they were defined. If two rules can match an expression, the rule which was defined first is applied.
(%i1) matchdeclare (aa, integerp); (%o1) done (%i2) tellsimpafter (foo (aa), bar_1 (aa)); (%o2) [foorule1, false] (%i3) tellsimpafter (foo (aa), bar_2 (aa)); (%o3) [foorule2, foorule1, false] (%i4) foo (42); (%o4) bar_1(42)
Pattern variables are treated as local variables in simplification rules.
(Compare to defmatch
, which treats pattern variables as global
variables.)
(%i1) matchdeclare (aa, integerp, bb, atom); (%o1) done (%i2) tellsimpafter (foo(aa, bb), bar('aa=aa, 'bb=bb)); (%o2) [foorule1, false] (%i3) bb: 12345; (%o3) 12345 (%i4) foo (42, %e); (%o4) bar(aa = 42, bb = %e) (%i5) bb; (%o5) 12345
As with all atoms, properties of pattern variables are global even though values
are local. In this example, an assignment property is declared via
define_variable
. This is a property of the atom bb
throughout
Maxima.
(%i1) matchdeclare (aa, integerp, bb, atom); (%o1) done (%i2) tellsimpafter (foo(aa, bb), bar('aa=aa, 'bb=bb)); (%o2) [foorule1, false] (%i3) foo (42, %e); (%o3) bar(aa = 42, bb = %e) (%i4) define_variable (bb, true, boolean); (%o4) true (%i5) foo (42, %e); Error: bb was declared mode boolean, has value: %e -- an error. Quitting. To debug this try debugmode(true);
Rules are named after main operators. Names of rules for built-in and user-defined operators are Lisp identifiers, while names for other functions are Maxima identifiers.
(%i1) tellsimpafter (foo (%pi + %e), 3*%pi); (%o1) [foorule1, false] (%i2) tellsimpafter (foo (%pi * %e), 17*%e); (%o2) [foorule2, foorule1, false] (%i3) tellsimpafter (foo (%i ^ %e), -42*%i); (%o3) [foorule3, foorule2, foorule1, false] (%i4) tellsimpafter (foo (9) + foo (13), quux (22)); (%o4) [+rule1, simplus] (%i5) tellsimpafter (foo (9) * foo (13), blurf (22)); (%o5) [*rule1, simptimes] (%i6) tellsimpafter (foo (9) ^ foo (13), mumble (22)); (%o6) [^rule1, simpexpt] (%i7) rules; (%o7) [foorule1, foorule2, foorule3, +rule1, *rule1, ^rule1] (%i8) foorule_name: first (%o1); (%o8) foorule1 (%i9) plusrule_name: first (%o4); (%o9) +rule1 (%i10) remrule (foo, foorule1); (%o10) foo (%i11) remrule ("^", ?\^rule1); (%o11) ^ (%i12) rules; (%o12) [foorule2, foorule3, +rule1, *rule1]
A worked example: anticommutative multiplication.
(%i1) gt (i, j) := integerp(j) and i < j; (%o1) gt(i, j) := integerp(j) and i < j (%i2) matchdeclare (i, integerp, j, gt(i)); (%o2) done (%i3) tellsimpafter (s[i]^^2, 1); (%o3) [^^rule1, simpncexpt] (%i4) tellsimpafter (s[i] . s[j], -s[j] . s[i]); (%o4) [.rule1, simpnct] (%i5) s[1] . (s[1] + s[2]); (%o5) s . (s + s ) 1 2 1 (%i6) expand (%); (%o6) 1 - s . s 2 1 (%i7) factor (expand (sum (s[i], i, 0, 9)^^5)); (%o7) 100 (s + s + s + s + s + s + s + s + s + s ) 9 8 7 6 5 4 3 2 1 0
Categories: Rules and patterns
Executes kill (rules)
and then resets the next rule number to 1
for addition +
, multiplication *
, and exponentiation ^
.
Categories: Rules and patterns
[ << ] | [ >> ] | [Top] | [Contents] | [Index] | [ ? ] |
This document was generated by Oliver Kullmann on May, 18 2013 using texi2html 1.76.