Fix variable name collision in any_listp which surfaces in algebraic_equivalence when an atom is both a function name and a variable name.

Author: sangwinc

stack/maxima/assessment.mac

@@ -184,13 +184,13 @@ select_apply([ex1]) := block([f1, ex, s1],
 /* ********************************** */
 
 /* True if and only if ex is in the list l. */
-element_listp(ex, l) := any_listp(lambda([ex2], is(ex2=ex)), l)$
+element_listp(ex, _l) := any_listp(lambda([ex2], is(ex2=ex)), _l)$
 
 /* all_listp(p,l) true if all elements of l satisfy p. */
-all_listp(p, l) := if listp(l) then apply("and", maplist(p, l)) else error("all_listp expects its argument to be a list.")$
+all_listp(_p, _l) := if listp(_l) then apply("and", maplist(_p, _l)) else error("all_listp expects its argument to be a list.")$
 
 /* any_listp(p,l) true if all elements of l satisfy p. */
-any_listp(p, l) := if listp(l) then apply("or", maplist(p, l)) else error("any_listp expects its argument to be a list.")$
+any_listp(_p, _l) := if listp(_l) then apply("or", maplist(_p, _l)) else error("any_listp expects its argument to be a list.")$
 
 /* Returns true iff a and b are lists (not necessarily same length) with one or more common elements, false o/w. */
 listsoverlap(a, b) := not(emptyp(intersection(setify(a), setify(b))))$
@@ -199,10 +199,10 @@ listsoverlap(a, b) := not(emptyp(intersection(setify(a), setify(b))))$
 listscontain(a, b, v) := elementp(v, intersection(setify(a), setify(b)))$
 
 /* Removes the first occurance of ex from the list l. */
-removeonce(ex, l) := block(
-  if listp(l)#true or emptyp(l) then return([]),
-  if first(l)=ex then return(rest(l)),
-  append([first(l)], removeonce(ex,rest(l)))
+removeonce(ex, _l) := block(
+  if listp(_l)#true or emptyp(_l) then return([]),
+  if first(_l)=ex then return(rest(_l)),
+  append([first(_l)], removeonce(ex,rest(_l)))
 )$
 
 /* All the elements of l1, which do not occur in l2.  Removes all occurances from l1, not one at a time. */
@@ -974,6 +974,7 @@ texput(binomial, binomialtex);
    24/11/13.  Avoid fullratsimp.  This expands out exprsssions such as (x+a)^6000, which results in an overflow.
    04/01/19.  Avoid trigexpand too soon, i.e. before trying to factor.
    24/02/20.  Using a lambda expression is causing an infinite loop.  Use a named function: algebraic_equivalence_zero.
+   25/04/10.  Change any_listp args to prevent an infinite loop.
 */
 
 algebraic_equivalence_zero(ex) := algebraic_equivalence(ex, 0)$
@@ -1034,6 +1035,7 @@ algebraic_equivalence(SA, SB) :=
        ex:[ex],
     if ex=[] then error("algebraic_equivalence: factoring the difference of two expressions threw an error."),
     ex:ex[1],
+    if ex=0 then return(true),
     /* Try to return a negative result without expanding anything! */
     if safe_op(ex)="-" then
        ex:first(args(ex)),

tests/fixtures/answertestfixtures.class.php

@@ -524,6 +524,8 @@ class stack_answertest_test_data {
         ['AlgEquiv', '', 'g(x):=x^2', 'f(x):=x^2', 0, 'ATFunction_wrongname. ATFunction_true.', ''],
         ['AlgEquiv', '', 'f(y):=y^2', 'f(x):=x^2', 1, 'ATFunction_arguments_different. ATFunction_true.', ''],
         ['AlgEquiv', '', 'f(a,b):=a^2+b^2', 'f(x,y):=x^2+y^2', 1, 'ATFunction_arguments_different. ATFunction_true.', ''],
+        // F appears as both a variable and as a function name.
+        ['AlgEquiv', '', '-30*F', '6*F(l-5*x)', 0, '', ''],
 
         ['AlgEquiv', '', '1', 'x>1', 0, 'ATAlgEquiv_SA_not_inequality.', 'Inequalities'],
         ['AlgEquiv', '', 'x=1', 'x>1 and x<5', 0, 'ATAlgEquiv_TA_not_equation.', ''],