/usr/share/maxima/5.32.1/demo/macex.dem is in maxima 5.32.1-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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/* file: macex.dem */
/* At some point, we get the message: DISPLACE undefined */
/* This is a demo of Macsyma's macroexpanding commands and the use of
the macroexpansion switch. */
(showtime:all,macroexpansion:false)$
/* First we need a macro to play with. Let's define a caseq statement
of the form:
caseq(<var>,[<keys1>],<stmt1>,
[<keys2>],<stmt2>,
....,
[<keysn>],<stmtn>)
where the first <stmt> that has <var> as a member of the associated
<keys> is the one chosen to execute. */
caseq(var,[pairs])::=
if length(pairs)<=2
then buildq([var,keys:first(pairs),statement:last(pairs)],
if member(var,'keys) then statement)
else buildq([var,keys:first(pairs),
statement:first(rest(pairs)),
pairs:rest(rest(pairs))],
if member(var,'keys)
then statement
else caseq(var,splice(pairs)))$
/* let's use our caseq macro to define a simple predicate. */
variablep(x)::=buildq([x],caseq(x,[a,b,c,d,e],true));
/* to make sure it works. */
display(variablep(var1),variablep(var2)),var1:'a,var2:'z;
/* we can see what variablep is expanding into. */
macroexpand(variablep(some_form));
/* we can also watch the expansion by stages. */
macroexpand1(variablep(some_form));
macroexpand1(''%);
/* we might also create simple typep macro using caseq. */
typep(x)::=buildq([x],caseq(x,[1,2,3,4,5,6,7,8,9,0], 'digit,
[a,b,c,d,e,f,g,h,i,j], 'variable,
["+","-","*","/","^"], 'operator))$
/* let's see what things are expanding into. */
macroexpand(typep(test));
/* the nested caseq doesn't expand because macroexpand and
macroexpand1 only look at the top level function. to expand all
levels we can do: */
scanmap('macroexpand,'(typep(test)));
/* let's test it just to make sure it works. */
ev(%,test="*");
/* compare the time it just took to evaluate the macro when expanded
to the time it takes to expand it from scratch and then eval. */
ev(typep(test),test="*");
/* this is why we can save time by using the macroexpansion switch. */
form:'(typep(a));
ev(form);
macroexpansion:expand;
ev(form);
/* there's no savings on the first call after macroexpansion has been
reset, but there is on all subsequent calls. */
ev(form);
/* macroexpand also uses the saved expansion. */
macroexpand(''form);
/* note that form still displays nicely. */
form;
/* if we set macroexpansion to displace however, each macro call will
be completely replaced by the equivalent code. */
/* (macroexpansion:displace,ev(form));
form;
*/
/* note that once the call is displaced, the original call cannot be
retrieved by resetting macroexpansion. */
/* (macroexpansion:false,ev(form));
form;
*/
showtime:false$
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