/*-*-MACSYMA-*-*/

EVAL_WHEN([TRANSLATE,BATCH,DEMO],
          IF GET('SHAREM,'VERSION) = FALSE
             THEN LOADFILE(AUTOLO,FASL,DSK,SHAREM))$

HERALD_PACKAGE(BASIC)$


/* These are basic macros, nothing in here should call anything
   complicated. PUSH and POP here are the simple version
   which do not hack once-only evaluation. 
   I might say that these macros are around mostly so
   that the code for implementing the more complicated
   macros, including the once-only stuff, can be simpler.
*/

PROG1(STATEMENT1,[STATEMENTS])::=
 BUILDQ([STATEMENT1,STATEMENTS,LOCAL:?GENSYM()],
        LAMBDA([LOCAL],SPLICE(STATEMENTS),LOCAL)(STATEMENT1))$

SYMBOLCHECK(X):=
 IF SYMBOLP(X) THEN X ELSE ERROR("Arg must be a symbol",X)$

PUSH(C,L)::=(SYMBOLCHECK(L),BUILDQ([C,L],L:CONS(C,L)))$

POP(L)::=(SYMBOLCHECK(L),BUILDQ([L],PROG1(FIRST(L),L:REST(L))))$

/* TR_EV is a pretty sorry way to get optimization
   by Translation-time evaluation. User directed constant-folding
   you might call it. TR_EV has other uses. */

TR_EV(X)::=?MEVAL(X)$