Editing M-expression (section)

== Examples ==

The definitions for the functions apply and eval from the Lisp 1.5 Manual, page 13.

 apply[fn;x;a] =
    [atom[fn] →
        [eq[fn;CAR] → caar[x];
         eq[fn;CDR] → cdar[x];
         eq[fn;CONS] → cons[car[x];cadr[x]];
         eq[fn;ATOM] → atom[car[x]];
         eq[fn;EQ] → eq[car[x];cadr[x]];
         T → apply[eval[fn;a];x;a]];
     eq[car[fn];LAMBDA] → eval[caddr[fn];parlis[cadr[fn];x;a]];
     eq[car[fn];LABEL] → apply[caddr[fn];x;cons[cons[cadr[fn];caddr[fn]];a]]]

 eval[e;a] =
    [atom[e] → cdr[assoc[e;a]];
     atom[car[e]] →
           [eq[car[e],QUOTE] → cadr[e];
            eq[car[e];COND] → evcon[cdr[e];a];
            T → apply[car[e];evlis[cdr[e];a];a]];
     T → apply[car[e];evlis[cdr[e];a];a]]

Using the function eval on an s-expression.

 eval[(EQ (QUOTE A) (CAR (CONS (QUOTE A) (QUOTE (B C D)))));NIL]