Created
January 21, 2022 18:33
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%{ | |
#include <stdio.h> | |
#include <stdlib.h> | |
#include <string.h> | |
#include <ctype.h> | |
extern int yylex(void); | |
int yyerror(const char *s) { printf("%s\n", s); return 0; } | |
int node[4096]; int nnum = 1; | |
int car[2048], cdr[2048]; int cnum = 1; | |
char symbol[2048][32]; int snum = 1; | |
int cons(int a, int d) { | |
car[cnum] = a; cdr[cnum] = d; | |
node[nnum] = cnum; cnum++; nnum++; | |
return nnum - 1; | |
} | |
int head(int s) { return car[node[s]]; } | |
int tail(int s) { return cdr[node[s]]; } | |
int lref(int s, int num) { | |
return num == 0 ? head(s) : lref(tail(s), num - 1); | |
} | |
int setsym(char *str) { | |
strcpy(symbol[snum], str); node[nnum] = -snum; | |
snum++; nnum++; return nnum - 1; | |
} | |
const char *getsym(int s) { return symbol[-node[s]]; } | |
#define N 0 | |
#define T 1 | |
#define F 0 | |
int pairp(int s) { return node[s] > 0 ? T : F; } | |
int nullp(int s) { return s == N ? T : F; } | |
int eqsymp(int x, const char *y) { return !strcmp(getsym(x), y); } | |
int intp(int s) { | |
const char *str = getsym(s); int i; | |
for (i = 0; i < strlen(str); i++) | |
if (!isdigit(str[i]) && str[i] != '-') break; | |
return i == strlen(str) ? T : F; | |
} | |
void sw(int s) { | |
if (pairp(s)) { | |
printf("("); sw(head(s)); | |
if (pairp(tail(s))) | |
for (int n = tail(s); !nullp(n); n = tail(n)) { | |
printf(" "); sw(head(n)); | |
} | |
else if (tail(s) != N) { printf(" . "); sw(tail(s)); } | |
printf(")"); | |
} else printf("%s", getsym(s)); | |
} | |
int ap(int x, int y) { | |
if (nullp(x)) return y; else cons(head(x), ap(tail(x), y)); | |
} | |
int pm(int k, int v) { | |
if (nullp(k) || nullp(v)) return N; | |
else cons(head(k), cons(head(v), pm(tail(k), tail(v)))); | |
} | |
int pq(int k, int pl) { | |
if (nullp(pl)) return F; | |
else if (eqsymp(k, getsym(head(pl)))) return lref(pl, 1); | |
else return pq(k, tail(tail(pl))); | |
} | |
int sq(int s, int e) { | |
if (eqsymp(s, "+") || eqsymp(s, "-") || eqsymp(s, "eq?") || | |
eqsymp(s, "cons") || eqsymp(s, "car") || eqsymp(s, "cdr")) | |
return s; | |
else return pq(s, e); | |
} | |
enum OP { ADD, SUB }; | |
int op(enum OP f, int a) { | |
int a1 = atoi(getsym(head(a))), a2 = atoi(getsym(head(tail(a)))), r; | |
switch (f) { | |
case ADD: r = a1 + a2; break; | |
case SUB: r = a1 - a2; break; | |
} | |
char str[32]; sprintf(str, "%d", r); return setsym(str); | |
} | |
int ay(int f, int a) { | |
if (eqsymp(f, "+")) return op(ADD, a); | |
else if (eqsymp(f, "-")) return op(SUB, a); | |
else if (eqsymp(f, "cons")) return cons(lref(a, 0), lref(a, 1)); | |
else if (eqsymp(f, "car")) return head(lref(a, 0)); | |
else if (eqsymp(f, "cdr")) return tail(lref(a, 0)); | |
else if (eqsymp(f, "eq?")) { | |
int a1 = lref(a, 0), a2 = lref(a, 1); | |
if (nullp(a1) && nullp(a2)) return T; | |
else if (nullp(a1) || nullp(a2)) return F; | |
else return eqsymp(a1, getsym(a2)); | |
} | |
} | |
int ev(int s, int e); | |
int ea(int a, int e) { | |
return nullp(a) ? N : cons(ev(head(a), e), ea(tail(a), e)); | |
} | |
int ev(int s, int e) { | |
if (pairp(s)) { | |
int h = head(s); | |
if (!pairp(h) && (eqsymp(h, "quote"))) return head(tail(s)); | |
else if (!pairp(h) && (eqsymp(h, "if"))) | |
return ev(lref(s, 1), e) ? ev(lref(s, 2), e) : ev(lref(s, 3), e); | |
else if (!pairp(h) && (eqsymp(h, "lambda"))) return ap(s, cons(e, N)); | |
else { | |
int f = ev(h, e), a = ea(tail(s), e); | |
if (!pairp(f)) return ay(f, a); | |
else return ev(lref(f, 2), ap(pm(lref(f, 1), a), lref(f, 3))); | |
} | |
} else return intp(s) ? s : sq(s, e); | |
} | |
%} | |
%defines | |
%union { char *symbol; int node; } | |
%token EMPTY DOT | |
%token <symbol> SYMBOL | |
%type <node> s list | |
%% | |
in : s { sw(ev(nnum - 1, N)); printf("\n"); return 0; } | |
; | |
s : EMPTY { $$ = N; } | |
| SYMBOL { $$ = setsym($1); } | |
| '(' list ')' { $$ = $2; } | |
; | |
list : s { $$ = cons($1, N); } | |
| s list { $$ = cons($1, $2); } | |
| s DOT s { $$ = cons($1, $3); } | |
; | |
%% | |
#include "lex.yy.c" | |
int main(void) { yyparse(); return 0; } |
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