Брайан Керниган - UNIX — универсальная среда программирования

extern prexpr();

extern gt(), lt(), eq(), ge(), le(), ne(), and(), or(), not();

extern ifcode(), whilecode();

%{

#include "hoc.h"

#define code2(c1,c2) code(c1); code(c2)

#define code3(c1,c2,c3) code(c1); code(c2); code(c3)

%}

%union {

Symbol *sym; /* symbol table pointer */

Inst *inst; /* machine instruction */

}

%token NUMBER PRINT VAR BLTIN UNDEF WHILE IF ELSE

%type stmt asgn expr stmtlist cond while if end

%right '='

%left OR

%left AND

%left GT GE LT LE EQ NE

%left '+' '-'

%left '*' '/'

%left UNARYMINUS NOT

%right

%%

list: /* nothing */

| list '\n'

| list asgn '\n' { code2(pop, STOP); return 1; }

| list stmt '\n' { code(STOP); return 1; }

| list expr '\n' { code2(print, STOP); return 1; }

| list error '\n' { yyerrok; }

;

asgn: VAR '=' expr { $$=$3; code3(varpush,(Inst)$1.assign); }

;

stmt: expr { code(pop); }

| PRINT expr { code(prexpr); $$ = $2; }

| while cond stmt end {

($1)[1] = (Inst)$3; /* body of loop */

($1)[2] = (Inst)$4;

} /* end, if cond fails */

| if cond stmt end { /* else-less if */

($1)[1] = (Inst)$3; /* thenpart */

($1)[2] = (Inst)$4;

} /* end, if cond fails */

| if cond stmt end ELSE stmt end { /* if with else */

($1)[1] = (Inst)$3; /* thenpart */

($1)[2] = (Inst)$6; /* elsepart */

($1)[3] = (Inst)$7;

} /* end, if cond fails */

| '{' stmtlist '}' { $$ = $2; }

;

cond: '(' expr ')' { code(STOP); $$ = $2; }

;

while: WHILE { $$ = code3(whilecode, STOP, STOP); }

;

if: IF { $$=code(ifcode); code3(STOP, STOP, STOP); }

;

end: /* nothing */ { code(STOP); $$ = progp; }

;

stmtlist: /* nothing */ { $$ = progp; }

| stmtlist '\n'

| stmtlist stmt

;

expr: NUMBER { $$ = code2(constpush, (Inst)$1); }

| VAR { $$ = code3(varpush, (Inst)$1, eval); }

| asgn

| BLTIN '(' expr ')'

{ $$ = $3; code2(bltin,(Inst)$1->u.ptr); }

| '(' expr ')' { $$ = $2; }

| expr '+' expr { code(add); }

| expr '-' expr { code(sub); }

| expr '*' expr { code(mul); }

| expr '/' expr { code(div); }

| expr '^' expr { code (power); }

| '-' expr %prec UNARYMINUS { $$ = $2; code(negate); }

| expr GT expr { code(gt); }

| expr GE expr { code(ge); }

| expr LT expr { code(lt); }

| expr LE expr { code(le); }

| expr EQ expr { code(eq); }

| expr NE expr { code(ne); }

| expr AND expr { code(and); }

| expr OR expr { code(or); }

| NOT expr { $$ = $2; code(not); }

;

%%

/* end of grammar */

#include

#include

char *progname;

int lineno = 1;

#include

#include

jmp_buf begin;

int defining;

int c; /* global for use by warning() */

yylex() /* hoc5 */

{

while ((c=getchar()) == ' ' || c == '\t')

;

if (c == EOF)

return 0;

if (c == '.' || isdigit(c)) { /* number */

double d;

ungetc(c, stdin);

scanf("%lf", &d);

yylval.sym = install("", NUMBER, d);

return NUMBER;

}

if (isalpha(c)) {

Symbol *s;

char sbuf[100], *p = sbuf;

do

*p++ = c;

while ((c=getchar()) != EOF && isalnum(c));

ungetc(c, stdin);

*p = '\0';

if ((s=lookup(sbuf)) == 0)

s = install(sbuf, UNDEF, 0.0);

yylval.sym = s;

return s->type == UNDEF ? VAR : s->type;

}

switch (c) {

case '>': return follow('=', GE, GT);

case '<': return follow('=', LE, LT);

case '=': return follow('=', EQ, '=');

case '!': return follow('=', NE, NOT);

case '|': return follow('|', OR, '|');

case '&': return follow('&', AND, '&');

case '\n': lineno++; return '\n';

default: return c;

}

}

follow(expect, ifyes, ifno) /* look ahead for >=, etc. */

{

int c = getchar();

if (c == expect)

return ifyes;

ungetc(c, stdin);

return ifno;

}

yyerror(s)

char *s;

{

warning(s, (char*)0);

}

execerror(s, t) /* recover from run-time error */

char *s, *t;

{

warning(s, t);

longjmp(begin, 0);

}

fpecatch() /* catch floating point exceptions */

{

execerror("floating point exception", (char*)0);

}

main(argc, argv)

char *argv[];

{

int fpecatch();

progname = argv[0];

init();

setjmp(begin);

signal(SIGFPE, fpecatch);

for (initcode(); yyparse(); initcode())

execute(prog);

return 0;

}

warning(s, t)

char *s, *t;

{

fprintf(stderr, "%s: %s", progname, s);

if (t && *t)

fprintf(stderr, " %s", t);

fprintf(stderr, " near line %d\n", lineno);

while (c != '\n' && с != EOF)

c = getchar(); /* flush rest of input line */

fseek(stdin, 0L, 2); /* flush rest of file */

longjmp(begin, 0);

}

#include "hoc.h"

#include "y.tab.h"

#include

extern double Log(), Log10(), Sqrt(), Exp(), integer();

static struct { /* Keywords */

char *name;

int kval;

} keywords[] = {

"if", IF,

"else", ELSE,

"while", WHILE,