UNIX — универсальная среда программирования

Керниган Брайан Уилсон

 d = pop;

 printf("\t%.8g\n", d.val);

}

prexpr /* print numeric value */

{

 Datum d;

 d = pop;

 printf("%.8g\n", d.val);

}

Inst *code(f) /* install one instruction or operand */

 Inst f;

{

 Inst *oprogp = progp;

 if (progp >= &prog[NPROG])

execerror("expression too complicated", (char*)0);

 *progp++ = f;

 return oprogp;

}

execute(p)

 Inst *p;

{

 for (pc = p; *pc != STOP; ) (*(*pc++));

}

3.6.2

fib

{

 a=0

 b=1

 while(b<1000) {

c=b

b=a+b

a=c

print(c)

 }

}

3.6.3

fib2

{

 n=0

 a=0

 b=1

 while(b<10000000){

n=n+1

c=b

b=a+b

a=c

print(b)

 }

 print(n)

}

3.6.4

hoc.h

typedef struct Symbol { /* symbol table entry */

 char *name;

 short type; /* VAR, BLTIN, UNDEF */

 union {

double val; /* if VAR */

double (*ptr); /* if BLTIN */

 } u;

 struct Symbol *next; /* to link to another */

} Symbol;

Symbol *install, *lookup;

typedef union Datum { /* interpreter stack type */

 double val;

 Symbol *sym;

} Datum;

extern Datum pop;

typedef int (*Inst); /* machine instruction */

#define STOP (Inst)0

extern Inst prog[], *progp, *code;

extern eval, add, sub, mul, div, negate, power;

extern assign, bltin, varpush, constpush, print;

extern prexpr;

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

extern ifcode, whilecode;

3.6.5

hoc.y

%{

#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 <sym> NUMBER PRINT VAR BLTIN UNDEF WHILE IF ELSE

%type <inst> 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; }

 ;