UNIX — универсальная среда программирования - Керниган Брайан Уилсон

}

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; }