machop.c

简单的编译词法分析 in c

/*
  machop.c

  We have to implement four operations to machine:

  CONNECTION:

             -----------       -----------
       ----> |   m1    | ----> |   m2    |
             -----------       -----------

  UNION:

                   --------
         epsilon  /|  m1  |\
                /  --------  \
         ---->[S]             [Z]---->
                \            /
	          \--------/
                   |  m2  |
                   --------
   STAR:
                    ----------
                    |        |
                    v        |
              -----------    |
        ----->|    m1   |-----
              -----------


   SUB-MACHINE:

                  'ch'
       ----->[S]-------->[Z]------>
  
 */

#include "machop.h"
#include<stdio.h>
#define STKSIZ 10
Mach mstk[STKSIZ];
int msp = 0;
#undef STKSIZ

#define PUSH(m) (mstk[msp++] = m)
#define POP() (mstk[--msp])
#define EMPTY() (msp == 0)
#define PEEK() (mstk[msp-1])

#define EP '$'

void conn()
{
  Mach m1, m2, m3;


  m2 = POP();
  m1 = POP();

  addtran(m1.t, m2.h, EP);

  m3.h = m1.h; 
  m3.t = m2.t;

  PUSH(m3);
}

void uni()
{
  Mach m1, m2, m3;
  stat s, z;

  m2 = POP();
  m1 = POP();

  s = new_st();
  z = new_st();

  addtran(s, m1.h, EP);
  addtran(s, m2.h, EP);
  addtran(m1.t, z, EP);
  addtran(m2.t, z, EP);

  m3.h = s;
  m3.t = z;

  PUSH(m3);
}

void star()
{
  Mach m1;

  m1 = PEEK();

  addtran(m1.t, m1.h, EP);
  addtran(m1.h, m1.t, EP);
}

void subm(char ch)
{
  Mach m1;
  stat s, z;

  s = new_st();
  z = new_st();

  addtran(s, z, ch);

  m1.h = s;
  m1.t = z;
  
  PUSH(m1);
}

void finalm()
{
  finm = PEEK();
  printf("\nstart state: %d\nfinal state: %d\n", 
	 finm.h, finm.t);
}

#undef PUSH
#undef POP
#undef EMPTY
#undef PEEK

extern char expr[];
extern int elen;

void genm()
{ int i;
  puts("\nLevel3:\n\t");
 
  for (i=0; i<elen; i++) {
    char ch = expr[i];
    switch (ch) {
    case '.':
      conn();
      break;
    case '|':
      uni();
      break;
    case '*':
      star();
      break;
    default:
      subm(ch);
      break;
    }
  }
  finalm();
}