Einen einfachen Term parsen

[delimitr]

Die lexikalische Trennung der Tokens hat einen Fehler, und es kennt halt keine Datentypen und subtrahiert auch immer den linken vom rechten Operanden.
Man tippt zum Beispiel(mit Leerzeichen) ein:
x = 7 / ( 3 + 7 ) ;
und der Assemblercode kommt provisorisch raus.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

static int var_name_count=0;

void variable_countup(char *name, int do_countup)
{

 char appendix[255];
 char *base="rval";
 if ( do_countup == 1 ) ++var_name_count;
   itoa(var_name_count, appendix, 10);

 strcpy(name,base);
 strcat( name, appendix );
 return ;

}

int isnum(char c)
{
 if ( c>=0x30 && c <=0x39 ) return 1;
 return 0;

}

struct
{
 int type;
 char text[255];

}token[255];

static int num_tokens;

void remove_tokens( int position, int amount_removed )
{

 while( position+ amount_removed <= num_tokens )
 {
  token[position].type=token[position+amount_removed].type;
  strcpy( token[position].text, token[position+amount_removed].text );

  position++;
 }

 num_tokens-=amount_removed;

}

int main(void)
{
 int position;
 int txtcount;
 int left_limit, right_limit;
 int reduction_type;
 char rvalnum[20];

 position=0;

 do
 {
  txtcount=0;
  scanf("%s", token[position].text );

  if(token[position].text[0]=='+' 
     && strlen(token[position].text )== 1 ) token[position].type='+',
     txtcount++;
  else
   if(token[position].text[0]=='-'
      && strlen(token[position].text )== 1 ) token[position].type='-',
      txtcount++;
  else
   if(token[position].text[0]=='*'
      && strlen(token[position].text )== 1 ) token[position].type='*',
      txtcount++;
  else
   if(token[position].text[0]=='/'
       && strlen(token[position].text )== 1 ) token[position].type='/',
       txtcount++;
  else
   if(token[position].text[0]=='('
       && strlen(token[position].text )== 1 ) token[position].type='(',
       txtcount++;
  else
   if(token[position].text[0]==')'
      && strlen(token[position].text )== 1 ) token[position].type=')',
      txtcount++;       
  else
    if(token[position].text[0]=='='
        && strlen(token[position].text )== 1 ) token[position].type='=',
        txtcount++;
   else
    if(token[position].text[0]==';'
        && strlen(token[position].text )== 1 ) token[position].type=';',
        txtcount++;
  else
    if ( isalpha( token[position].text[0] ) )
    {
     txtcount=0;
     while( isalpha(token[position].text[txtcount] ) )txtcount++;
     while( isnum(token[position].text[txtcount] ) ) txtcount++;
     token[position].type='v'; /* Variable */
     if ( token[position].text[txtcount] != '\0' ) return 1;
    }
  else
    if ( isnum( token[position].text[0] ) )
  {
    txtcount=0;
    while( isnum( token[position].text[txtcount] ) ) txtcount++;
    token[position].type='n'; /* numerische Konstante */
    if ( token[position].text[txtcount] != '\0' ) return 1;

  }
   else { printf("Lexikalischer Fehler.\n"); getch(); return 1;}

  position++;
 }while(token[position-1].type!= ';' );
  num_tokens=position-1;

 while(reduction_type!=';' )
 {
   reduction_type=';';
  /* debug

    position=0;

    while(position < num_tokens+1 )
    {
     printf("Position: %d String: %s Typ: %c\n", position, token[position].text,
      token[position].type );
     position++;
    }
    getch();

    debug Ende  */

  left_limit=0, right_limit=num_tokens;

  position=left_limit;
  while( token[position].type!= ')'&& position < num_tokens )
  {
   position++;
  }
   if ( token[position].type== ')' )
   {
    right_limit=position;
    left_limit=position;

    while(token[left_limit].type != '(' && left_limit > 0 ) left_limit--;

    if(token[left_limit].type=='(' )
    {
     reduction_type='(';
    }
    else return 1;

   }

   position=left_limit;
   while( position+2 <= right_limit )
   {
    if ( token[position].type=='v' || token[position].type=='n'  || token[position].type=='r' )
      if ( token[position+1].type=='*' || token[position+1].type=='/' )
        if ( token[position+2].type=='v' || token[position+2].type=='n'|| token[position+2].type=='r' )
         { reduction_type=token[position+1].type;
           right_limit=position+2, left_limit=position;
           break; }
     position++;
   }
   position=left_limit;
   while( position+2 <= right_limit )
   {
    if ( token[position].type=='v' || token[position].type=='n' || token[position].type=='r' )
      if ( token[position+1].type=='+' || token[position+1].type=='-' )
        if ( token[position+2].type=='v' || token[position+2].type=='n' || token[position+2].type=='r')
         { reduction_type=token[position+1].type;
           right_limit=position+2, left_limit=position;
           break; }
     position++;
   }

   position=right_limit-2;
   while( position >=left_limit )
   {
    if ( token[position].type=='v' )
     if( token[position+1].type=='=' )
      if ( token[position+2].type== 'v' || token[position+2].type=='n' || token[position+2].type=='r')
      {
       reduction_type='=', right_limit=position+2, left_limit=position;
       break;
      }
     position--;

   }

   if ( reduction_type=='('  ) /* Klammern */
   {
     if ( right_limit-left_limit != 2 ) { printf("Fehlerhafter Klammerinhalt.\n");
           getch(); return 1; }
    if ( token[left_limit+1].type!='n' && token[left_limit+1].type!='v' &&
         token[left_limit+1].type !='r' ) { printf("Syntaxfehler bei Klammerung.\n");
          return 1; }

    variable_countup( rvalnum,1 );

    if( token[left_limit+1].type!= 'n' )
       printf("mov [%s],[%s]\n",rvalnum,token[left_limit+1].text );
    else
       printf("mov [%s],%s\n",rvalnum,token[left_limit+1].text );

    remove_tokens(left_limit,2 );

    token[left_limit].type='r';
    strcpy( token[left_limit].text, rvalnum );
   }
   else
   if ( reduction_type=='+'  ) /* Addition */
   {

    variable_countup( rvalnum,1 );

    if( token[left_limit+2].type!= 'n' )
       printf("mov ax,[%s]\n",token[left_limit+2].text );
    else
       printf("mov ax,%s\n",token[left_limit+2].text );

    if( token[left_limit].type!= 'n' )
       printf("add ax,[%s]\n",token[left_limit].text );
    else
       printf("add ax,%s\n",token[left_limit].text );

     printf("mov [%s],ax\n", rvalnum );

    remove_tokens(left_limit,2 );

    token[left_limit].type='r';
    strcpy( token[left_limit].text, rvalnum );

   }
   else
   if ( reduction_type=='-'  ) /* Subtraktion */
   {
     variable_countup( rvalnum,1 );

    if( token[left_limit+2].type!= 'n' )
       printf("mov ax,[%s]\n",token[left_limit+2].text );
    else
       printf("mov ax,%s\n",token[left_limit+2].text );

    if( token[left_limit].type!= 'n' )
       printf("sub ax,[%s]\n",token[left_limit].text );
    else
       printf("sub ax,%s\n",token[left_limit].text );

     printf("mov [%s],ax\n", rvalnum );

    remove_tokens(left_limit,2 );

    token[left_limit].type='r';
    strcpy( token[left_limit].text, rvalnum );

   }
   else
   if ( reduction_type=='*'  ) /* Multiplikation */
   {
     variable_countup( rvalnum,1 );

    if( token[left_limit+2].type!= 'n' )
       printf("mov ax,[%s]\n",token[left_limit+2].text );
    else
       printf("mov ax,%s\n",token[left_limit+2].text );

    if( token[left_limit].type!= 'n' )
       printf("mul ax,[%s]\n",token[left_limit].text );
    else
       printf("mul ax,%s\n",token[left_limit].text );

     printf("mov [%s],ax\n", rvalnum );

    remove_tokens(left_limit,2 );

    token[left_limit].type='r';
    strcpy( token[left_limit].text, rvalnum );

   }
   else
   if ( reduction_type=='/'  ) /* Division */
   {
     variable_countup( rvalnum,1 );

    if( token[left_limit].type!= 'n' )
       printf("mov ax,[%s]\n",token[left_limit].text );
    else
       printf("mov ax,%s\n",token[left_limit].text );

    if( token[left_limit+2].type!= 'n' )
       printf("div ax,[%s]\n",token[left_limit+2].text );
    else
       printf("div ax,%s\n",token[left_limit+2].text );

     printf("mov [%s],ax\n", rvalnum );

    remove_tokens(left_limit,2 );

    token[left_limit].type='r';
    strcpy( token[left_limit].text, rvalnum );

   }
   else
   if ( reduction_type== '='  ) /* Zuweisung */
   {
     variable_countup( rvalnum,1 );

     if ( token[left_limit].type=='r' ){  printf("Zuweisung zu R-Wert !\n"); return 1; }

    if( token[left_limit+2].type!= 'n' )
       printf("mov ax,[%s]\n"
              "mov [%s],ax\n",token[left_limit+2].text, token[left_limit].text );
    else
       printf("mov ax,%s\n"
              "mov [%s],ax\n",token[left_limit+2].text, token[left_limit].text );

     printf("mov [%s],ax\n", rvalnum );

    remove_tokens(left_limit,2 );

    token[left_limit].type='r';
    strcpy( token[left_limit].text, rvalnum );

   }
   else
   {
    if( num_tokens > 2 ) { printf("Operator fehlt.\n"); getch(); return 1; }
    else if ( num_tokens==2 )
       if( ( token[0].type!= 'v' && token[0].type!= 'r' &&
          token[0].type!='n') || token[1].type != ';' )
          { printf("Operator fehlt.\n"); getch(); return 1; }

    if ( num_tokens==1 && token[1].type!=';' ) { printf("Syntaxfehler.\n");
          getch(); return 1; }

   }

  }
  getch();
}

[Techel]

Wo ist jetzt die Frage?