1 /**

     2  * Ein-Pass-Compiler

     3  *

     4  */

     5 

     6 #include <stdlib.h>

     7 #include <stdio.h>

     8 #include <string.h>

     9 

    10 #define MODE_POSTFIX   0

    11 #define MODE_ASSEMBLY  1

    12 

    13 char lookahead;

    14 int pos;

    15 int compile_mode;

    16 char expression[20 + 1];

    17 

    18 void error ()

    19 {

    20     printf ("Syntaxfehler!\n");

    21 }

    22 

    23 void match (char t)

    24 {

    25     if (lookahead == t) {

    26         lookahead = expression[++pos];

    27     } else

    28         error ();

    29 }

    30 

    31 void digit ()

    32 {

    33     switch (lookahead) {

    34     case '0':

    35     case '1':

    36     case '2':

    37     case '3':

    38     case '4':

    39     case '5':

    40     case '6':

    41     case '7':

    42     case '8':

    43     case '9':

    44         printf (compile_mode == MODE_POSTFIX ? "%c" : "\tPUSH %c\n", lookahead);

    45         match (lookahead);

    46         break;

    47     default:

    48         error ();

    49         break;

    50     }

    51 }

    52 

    53 void term ()

    54 {

    55     digit ();

    56     while (1) {

    57         switch (lookahead) {

    58         case '*':

    59             match ('*');

    60             digit ();

    61             printf ("%s", compile_mode == MODE_POSTFIX ? "*" : "\tPOP B\n\tPOP A\n\tMUL A, B\n\tPUSH A\n");

    62             break;

    63         case '/':

    64             match ('/');

    65             digit ();

    66             printf ("%s", compile_mode == MODE_POSTFIX ? "/" : "\tPOP B\n\tPOP A\n\tDIV A, B\n\tPUSH A\n");

    67             break;

    68         default:

    69             return;

    70         }

    71     }

    72 }

    73 

    74 void expr ()

    75 {

    76     term ();

    77     while (1) {

    78         switch (lookahead) {

    79         case '+':

    80             match ('+');

    81             term ();

    82             printf ("%s", compile_mode == MODE_POSTFIX ? "+" : "\tPOP B\n\tPOP A\n\tADD A, B\n\tPUSH A\n");

    83             break;

    84         case '-':

    85             match ('-');

    86             term ();

    87             printf ("%s", compile_mode == MODE_POSTFIX ? "-" : "\tPOP B\n\tPOP A\n\tSUB A, B\n\tPUSH A\n");

    88             break;

    89         default:

    90             return;

    91         }

    92     }

    93 }

    94 

    95 int main (int argc, char **argv)

    96 {

    97     printf ("Bitte geben Sie einen Ausdruck in Infix-Notation ein:\n\n\t");

    98     fgets (expression, 20, stdin);

    99 

   100     printf ("\nCompilierter Ausdruck in Postfix-Notation:\n\n\t");

   101     compile_mode = MODE_POSTFIX;

   102     pos = 0;

   103     lookahead = *expression;

   104     expr ();

   105 

   106     printf ("\n\nCompilierter Ausdruck in Assemblersprache:\n\n");

   107     compile_mode = MODE_ASSEMBLY;

   108     pos = 0;

   109     lookahead = *expression;

   110     expr ();

   111 

   112     return 0;

   113 }