/**

 * recursive_compiler.c

 * Adapted from: http://de.wikipedia.org/wiki/Compiler

 *

 * Ein-Pass-Compiler

 */

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#define MODE_POSTFIX   0

#define MODE_ASSEMBLY  1

#define MAX           20

char lookahead;

int pos;

int compile_mode;

char expression[MAX + 1];

void error ()

{

    printf ("Syntaxfehler!\n");

}

void match (char t)

{

    if (lookahead == t) {

        lookahead = expression[++pos];

    } else

        error ();

}

void digit ()

{

    switch (lookahead) {

    case '0':

    case '1':

    case '2':

    case '3':

    case '4':

    case '5':

    case '6':

    case '7':

    case '8':

    case '9':

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

        match (lookahead);

        break;

    default:

        error ();

        break;

    }

}

void term ()

{

    digit ();

    while (1) {

        switch (lookahead) {

        case '*':

            match ('*');

            digit ();

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

            break;

        case '/':

            match ('/');

            digit ();

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

            break;

        default:

            return;

        }

    }

}

void expr ()

{

    term ();

    while (1) {

        switch (lookahead) {

        case '+':

            match ('+');

            term ();

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

            break;

        case '-':

            match ('-');

            term ();

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

            break;

        default:

            return;

        }

    }

}

int main (int argc, char **argv)

{

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

    if (fgets (expression, MAX, stdin) == NULL)

        return EXIT_FAILURE;

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

    compile_mode = MODE_POSTFIX;

    pos = 0;

    lookahead = *expression;

    expr ();

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

    compile_mode = MODE_ASSEMBLY;

    pos = 0;

    lookahead = *expression;

    expr ();

    return EXIT_SUCCESS;

}