nuclear@0: #include <stdio.h>
nuclear@0: #include <stdlib.h>
nuclear@0: #include <ctype.h>
nuclear@0: #include <stdarg.h>
nuclear@0: 
nuclear@0: void init(void);
nuclear@0: void expression(void);
nuclear@0: void term(void);
nuclear@0: void factor(void);
nuclear@0: void add(void);
nuclear@0: void sub(void);
nuclear@0: void mul(void);
nuclear@0: void divide(void);
nuclear@0: void get_char(void);
nuclear@0: void match(char c);
nuclear@0: char get_name(void);
nuclear@0: char get_num(void);
nuclear@0: void stop(const char *s, ...);
nuclear@0: void expected(const char *s);
nuclear@0: void emit(const char *fmt, ...);
nuclear@0: void vemit(const char *fmt, va_list ap);
nuclear@0: void emitln(const char *fmt, ...);
nuclear@0: int is_addsub(char c);
nuclear@0: 
nuclear@0: FILE *infile, *outfile;
nuclear@0: char look;
nuclear@0: 
nuclear@0: static const char *prologue =
nuclear@0: 	"\t.globl _start\n"
nuclear@0: 	"_start:\n"
nuclear@0: 	"\tcall main\n"
nuclear@0: 	"\tmov %eax, %ebx\n"
nuclear@0: 	"\tmov $1, %eax\n"
nuclear@0: 	"\tint $0x80\n"
nuclear@0: 	"main:\n"
nuclear@0: 	"\t# ---- START ----\n";
nuclear@0: 
nuclear@0: static const char *epilogue = "\t# ---- END ----\n\tret\n";
nuclear@0: 
nuclear@0: int main(void)
nuclear@0: {
nuclear@0: 	infile = stdin;
nuclear@0: 	outfile = stdout;
nuclear@0: 
nuclear@0: 	init();
nuclear@0: 	/* output prologue */
nuclear@0: 	fputs(prologue, outfile);
nuclear@0: 
nuclear@0: 	expression();
nuclear@0: 
nuclear@0: 	/* output epilogue */
nuclear@0: 	fputs(epilogue, outfile);
nuclear@0: 	return 0;
nuclear@0: }
nuclear@0: 
nuclear@0: void init(void)
nuclear@0: {
nuclear@0: 	get_char();
nuclear@0: }
nuclear@0: 
nuclear@0: void expression(void)
nuclear@0: {
nuclear@0: 	if(is_addsub(look)) {
nuclear@0: 		emitln("xor %%eax, %%eax");
nuclear@0: 	} else {
nuclear@0: 		term();
nuclear@0: 	}
nuclear@0: 
nuclear@0: 	while(is_addsub(look)) {
nuclear@0: 		emitln("push %%eax");
nuclear@0: 		switch(look) {
nuclear@0: 		case '+':
nuclear@0: 			add();
nuclear@0: 			break;
nuclear@0: 		case '-':
nuclear@0: 			sub();
nuclear@0: 			break;
nuclear@0: 		default:
nuclear@0: 			expected("addop");
nuclear@0: 		}
nuclear@0: 	}
nuclear@0: }
nuclear@0: 
nuclear@0: void term(void)
nuclear@0: {
nuclear@0: 	factor();
nuclear@0: 	while(look == '*' || look == '/') {
nuclear@0: 		emitln("push %%eax");
nuclear@0: 		switch(look) {
nuclear@0: 		case '*':
nuclear@0: 			mul();
nuclear@0: 			break;
nuclear@0: 		case '/':
nuclear@0: 			divide();
nuclear@0: 			break;
nuclear@0: 		default:
nuclear@0: 			expected("mulop");
nuclear@0: 		}
nuclear@0: 	}
nuclear@0: }
nuclear@0: 
nuclear@0: void factor(void)
nuclear@0: {
nuclear@0: 	if(look == '(') {
nuclear@0: 		match('(');
nuclear@0: 		expression();
nuclear@0: 		match(')');
nuclear@0: 	} else {
nuclear@0: 		emitln("mov $%c, %%eax", get_num());
nuclear@0: 	}
nuclear@0: }
nuclear@0: 
nuclear@0: void add(void)
nuclear@0: {
nuclear@0: 	match('+');
nuclear@0: 	term();
nuclear@0: 	emitln("pop %%ebx");
nuclear@0: 	emitln("add %%ebx, %%eax");
nuclear@0: }
nuclear@0: 
nuclear@0: void sub(void)
nuclear@0: {
nuclear@0: 	match('-');
nuclear@0: 	term();
nuclear@0: 	emitln("pop %%ebx");
nuclear@0: 	emitln("sub %%ebx, %%eax");
nuclear@0: 	emitln("neg %%eax");
nuclear@0: }
nuclear@0: 
nuclear@0: void mul(void)
nuclear@0: {
nuclear@0: 	match('*');
nuclear@0: 	factor();
nuclear@0: 	emitln("pop %%ebx");
nuclear@0: 	emitln("imul %%ebx");
nuclear@0: }
nuclear@0: 
nuclear@0: void divide(void)
nuclear@0: {
nuclear@0: 	match('/');
nuclear@0: 	factor();
nuclear@0: 	emitln("mov %%eax, %%ebx");
nuclear@0: 	emitln("pop %%eax");
nuclear@0: 	emitln("idiv %%ebx");
nuclear@0: }
nuclear@0: 
nuclear@0: void get_char(void)
nuclear@0: {
nuclear@0: 	look = fgetc(infile);
nuclear@0: }
nuclear@0: 
nuclear@0: void match(char c)
nuclear@0: {
nuclear@0: 	if(look == c) {
nuclear@0: 		get_char();
nuclear@0: 	} else {
nuclear@0: 		char s[2] = {0, 0};
nuclear@0: 		s[0] = c;
nuclear@0: 		expected(s);
nuclear@0: 	}
nuclear@0: }
nuclear@0: 
nuclear@0: char get_name(void)
nuclear@0: {
nuclear@0: 	char res;
nuclear@0: 	if(!isalpha(look)) {
nuclear@0: 		expected("name");
nuclear@0: 	}
nuclear@0: 	res = toupper(look);
nuclear@0: 	get_char();
nuclear@0: 	return res;
nuclear@0: }
nuclear@0: 
nuclear@0: char get_num(void)
nuclear@0: {
nuclear@0: 	char res;
nuclear@0: 	if(!isdigit(look)) {
nuclear@0: 		expected("integer");
nuclear@0: 	}
nuclear@0: 	res = look;
nuclear@0: 	get_char();
nuclear@0: 	return res;
nuclear@0: }
nuclear@0: 
nuclear@0: void stop(const char *s, ...)
nuclear@0: {
nuclear@0: 	va_list ap;
nuclear@0: 
nuclear@0: 	fprintf(stderr, "error: ");
nuclear@0: 	va_start(ap, s);
nuclear@0: 	vfprintf(stderr, s, ap);
nuclear@0: 	va_end(ap);
nuclear@0: 	fputc('\n', stderr);
nuclear@0: 
nuclear@0: 	abort();
nuclear@0: }
nuclear@0: 
nuclear@0: void expected(const char *s)
nuclear@0: {
nuclear@0: 	stop("%s expected", s);
nuclear@0: }
nuclear@0: 
nuclear@0: void emit(const char *fmt, ...)
nuclear@0: {
nuclear@0: 	va_list ap;
nuclear@0: 	va_start(ap, fmt);
nuclear@0: 	vemit(fmt, ap);
nuclear@0: 	va_end(ap);
nuclear@0: }
nuclear@0: 
nuclear@0: void vemit(const char *fmt, va_list ap)
nuclear@0: {
nuclear@0: 	fputc('\t', outfile);
nuclear@0: 	vfprintf(outfile, fmt, ap);
nuclear@0: }
nuclear@0: 
nuclear@0: void emitln(const char *fmt, ...)
nuclear@0: {
nuclear@0: 	va_list ap;
nuclear@0: 	va_start(ap, fmt);
nuclear@0: 	vemit(fmt, ap);
nuclear@0: 	va_end(ap);
nuclear@0: 	fputc('\n', outfile);
nuclear@0: }
nuclear@0: 
nuclear@0: 
nuclear@0: int is_addsub(char c)
nuclear@0: {
nuclear@0: 	return c == '+' || c == '-';
nuclear@0: }