# HG changeset patch
# User John Tsiombikas <nuclear@member.fsf.org>
# Date 1426420084 -7200
# Node ID f167a743f34820cb29fc2f2e55fbae07f809b31c
# Parent  db0630e6a97bcaed8e623c64be2c5f18ea779bb4
tutor3.txt completed minus the multi-char tokens bit

diff -r db0630e6a97b -r f167a743f348 src/main.c
--- a/src/main.c	Sun Mar 15 05:56:33 2015 +0200
+++ b/src/main.c	Sun Mar 15 13:48:04 2015 +0200
@@ -3,10 +3,20 @@
 #include <ctype.h>
 #include <stdarg.h>
 
+enum { SYM_VAR, SYM_FUNC };
+
+struct symbol {
+	int type;
+	char name;
+	struct symbol *next;
+};
+
 void init(void);
 void expression(void);
+void assignment(void);
 void term(void);
 void factor(void);
+void ident();
 void add(void);
 void sub(void);
 void mul(void);
@@ -15,16 +25,20 @@
 void match(char c);
 char get_name(void);
 char get_num(void);
+void skip_white(void);
 void stop(const char *s, ...);
 void expected(const char *s);
 void emit(const char *fmt, ...);
 void vemit(const char *fmt, va_list ap);
 void emitln(const char *fmt, ...);
 int is_addsub(char c);
+int add_symbol(char c, int type);
 
 FILE *infile, *outfile;
 char look;
 
+struct symbol *symlist;
+
 static const char *prologue =
 	"\t.globl _start\n"
 	"_start:\n"
@@ -46,16 +60,30 @@
 	/* output prologue */
 	fputs(prologue, outfile);
 
-	expression();
+	assignment();
+	if(look != '\n') {
+		expected("newline");
+	}
 
 	/* output epilogue */
 	fputs(epilogue, outfile);
+	/* write all variable declarations */
+	fprintf(outfile, "\t.data\n");
+	while(symlist) {
+		struct symbol *sym = symlist;
+		symlist = symlist->next;
+		if(sym->type == SYM_VAR) {
+			fprintf(outfile, "%c:\t.long 0\n", sym->name);
+		}
+		free(sym);
+	}
 	return 0;
 }
 
 void init(void)
 {
 	get_char();
+	skip_white();
 }
 
 void expression(void)
@@ -75,12 +103,23 @@
 		case '-':
 			sub();
 			break;
-		default:
-			expected("addop");
 		}
 	}
 }
 
+void assignment(void)
+{
+	char name = get_name();
+	match('=');
+
+	if(add_symbol(name, SYM_VAR) == -1) {
+		stop("variable name '%c' previously defined as another type of symbol\n", name);
+	}
+
+	expression();
+	emitln("mov %%eax, (%c)", name);
+}
+
 void term(void)
 {
 	factor();
@@ -93,8 +132,6 @@
 		case '/':
 			divide();
 			break;
-		default:
-			expected("mulop");
 		}
 	}
 }
@@ -105,11 +142,34 @@
 		match('(');
 		expression();
 		match(')');
+	} else if(isalpha(look)) {
+		ident();
 	} else {
 		emitln("mov $%c, %%eax", get_num());
 	}
 }
 
+void ident()
+{
+	char name = get_name();
+	if(look == '(') {
+		/* function call */
+		match('(');
+		match(')');
+
+		if(add_symbol(name, SYM_FUNC) == -1) {
+			stop("function name '%c' previously defined as another type of symbol\n", name);
+		}
+		emitln("call %c", name);
+	} else {
+		/* variable */
+		if(add_symbol(name, SYM_VAR) == -1) {
+			stop("variable name '%c' previously defined as another type of symbol\n", name);
+		}
+		emitln("mov (%c), %%eax", name);
+	}
+}
+
 void add(void)
 {
 	match('+');
@@ -153,6 +213,7 @@
 {
 	if(look == c) {
 		get_char();
+		skip_white();
 	} else {
 		char s[2] = {0, 0};
 		s[0] = c;
@@ -168,6 +229,7 @@
 	}
 	res = toupper(look);
 	get_char();
+	skip_white();
 	return res;
 }
 
@@ -179,9 +241,17 @@
 	}
 	res = look;
 	get_char();
+	skip_white();
 	return res;
 }
 
+void skip_white(void)
+{
+	while(isblank(look)) {
+		get_char();
+	}
+}
+
 void stop(const char *s, ...)
 {
 	va_list ap;
@@ -228,3 +298,25 @@
 {
 	return c == '+' || c == '-';
 }
+
+int add_symbol(char c, int type)
+{
+	struct symbol *sym = symlist;
+	while(sym) {
+		if(sym->name == c) {
+			/* we already have it */
+			return sym->type == type ? 0 : -1;
+		}
+		sym = sym->next;
+	}
+
+	if(!(sym = malloc(sizeof *sym))) {
+		perror("ICE: failed to allocate memory");
+		abort();
+	}
+	sym->name = c;
+	sym->type = type;
+	sym->next = symlist;
+	symlist = sym;
+	return 0;
+}