1 files changed, 215 insertions, 0 deletions
diff --git a/expr.c b/expr.c
new file mode 100644
index 0000000..f50d42c
--- /dev/null
+++ b/expr.c
@@ -0,0 +1,215 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <ctype.h>
+#include <math.h>
+#include <string.h>
+
+#include "sheets.h"
+
+/*
+EXPR := VALUE
+| VALUE POSTFIX
+| '(' EXPR ')'
+
+VALUE := NUM
+| LOC
+
+POSTFIX := OP EXPR
+OP := '+' | '-' | '*' | '/' | '^'
+lOC := '[' NUM ',' NUM ']'
+*/
+
+#define TODO(s) fprintf(stderr, "TODO:%d: %s\n", __LINE__, s); exit(1);
+ 
+typedef struct expr expr; 
+typedef struct value value;  /* for recursive case */
+typedef struct postfix postfix;
+
+typedef enum exprType {
+	VALUE,
+	POSTFIX,	
+	NESTED,
+} exprType;
+
+typedef enum valueType {
+	NUM,
+	LOC,
+} valueType;
+
+typedef struct loc {
+        int x, y;
+} loc;
+
+typedef struct expr {
+	char *expr;
+	exprType t;
+	union {
+		expr *nested;
+		struct {
+			value *value;
+			postfix *postfix;
+		};
+	};
+} expr;
+
+typedef struct postfix {
+	char op;
+	expr *expr;
+} postfix;
+
+typedef struct value {
+	valueType t;
+	union {
+		int num;
+		loc *loc;
+	};
+} value;
+
+char isop(char c) {
+        switch (c) {
+                case '+':
+                case '-':
+                case '*':
+                case '/':
+                case '^':
+                        return c;
+        }
+        return 0;
+}
+
+char *in;
+char *Pin;
+
+void consumeleading(char c) {
+loop:
+	if (*in == c) {
+		in++;
+		goto loop;
+	}
+}
+
+expr *parseExpr(); 
+
+loc *parseLoc() {
+	consumeleading(' ');
+	loc *l = malloc(sizeof(loc));
+	if (*in == '[') {
+		int i;
+		sscanf(in, "[%d,%d]%n", &l->x, &l->y, &i);
+		if (i != 0) { 
+			in += i;
+			return l;
+		}
+		TODO("ERROR");
+	} 
+	return NULL;
+}
+
+postfix *parsePostfix() {
+	consumeleading(' ');
+	postfix *p = malloc(sizeof(postfix));
+	if (p->op = isop(*in)) {
+		in++;
+		if (p->expr = parseExpr()) 
+			return p;		
+	}
+	return NULL;
+}
+
+value *parseValue() {
+	consumeleading(' ');
+	value *v = malloc(sizeof(value));
+	if (v->loc = parseLoc()) {
+		v->t = LOC;
+		return v;
+	}
+	else if (isdigit(*in)) {
+		int i;
+		sscanf(in, "%d%n", &v->num, &i);
+		if (i != 0) {
+			in += i;
+			v->t = NUM;
+			return v;
+		}
+		TODO("ERROR");
+	} 
+	return NULL;
+}
+
+expr *parseExpr() {
+	consumeleading(' ');
+	expr *e = malloc(sizeof(expr));
+	if (e->value = parseValue()) {
+		e->t = VALUE;
+		if (e->postfix = parsePostfix())
+			e->t = POSTFIX;
+
+		return e;
+	}
+
+	else if (*in == '(') {
+		in++;
+		if (e->nested = parseExpr()) 
+			if (*in == ')')	{
+				e->t = NESTED;
+				return e;
+			}
+		TODO("ERROR");
+	}
+
+	return NULL;
+}
+
+double evalExpr(expr *e, sheet *s);
+
+double evalValue(value *v, sheet *s) {
+	if (v->t == NUM) return v->num;	
+	return evalExpr(s->cells[v->loc->y][v->loc->x], s);
+}
+
+double evalPostfix(value *v, postfix *p, sheet *s) {
+	switch (p->op) {
+		case '+': return evalValue(v, s) + evalExpr(p->expr, s);
+		case '-': return evalValue(v, s) - evalExpr(p->expr, s);
+		case '*': return evalValue(v, s) * evalExpr(p->expr, s);
+		case '/': return evalValue(v, s) / evalExpr(p->expr, s);
+		case '^': return pow(evalValue(v, s), evalExpr(p->expr, s));
+	}
+}
+
+double evalExpr(expr *e, sheet *s) {
+	switch (e->t) {  
+		case VALUE: return evalValue(e->value, s); break;
+		case POSTFIX: return evalPostfix(e->value, e->postfix, s); break;
+		case NESTED: return evalExpr(e->nested, s);
+	}
+}
+
+expr *makeNumber(int n) {
+	in = Pin;
+	memset(in, 0, 255);
+	snprintf(in, 16, "%d", n);
+	expr *e = parseExpr();
+	e->expr = strdup(Pin);
+	return e;
+}
+
+void freeValue(value *v) {
+	if (v->t == LOC) free(v->loc);
+	free(v);
+}
+
+void freePostfix(value *v, postfix *p) {
+	freeValue(v);
+	freeExpr(p->expr);
+	free(p);
+}
+
+void freeExpr(expr *e) {
+	switch (e->t) {  
+		case VALUE: freeValue(e->value); break;
+		case POSTFIX: freePostfix(e->value, e->postfix); break;
+		case NESTED: freeExpr(e->nested); break;
+	}
+	free(e);
+}