new reader

1 files changed, 98 insertions, 0 deletions

diff --git a/read.c b/read.c
new file mode 100644
index 0000000..047dfb9
--- /dev/null
+++ b/read.c
@@ -0,0 +1,98 @@
+#include "val.h"
+#include "util.h"
+
+#include <string.h>
+
+typedef struct _reader {
+	char *c;
+	State *S;
+} Reader;
+
+
+static void next(Reader *R) { CHECK(*R->c != '\0',"end of string reached"); R->c++; }
+static bool is_ws(char x) {	return x == ' ' || x == '\t' || x == '\n';}
+static bool is_num(char x) { return '0' <= x && x <= '9'; }
+static bool is_special(char x) {
+	switch(x) {
+	case '(': case ')': case '[': case ']': case '\'': case '"':
+	return true; break;
+	default: return false; break;
+	}
+}
+static bool is_normal(char x) {
+	return !(is_ws(x) || is_special(x));
+}
+static void skipws(Reader *R) {	while (is_ws(*R->c)) next(R); }
+
+static Val symbol(Reader *R);
+static Val string(Reader *R);
+static Val list(Reader *R, char closer);
+
+#define STR(S, s) (VAL_OBJ(objstring_copy_cstr(S, s)))
+
+static Val expr(Reader *R) {
+	skipws(R);
+	switch (*R->c) {
+	case '"':
+		next(R); return string(R);
+		break;
+	case '(':
+		next(R); return list(R, ')');
+		break;
+	case '[':
+		next(R); 
+		ObjArr *a = AS_ARR(list(R, ']'));
+		objarr_insert(R->S, a, 0, STR(R->S, "arr"));
+		return VAL_OBJ(a);
+		break;
+	default: return symbol(R); break;
+	}
+}
+static Val symbol(Reader *R) {
+	char *start = R->c;
+	int len = 0;
+	bool num = true;
+	while (is_normal(*R->c)) { num &= is_num(*R->c); len += 1; next(R); }
+	if (num) {
+		// c moment
+		char *tmp = malloc(len+1);
+		memcpy(tmp, start, len);
+		tmp[len] = 0;
+		int x = atoi(tmp);
+		free(tmp);
+		return VAL_NUM((double)x);
+	} else {
+		ObjString *o = objstring_copy(R->S, start, len);
+		return VAL_OBJ(o);
+	}
+}
+static Val string(Reader *R) {
+	char *start = R->c;
+	int len = 0;
+	// todo, escape sequences
+	while (*R->c != '"') { len += 1; next(R); }
+	next(R);
+	ObjString *s = objstring_copy(R->S, start, len);
+	ObjArr *a = objarr_new(R->S);
+	objarr_append(R->S, a, STR(R->S, "quote"));
+	objarr_append(R->S, a, VAL_OBJ(s));
+	return VAL_OBJ(a);
+}
+static Val list(Reader *R, char closer) {
+	ObjArr *a = objarr_new(R->S);
+	while (true) {
+		skipws(R);
+		if (*R->c == closer) {
+			next(R);
+			return VAL_OBJ(a);
+		}
+		objarr_append(R->S, a, expr(R));
+	}
+}
+
+
+Val read_expr(State *S, char *str) {
+	Reader r = (Reader){.S=S, .c=str};
+	return expr(&r);
+}
+