more code

1 files changed, 126 insertions, 0 deletions

diff --git a/run.c b/run.c
new file mode 100644
index 0000000..eb65400
--- /dev/null
+++ b/run.c
@@ -0,0 +1,126 @@
+#include "run.h"
+#include "ast.h"
+
+#include <stdio.h>
+#include <string.h>
+
+// static int valueof(AstNode *a) {
+// 	if (a->ty != AST_NUM) {
+// 		printf("i need a number\n");
+// 		return -1;
+// 	} else {
+// 		return a->as.num;
+// 	}
+// }
+
+// void run_thing(AstNode *a) {
+// 	if (a->ty != AST_LIST) 
+// 		printf("can only run a list\n");
+// 	else if (a->as.list.len < 3)
+// 		printf("need at least 3 elements\n");
+// 	else {
+// 		AstNode *fn = &a->as.list.vals[0];
+// 		if (fn->ty != AST_SYMBOL) 
+// 			printf("first el needs to be symbol\n");
+// 		else if (strcmp(fn->as.str, "+"))
+// 			printf("can only run +\n");
+// 		else {
+// 			int v1 = valueof(&a->as.list.vals[1]);
+// 			int v2 = valueof(&a->as.list.vals[2]);
+// 			printf("=> %d\n",v1+v2);
+// 		}
+// 	}
+// }
+
+int eval (AstNode a);
+
+// return pointer to nth subnode of AST_LIST node *l.
+// doesn't check that l is a list, or that it has at least n elems. 
+#define NTH(l,n) (&(l)->as.list.vals[(n)])
+
+// n is max index
+#define CK_LEN(s, l, n) do { if(l.len-1 != n) { \
+	printf("%s fn requires exactly %d args (%ld provided)",\
+	s, n, l.len-1); return 0; } } while(0);
+static int func_plus(AstVec l) {
+	CK_LEN("+",l,2);
+	return eval(l.vals[1]) + eval(l.vals[2]);
+}
+static int func_id(AstVec l) {
+	CK_LEN("id",l,1);
+	return eval(l.vals[1]);
+}
+static int func_minus(AstVec l) {
+	CK_LEN("-",l,2);
+	return eval(l.vals[1]) - eval(l.vals[2]);
+}
+static int func_mult(AstVec l) {
+	CK_LEN("*",l,2);
+	return eval(l.vals[1]) * eval(l.vals[2]);
+}
+static int func_div(AstVec l) {
+	CK_LEN("/",l,2);
+	return eval(l.vals[1]) / eval(l.vals[2]);
+}
+static int func_print(AstVec l) {
+	CK_LEN("print",l,1);
+	int v = eval(l.vals[1]);
+	printf("%d\n",v);
+	return v;
+}
+
+typedef int (*builtin_func)(AstVec);
+typedef struct {
+	char *name;
+	builtin_func func;
+} BuiltinDesc;
+
+BuiltinDesc builtins[] = {
+	{ "+", func_plus },
+	{ "-", func_minus },
+	{ "*", func_mult },
+	{ "/", func_div },
+	{ "id", func_id },
+	{ "print", func_print },
+	{ NULL, NULL },
+};
+
+static int call_builtin(char *name, AstVec arglist) {
+	for (BuiltinDesc *bd = builtins; bd->name != NULL; bd++) {
+		if (0 == strcmp(bd->name, name)) {
+			return bd->func(arglist);
+		}
+	}
+	printf("couldn't find builtin fn %s\n",name);
+	return 0;
+}
+
+
+int eval(AstNode a) {
+	switch (a.ty) {
+	case AST_SYMBOL:
+		printf("cant yet read variable [%s]\n", a.as.str);
+		return 0;
+		break;
+	case AST_NUM:
+		return a.as.num;
+		break;
+	case AST_LIST:;
+		AstVec l = a.as.list;
+		if (l.len < 1) {
+			printf("can't execute empty list\n");
+			return 0;
+		}
+		AstNode *first = &l.vals[0];
+		if (first->ty != AST_SYMBOL) {
+			printf("first element of list must be symbol\n");
+			return 0;
+		}
+		return call_builtin(first->as.str, l);
+		break;
+	default:
+		printf("???\n");
+		return 0;
+	}
+}
+