Add lexical scope supportHEADmaster

1 files changed, 74 insertions, 5 deletions

diff --git a/source/forest.c b/source/forest.c
index 3e756fb..3b01131 100644
--- a/source/forest.c
+++ b/source/forest.c
@@ -12,15 +12,15 @@
 
 #include <gmp.h>
 
+#define NOB_IMPLEMENTATION
+#include "nob.h"
+
 #define ARENA_IMPLEMENTATION
 #include "arena.h"
 
 #define HT_IMPLEMENTATION
 #include "ht.h"
 
-#define NOB_IMPLEMENTATION
-#include "nob.h"
-
 #if defined(Y) || defined(N)
 #error "Can only use stb_c_lexer in contexts where the preprocessor symbols 'Y' and 'N' are not defined"
 #endif
@@ -160,10 +160,73 @@ struct Node {
 };
 
 
+typedef Ht(String_View, Node *) Symbol_Table;
+
+typedef struct Scope Scope;
+struct Scope {
+	Scope *parent;
+	Symbol_Table symbols;
+};
+
+static Scope *
+scope_new(Arena *arena, Scope *parent);
+static void
+scope_free(Scope *scope);
+
+static void
+scope_insert(Scope *scope, String_View name, Node *node);
+static Node *
+scope_lookup(Scope *scope, String_View name);
+static Node *
+scope_lookup_current(Scope *scope, String_View name);
+
+static Scope *
+scope_new(Arena *arena, Scope *parent) {
+	// TODO: We can move the allocation and zeroing to a separate function.
+	Scope *scope = arena_alloc(arena, sizeof(Scope));
+	assert(scope != NULL);
+	memset(scope, 0, sizeof(Scope));
+
+	scope->parent = parent;
+	scope->symbols.hasheq = ht_sv_hasheq;
+
+	return scope;
+}
+
+static void
+scope_free(Scope *scope) {
+	// NOTE: Even if the hash table allocates on the heap, that is fine because
+	//       scopes are meant to be freed individually.
+	ht_free(&scope->symbols);
+}
+
+static void
+scope_insert(Scope *scope, String_View name, Node *node) {
+	*ht_find_or_put(&scope->symbols, name) = node;
+}
+
+static Node *
+scope_lookup(Scope *scope, String_View name) {
+	Node *result = NULL;
+	while (!result && scope) {
+		result = scope_lookup_current(scope, name);
+		scope = scope->parent;
+	}
+	return result;
+}
+
+static Node *
+scope_lookup_current(Scope *scope, String_View name) {
+	return *ht_find(&scope->symbols, name);
+}
+
+
 // TODO: Add diagnostics, symbol table, options, etc.
 typedef struct Context Context;
 struct Context {
 	Arena arena;
+	Scope *global_scope;
+	Scope *current_scope;
 };
 
 
@@ -236,7 +299,7 @@ parser_parse_expr(Parser *parser) {
 
 static Node *
 parser_parse_list(Parser *parser) {
-	// TODO: We can move the allocation and zeroing to a separate function that accepts the context.
+	// TODO: We can move the allocation and zeroing to a separate function.
 	Node *list = arena_alloc(&parser->context->arena, sizeof(Node));
 	assert(list != NULL);
 	memset(list, 0, sizeof(Node));
@@ -259,7 +322,7 @@ parser_parse_list(Parser *parser) {
 
 static Node *
 parser_parse_atom(Parser *parser) {
-	// TODO: We can move the allocation and zeroing to a separate function that accepts the context.
+	// TODO: We can move the allocation and zeroing to a separate function.
 	Node *atom = arena_alloc(&parser->context->arena, sizeof(Node));
 	assert(atom != NULL);
 	memset(atom, 0, sizeof(Node));
@@ -335,6 +398,10 @@ main(int argc, char **argv) {
 		.arena = {0},
 	};
 
+	Scope *scope = scope_new(context.arena, NULL);
+	context.global_scope = scope;
+	context.current_scope = scope;
+
 	Parser parser = {
 		.context = &context,
 		.lexer = {0},
@@ -349,5 +416,7 @@ main(int argc, char **argv) {
 	Node *root = parser_parse(&parser);
 	(void) root;
 
+	scope_free(scope);
+
 	return 0;
 }