2 files changed, 61 insertions, 3 deletions
diff --git a/src/lib/core/eval.ts b/src/lib/core/eval.ts
index 779bfd9..7c2c91b 100644
--- a/src/lib/core/eval.ts
+++ b/src/lib/core/eval.ts
@@ -1,7 +1,55 @@
-import { ASTNode } from "./common";
+import { ASTNode, NodeType } from "./common";
 import { Lex } from "./lexer";
 import { Parse } from "./parser";
 
-export type Evaluate<Node extends ASTNode> = "Not implemented";
+export type FnError<T extends string> = `Function execution error: ${T}`;
 
-const test_result = null as unknown as Evaluate<Parse<Lex<"print(a)">>>;
+export type ToStringInner<T, Carry extends string = ""> = T extends
+  | string
+  | number
+  ? `${T}`
+  : T extends readonly any[]
+  ? T extends [infer Head, ...infer Tail]
+    ? `${ToStringInner<
+        Tail,
+        `${Carry extends "" ? "" : `${Carry}, `}${ToStringInner<Head>}`
+      >}`
+    : `[${Carry}]`
+  : FnError<`Can't stringify`>;
+
+export type BUILTIN_ToString<Args extends readonly ASTNode[]> = {
+  [Idx in Exclude<keyof Args, keyof any[]>]: Args[Idx] extends ASTNode
+    ? ToStringInner<Evaluate<Args[Idx]>>
+    : never;
+};
+// export type BUILTIN_Print<Args extends readonly ASTNode[]>
+
+export type SENTINEL_NO_BUILTIN = "__NO_BUILTIN__";
+export type MapBuiltins<Node extends ASTNode> = Node["name"] extends "tostring"
+  ? BUILTIN_ToString<Node["children"]>
+  : SENTINEL_NO_BUILTIN;
+
+export type EvalError<T extends string> = `Eval error: ${T}`;
+
+export type Evaluate<Node extends ASTNode> = Node["type"] extends NodeType.INT
+  ? Node["value"]
+  : Node["type"] extends NodeType.ROOT
+  ? {
+      // FIXME render as array??
+      [Idx in Exclude<
+        keyof Node["children"],
+        keyof any[]
+      >]: Node["children"][Idx] extends ASTNode
+        ? Evaluate<Node["children"][Idx]>
+        : never;
+      // indexing for now to remove object syntax
+      // pls fix
+    }[Exclude<keyof Node["children"], keyof any[]>]
+  : Node["type"] extends NodeType.EXT
+  ? MapBuiltins<Node>
+  : EvalError<`Unhandled node type ${Node["type"]}`>;
+
+const input = `tostring(5, 3)` as const;
+const lex_result = null as unknown as Lex<typeof input>;
+const parse_result = null as unknown as Parse<typeof lex_result>;
+const eval_result = null as unknown as Evaluate<typeof parse_result>;
diff --git a/src/lib/core/parser.ts b/src/lib/core/parser.ts
index d608eca..27133b2 100644
--- a/src/lib/core/parser.ts
+++ b/src/lib/core/parser.ts
@@ -199,6 +199,16 @@ export type _Parse<Ctx extends ParserCtx> = Ctx["remainingTokens"] extends [
       }>
     : Ctx &
         Error<`Expected nextToken to be a name or close paren at ${Head["type"]}`>
+  : Ctx["lastToken"] extends Token
+  ? // case where we ended with a name
+    _Parse<{
+      lastToken: null;
+      remainingTokens: [];
+      stack: PushChildToLastElementOfStack<
+        Ctx["stack"],
+        ResolveNodeFromToken<Ctx["lastToken"]>
+      >;
+    }>
   : Ctx["stack"][0];
 
 export type Parse<Raw extends readonly Token[]> = _Parse<{