From 34d43452cbdbd7334e1aa8984e05b3d7841c1791 Mon Sep 17 00:00:00 2001
From: "Aidan K. Ewart" <aidanprattewart@gmail.com>
Date: Sat, 30 May 2020 20:51:47 +0100
Subject: [PATCH] added builtin declaration eazy functions

---
 eval.mjs | 17 +++++++++++------
 main.js  | 21 ++++++++++++++++++++-
 2 files changed, 31 insertions(+), 7 deletions(-)

diff --git a/eval.mjs b/eval.mjs
index 39f4afc..9075094 100644
--- a/eval.mjs
+++ b/eval.mjs
@@ -68,9 +68,6 @@ const fst = (_, args) => [args[0].fst];
 
 const snd = (_, args) => [args[0].snd];
 
-const tru = (_, args) => [args[0]];
-const fls = (_, args) => [args[1]];
-
 const eq = (_, args) => {
     if (args[0].type === args[1].type && args[0].val === args[1].val) {
         return [{type:"ident", val:"true"}];
@@ -79,13 +76,15 @@ const eq = (_, args) => {
     }
 }
 
+const stop = (a, b) => {
+    return [{type:"string", val:"stop"}];
+}
+
 let builtinDefn = {
     "+":        makeEval(["int", "int"], add),
     "-":        makeEval(["int", "int"], sub),
     "/":        makeEval(["int", "int"], div),
     "*":        makeEval(["int", "int"], mult),
-    "true":     makeEval(2, tru),
-    "false":    makeEval(2, fls),
     "==":       makeEval(2, eq),
     "typeof":   makeEval(1, type),
     "pair":     makeEval(2, pair),
@@ -97,6 +96,10 @@ export const addDefn = (name, sign, func) => {
     builtinDefn[name] = makeEval(sign, func);
 }
 
+export const addRPNASTDefn = (name, ast) => {
+    builtinDefn[name] = makeLambda(ast);
+}
+
 const makeLambda = (lambda) => {
     return {nargs:lambda.args.length, defn:(scope, args) => {
         let newscope = Object.create(scope); // I am so sorry...
@@ -151,7 +154,9 @@ const giveArg = (closure, arg, scope) => {
 
 const apply = (elem, stack) => {
     if (elem.type === "closure") {
-        if (stack.stack.length > 0) {
+        if (elem.func.nargs === 0) {
+            applyMany(elem.func.defn(stack.scope, []), stack);
+        } else if (stack.stack.length > 0) {
             let out = giveArg(elem, stack.stack.pop(), stack.scope);
             applyMany(out, stack);
         } else {
diff --git a/main.js b/main.js
index 04d5582..c72a7ac 100644
--- a/main.js
+++ b/main.js
@@ -1,4 +1,4 @@
-import {execRPN} from './eval.mjs';
+import {execRPN, addRPNASTDefn} from './eval.mjs';
 import {parseExprs} from './parse.mjs';
 import {tokenize} from './token.mjs';
 
@@ -29,6 +29,25 @@ const prettyprint = (out) => {
     return str;
 }
 
+const addRPNBuiltin = (name, def) => {
+    let toks = tokenize(def);
+    if (!toks) {
+        throw 'could not load builtin'
+    }
+    let ast = parseExprs(toks);
+    if (!ast.parsed) {
+        throw 'could not load builtin'
+    }
+    console.log(ast);
+    addRPNASTDefn(name, ast.parsed[0]);
+}
+
+addRPNBuiltin("true", "(a b -> a)");
+addRPNBuiltin("false", "(a b -> b)");
+addRPNBuiltin("stop", "(-> \"stop)");
+addRPNBuiltin("id", "(a -> a)");
+addRPNBuiltin("fold", "(fn acc x -> '(-> x acc fn 'fn fold) '(-> acc) 'x \"stop ==)");
+
 submit.onclick = (event) => {
     const input = inbox.value;
     let toks = tokenize(input);