From 623964374a265f145fd40fec4e3640a90094dd53 Mon Sep 17 00:00:00 2001
From: sfj <sfj@skov.dk>
Date: Wed, 10 Sep 2025 15:43:53 +0200
Subject: [PATCH] js gen + syntax

---
 .gitignore                              |   1 +
 compile.phi                             | 326 +++++++++++++++-
 phi.js                                  | 474 +++++++++++++++++-------
 program.phi                             |   1 -
 vim/syntax/phi.vim                      |   2 +-
 vscode/install.sh                       |   7 +
 vscode/phi/syntaxes/phi.tmLanguage.json |  36 +-
 7 files changed, 674 insertions(+), 173 deletions(-)
 create mode 100644 .gitignore

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..641a92d
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+out.js
diff --git a/compile.phi b/compile.phi
index 1a18172..6a576bb 100644
--- a/compile.phi
+++ b/compile.phi
@@ -1,6 +1,198 @@
 
-(let identChars "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890+-*/%&|=?!<>'_")
+(fn Emitter (ast) (do
+    (let output ())
 
+    (fn generate () (do
+        (call emit "#!/usr/bin/env node\n")
+        (call emit_exprs ast)
+        (return (call strings_join output))
+    ))
+
+    (fn emit_exprs (exprs) (do
+        (for expr exprs (do
+            (call emit_expr expr)
+            (call emit "\n")
+        ))
+    ))
+
+    (fn emit_expr (expr) (do
+        (let (ty line) expr)
+        (if (== ty "list") (do
+            (call emit_list expr)
+        ) (if (== ty "int") (
+            (let (_ _ value) expr)
+            (call emit (call format "%" value))
+        ) (if (== ty "string") (
+            (let (_ _ value) expr)
+            (call emit (call format "\"%\"" (call string_escape value)))
+        ) (if (== ty "ident") (
+            (let (_ _ value) expr)
+            (call emit (call format "_%" value))
+        ) (do
+            (call panic "unknown expr type '%' on line %" ty line)
+        )))))
+    ))
+
+    (fn emit_list (expr) (do
+        (let (ty line s) expr)
+        (if (== (call len s) 0) (do
+            (call emit "[]")
+            (return)
+        ))
+        (let ((_ _ id)) s)
+        (if (== id "fn") (do
+            (let (_ (_ _ name) (_ _ params) body) s)
+            (call emit (call format "function _%(" name))
+
+            (let first true)
+            (for (_ _ name) params (do
+                (if (not first) (do
+                    (call emit ", ")
+                ))
+                (= first false)
+
+                (call emit (call format "_%" name))
+            ))
+            (call emit (call format ") {\n" name))
+            (call emit_expr body)
+            (call emit "}")
+        ) (if (== id "do") (do
+            (call emit_exprs (call slice s 1))
+        ) (if (== id "return") (do
+            (let (_ value) s)
+            (call emit "return ")
+            (if (!= value null) (do
+                (call emit_expr value)
+            ) (do
+                (call emit "null")
+            ))
+            (call emit ";")
+        ) (if (== id "call") (do
+            (let (_ callee) s)
+            (let args (call slice s 2))
+            (call emit_expr callee)
+            (call emit "(")
+
+            (let first true)
+            (for arg args (do
+                (if (not first) (do
+                    (call emit ", ")
+                ))
+                (= first false)
+
+                (call emit_expr arg)
+            ))
+
+            (call emit ")")
+        ) (do
+            (call emit "[")
+            (let first true)
+            (for e s (do
+                (if (not first) (do
+                    (call emit ", ")
+                ))
+                (= first false)
+
+                (call emit_expr e)
+            ))
+            (call emit "]")
+        )))))
+    ))
+
+    (fn emit (str) (do
+        (call push output str)
+    ))
+
+    (return (generate))
+))
+
+(fn string_escape (str) (do
+    (let str_len (call len str))
+    (let i 0)
+    (let result "")
+    (loop (do
+        (if (>= i str_len) (break))
+        (let ch (call at str i))
+        (if (== ch "\"") (do
+            (+= result "\\\"")
+        ) (if (== ch "\t") (do
+            (+= result "\\t")
+        ) (if (== ch "\r") (do
+            (+= result "\\r")
+        ) (if (== ch "\n") (do
+            (+= result "\\n")
+        ) (if (== ch "\0") (do
+            (+= result "\\0")
+        ) (do
+            (+= result ch)
+        ))))))
+        (+= i 1)
+    ))
+    (return result)
+))
+
+(fn Parser (tokens) (do
+    (let i 0)
+    (let tok (call at tokens i))
+
+    (fn parse () (do
+        (let exprs ())
+        (loop (do
+            (if (call done) (break))
+            (call push exprs (call parse_expr))
+        ))
+        (return exprs)
+    ))
+
+    (fn parse_expr () (do
+        (let (ty line value) tok)
+        (if (call eat "(") (do
+            (let values ())
+            (loop (do
+                (if (call test ")") (break))
+                (call push values (call parse_expr))
+            ))
+            (if (not (call eat ")")) (do
+                (call panic "expected ')' on line %" (call at tok 1))
+            ))
+            (return ("list" line values))
+        ) (if (call eat "string") (do
+            (return ("string" line value))
+        ) (if (call eat "int") (do
+            (return ("int" line (call string_to_int value)))
+        ) (if (call eat "ident") (do
+            (return ("ident" line value))
+        ) (do
+            (call panic "expected expression, got '%' on line %" ty line)
+        )))))
+    ))
+
+    (fn eat (pat) (do
+        (if (not (call test pat)) (return false))
+        (call step)
+        (return true)
+    ))
+
+    (fn step () (do
+        (+= i 1)
+        (if (not (call done)) (do
+            (let new_tok (call at tokens i))
+            (= tok new_tok)
+        ))
+    ))
+
+    (fn test (pat) (do
+        (if (call done) (return false))
+        (let (ty) tok)
+        (return (== pat ty))
+    ))
+
+    (fn done () (do
+        (return (>= i (call len tokens)))
+    ))
+
+    (return (parse))
+))
 
 (fn tokenize (text) (do
     (let text_len (call len text))
@@ -15,14 +207,13 @@
         (let ch (call at text i))
 
         (if (call contains " \t\r\n" ch) (do
-            (call println "line = %, ch = '%'" line ch)
             (if (== ch "\n") (do
                 (+= line 1)
             ))
             (+= i 1)
         ) (if (call slice_eq text i "//") (do
             (loop (do
-                if (or (>= i text_len) (== (call at text i) "\n") (do
+                (if (or (>= i text_len) (== (call at text i) "\n")) (do
                     (break)
                 ))
                 (+= i 1)
@@ -31,8 +222,52 @@
             (call push tokens (ch line))
             (+= i 1)
         ) (if (== ch "\"") (do
-            
+            (let value "")
             (+= i 1)
+            (= ch (call at text i))
+            (loop (do
+                (if (or (>= i text_len) (== ch "\"")) (do
+                    (break)
+                ))
+                (if (== ch "\\") (do
+                    (+= i 1)
+                    (if (>= i text_len) (do
+                        (break)
+                    ))
+                    (= ch (call at text i))
+                    (if (== ch "t") (do
+                        (+= value "\t")
+                    ) (if (== ch "r") (do
+                        (+= value "\r")
+                    ) (if (== ch "n") (do
+                        (+= value "\n")
+                    ) (if (== ch "0") (do
+                        (+= value "\n")
+                    ) (do
+                        (+= value ch)
+                    )))))
+                ) (do
+                    (+= value ch)
+                ))
+                (+= i 1)
+                (= ch (call at text i))
+            ))
+            (if (or (>= i text_len) (!= ch "\"") (do
+                (call panic "expected '\"' on line %" line)
+            )))
+            (+= i 1)
+            (call push tokens ("string" line value))
+        ) (if (call contains "0123456789" ch) (do
+            (let value "")
+            (loop (do
+                (= ch (call at text i))
+                (if (or (>= i text_len) (not (call contains "0123456789" ch))) (do
+                    (break)
+                ))
+                (+= value ch)
+                (+= i 1)
+            ))
+            (call push tokens ("int" line value))
         ) (if (call contains identChars ch) (do
             (let value "")
             (loop (do
@@ -40,19 +275,22 @@
                 (if (or (>= i text_len) (not (call contains identChars ch))) (do
                     (break)
                 ))
-                (call push value ch)
+                (+= value ch)
                 (+= i 1)
             ))
             (call push tokens ("ident" line value))
         ) (do
             (call println "illegal char '%'" ch)
             (+= i 1)
-        ))))))
+        )))))))
         
     ))
     (return tokens)
 ))
 
+(let identChars (+ "abcdefghijklmnopqrstuvwxyz"
+    "ABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890+-*/%&|=?!<>'_"))
+
 (fn contains (text ch) (do
     (let text_len (call len text))
     (let i 0)
@@ -69,9 +307,11 @@
 (fn slice_eq (str slice_idx substr) (do
     (let str_len (call len str))
     (let substr_len (call len substr))
-    (let i slice_idx)
+    (let i 0)
     (loop (do
-        (if (or (>= (+ slice_idx i) str_len) (>= i substr_len))
+        (if (>= i substr_len)
+            (return true))
+        (if (>= (+ slice_idx i) str_len)
             (return false))
         (if (!= (call at str (+ slice_idx i)) (call at substr i))
             (return false))
@@ -80,14 +320,76 @@
     (return true)
 ))
 
+(fn print_expr (expr depth) (do
+    (let (ty line value) expr)
+    (if (== ty "list") (do
+        (call println "%(% %" (call indent depth) ty line)
+        (for e value (do
+            (call print_expr e (+ depth 1))
+        ))
+        (call println "%)" (call indent depth))
+    ) (do
+        (call println "%%" (call indent depth) expr)
+    ))
+))
+
+(fn indent (depth) (do
+    (let space "")
+    (let i 0)
+    (loop (do
+        (if (>= i depth) (break))
+        (+= space "  ")
+        (+= i 1)
+    ))
+    (return space)    
+))
+
+(fn slice (list idx) (do
+    (let list_len (call len list))
+    (let elems ())
+    (let i idx)
+    (loop (do
+        (if (>= i list_len) (break))
+        (call push elems (call at list i))
+        (+= i 1)
+    ))
+    (return elems)
+))
+
 (let text (call read_text_file "program.phi"))
 
-(let tokens (call tokenize text))
-
+(call println "reading file...")
 (call println "=== text ===")
 (call println text)
+
+(call println "tokenizing...")
+(let tokens (call tokenize text))
+
 (call println "=== tokens ===")
-(call println tokens)
-(call println (+ 1 2))
+(for (tok line value) tokens (do
+    (call println "%\t%\t%" line tok (if (!= value null) value ""))
+))
+
+(call println "parsing...")
+(let parser (call Parser tokens))
+(let (parse) parser)
+(let ast (call parse))
+
+(call println "=== ast ===")
+(for expr ast (do
+    (call print_expr expr 0)
+))
+
+(call println "emitting...")
+(let emitter (call Emitter ast))
+(let (emit) emitter)
+(let js_code (call emit))
+
+(call println "=== js ===")
+(call println js_code)
+
+(call println "writing file...")
+(call write_text_file "out.js" js_code)
+
 
 
diff --git a/phi.js b/phi.js
index 6798668..e8f0f6f 100644
--- a/phi.js
+++ b/phi.js
@@ -4,13 +4,14 @@ import * as fs from "node:fs";
 import process from "node:process";
 
 function main() {
-    const text = fs.readFileSync(process.argv[2]).toString();
+    const filename = process.argv[2];
+    const text = fs.readFileSync(filename).toString();
 
     const ast = new Parser(text).parse();
 
     let lastValue = null;
 
-    const evaluator = new Evaluator();
+    const evaluator = new Evaluator(filename);
     for (const expr of ast) {
         const result = evaluator.eval(expr);
         if (result.type !== "value") {
@@ -24,14 +25,22 @@ function main() {
 }
 
 class Evaluator {
-    constructor() {
-        this.syms = { parent: undefined, map: new Map(builtins) };
+    constructor(filename) {
+        this.syms = { parent: undefined, map: new Map(this.builtins) };
+        this.currentLine = 0;
+        this.callStack = [{ name: "<file>", line: 0 }];
+        this.filename = filename;
     }
 
     /**
      * @param {Expr} expr
      */
     eval(expr) {
+        if (!expr) {
+            console.log(this.callStack)
+            throw new Error()
+        }
+        this.currentLine = expr.line;
         if (expr.type === "list") {
             return this.evalList(expr, expr.line);
         } else if (expr.type === "int") {
@@ -48,7 +57,11 @@ class Evaluator {
                     `could not find symbol '${expr.value}' on line ${expr.line}`,
                 );
             }
-            return { type: "value", value: sym };
+            if (sym.type === "local") {
+                return { type: "value", value: { ...sym.value } };
+            } else {
+                return { type: "value", value: { ...sym } };
+            }
         } else {
             throw new Error(
                 `unknown expr type '${expr.type}' on line ${expr.line}`,
@@ -68,97 +81,29 @@ class Evaluator {
         const s = expr.values;
         const id = s[0]?.type === "ident" ? s[0].value : undefined;
         if (id === "fn") {
-            const name = s[1].value;
-            this.syms.map.set(name, {
-                type: "fn",
-                name,
-                params: s[2].values.map((ident) => ident.value),
-                body: s[3],
-                syms: this.syms,
-            });
-            return { type: "value", value: { type: "null" } };
+            return this.evalFn(expr);
         } else if (id === "return") {
             return {
                 type: "return",
                 value: s[1] ? this.evalToValue(s[1]) : { type: "null" },
             };
         } else if (id === "let") {
-            const value = this.evalToValue(s[2]);
-            this.syms.map.set(s[1].value, value);
-            return { type: "value", value: { type: "null" } };
+            return this.evalLet(expr);
         } else if (id === "if") {
-            const cond = this.evalToValue(s[1]);
-            if (cond.type !== "bool") {
-                throw new Error(
-                    `expected bool on line ${expr.line}`,
-                );
-            }
-            if (cond.value) {
-                return this.eval(s[2]);
-            } else if (s[3]) {
-                return this.eval(s[3]);
-            } else {
-                return { type: "value", value: "null" };
-            }
+            return this.evalIf(expr);
         } else if (id === "loop") {
-            while (true) {
-                const result = this.eval(s[1]);
-                if (result.type === "break") {
-                    return { type: "value", value: result.value };
-                } else if (result.type !== "value") {
-                    return result;
-                }
-            }
+            return this.evalLoop(expr);
+        } else if (id === "for") {
+            return this.evalFor(expr);
         } else if (id === "break") {
             return {
                 type: "break",
                 value: s[1] ? this.evalToValue(s[1]) : { type: "null" },
             };
         } else if (id === "do") {
-            let lastValue = { type: "null" };
-
-            for (const expr of s.slice(1)) {
-                const result = this.eval(expr);
-                if (result.type !== "value") {
-                    return result;
-                }
-                lastValue = result.value;
-            }
-            return { type: "value", value: lastValue };
+            return this.evalDo(expr);
         } else if (id === "call") {
-            const args = s.slice(2).map((arg) => this.evalToValue(arg));
-            const fnValue = this.evalToValue(s[1]);
-
-            if (fnValue.type === "builtin") {
-                return { type: "value", value: fnValue.fn(...args) };
-            } else if (fnValue.type !== "fn") {
-                throw new Error("cannot call non-function");
-            }
-            const callerSyms = this.syms;
-            this.syms = {
-                parent: fnValue.syms,
-                map: new Map(),
-            };
-            if (fnValue.params.length !== args.length) {
-                throw new Error(
-                    `incorrect amount of arguments on line ${line}`,
-                );
-            }
-            for (let i = 0; i < fnValue.params.length; ++i) {
-                this.syms.map.set(fnValue.params[i], args[i]);
-            }
-
-            let returnValue = { type: "null" };
-            const result = this.eval(fnValue.body);
-
-            if (result.type === "value" || result.type === "return") {
-                returnValue = result.value;
-            } else {
-                throw new Error(`illegal ${result.type} across boundry`);
-            }
-
-            this.syms = callerSyms;
-            return { type: "value", value: returnValue };
+            return this.evalCall(expr);
         } else if (id === "not") {
             const value = this.evalToValue(s[1]);
             return {
@@ -181,44 +126,31 @@ class Evaluator {
             } else {
                 return { type: "value", value: left };
             }
-        } else if (id in artithmeticOps) {
+        } else if (id in this.artithmeticOps) {
             const left = this.evalToValue(s[1]);
             const right = this.evalToValue(s[2]);
+            if (id === "+" && left.type === "string" && right.type === "string") {
+                return { type: "value", value: { type: "string", value: left.value + right.value } };
+            }
             return {
                 type: "value",
                 value: {
                     type: "int",
-                    value: artithmeticOps[id](left.value, right.value),
+                    value: this.artithmeticOps[id](left.value, right.value),
                 },
             };
-        } else if (id in comparisonOps) {
+        } else if (id in this.comparisonOps) {
             const left = this.evalToValue(s[1]);
             const right = this.evalToValue(s[2]);
             return {
                 type: "value",
                 value: {
                     type: "bool",
-                    value: comparisonOps[id](left.value, right.value),
+                    value: this.comparisonOps[id](left.value, right.value),
                 },
             };
-        } else if (id in assignOps) {
-            if (s[1].type === "ident") {
-                const sym = this.findSym(s[1].value);
-                if (!sym) {
-                    throw new Error(
-                        `could not find symbol '${expr.value}' on line ${expr.line}`,
-                    );
-                }
-                const right = this.evalToValue(s[2]);
-                const newValue = assignOps[id](sym, right);
-                sym.type = newValue.type;
-                sym.value = newValue.value;
-            } else {
-                throw new Error(
-                    `cannot assign to expression on line ${expr.line}`,
-                );
-            }
-            return { type: "value", value: { type: "null" } };
+        } else if (id in this.assignOps) {
+            return this.evalAssign(expr);
         } else {
             return {
                 type: "value",
@@ -230,6 +162,196 @@ class Evaluator {
         }
     }
 
+    evalFn(expr) {
+        const s = expr.values;
+        const name = s[1].value;
+        this.syms.map.set(name, {
+            type: "fn",
+            line: expr.line,
+            name,
+            params: s[2].values.map((ident) => ident.value),
+            body: s[3],
+            syms: this.syms,
+        });
+        return { type: "value", value: { type: "null" } };
+    }
+
+    evalLet(expr) {
+        const s = expr.values;
+        const value = this.evalToValue(s[2]);
+        this.assignPattern(s[1], value);
+        return { type: "value", value: { type: "null" } };
+    }
+
+    evalIf(expr) {
+        const s = expr.values;
+        const cond = this.evalToValue(s[1]);
+        if (cond.type !== "bool") {
+            throw new Error(
+                `expected bool on line ${expr.line}`,
+            );
+        }
+        if (cond.value) {
+            return this.eval(s[2]);
+        } else if (s[3]) {
+            return this.eval(s[3]);
+        } else {
+            return { type: "value", value: "null" };
+        }
+    }
+
+    evalLoop(expr) {
+        const s = expr.values;
+        while (true) {
+            const result = this.eval(s[1]);
+            if (result.type === "break") {
+                return { type: "value", value: result.value };
+            } else if (result.type !== "value") {
+                return result;
+            }
+        }
+    }
+
+    evalFor(expr) {
+        const s = expr.values;
+
+        const value = this.evalToValue(s[2]);
+        if (value.type !== "list") {
+            throw new Error(
+                `expected list on line ${expr.line}`,
+            );
+        }
+
+        const outerSyms = this.syms;
+        this.syms = { parent: outerSyms, map: new Map() };
+
+        for (let i = 0; i < value.values.length; ++i) {
+            this.assignPattern(s[1], value.values[i]);
+            const result = this.eval(s[3]);
+            if (result.type === "break") {
+                return { type: "value", value: result.value };
+            } else if (result.type !== "value") {
+                return result;
+            }
+        }
+        this.syms = outerSyms;
+        return { type: "value", value: { type: "null" } }
+    }
+
+    evalDo(expr) {
+        const s = expr.values;
+        const outerSyms = this.syms;
+        this.syms = { parent: outerSyms, map: new Map() };
+
+        let lastValue = { type: "null" };
+
+        for (const expr of s.slice(1)) {
+            const result = this.eval(expr);
+            if (result.type !== "value") {
+                return result;
+            }
+            lastValue = result.value;
+        }
+
+        this.syms = outerSyms;
+        return { type: "value", value: lastValue };
+    }
+
+    evalCall(expr) {
+        const s = expr.values;
+        const args = s.slice(2).map((arg) => this.evalToValue(arg));
+        const fnValue = this.evalToValue(s[1]);
+
+        if (fnValue.type === "builtin") {
+            return { type: "value", value: fnValue.fn(...args) };
+        } else if (fnValue.type !== "fn") {
+            throw new Error("cannot call non-function");
+        }
+
+        if (this.callStack.length > 100) {
+            this.panic("stack overflow")
+            this.printCallStack()
+            process.exit(1);
+        }
+
+        this.callStack.push({ name: fnValue.name, line: expr.line });
+        const callerSyms = this.syms;
+        this.syms = {
+            parent: fnValue.syms,
+            map: new Map(),
+        };
+        if (fnValue.params.length !== args.length) {
+            throw new Error(
+                `incorrect amount of arguments for function '${fnValue.name}' on line ${expr.line}`,
+            );
+        }
+        for (let i = 0; i < fnValue.params.length; ++i) {
+            this.syms.map.set(fnValue.params[i], args[i]);
+        }
+
+        let returnValue = { type: "null" };
+        const result = this.eval(fnValue.body);
+
+        if (result.type === "value" || result.type === "return") {
+            returnValue = result.value;
+        } else {
+            throw new Error(`illegal ${result.type} across boundry`);
+        }
+
+        this.syms = callerSyms;
+        this.callStack.pop()
+        return { type: "value", value: returnValue };
+    }
+
+    evalAssign(expr) {
+        const s = expr.values;
+        const id = s[0].value;
+        if (s[1].type === "ident") {
+            const sym = this.findSym(s[1].value);
+            if (!sym) {
+                throw new Error(
+                    `could not find symbol '${expr.value}' on line ${expr.line}`,
+                );
+            }
+            const value = this.evalToValue(s[2]);
+            if (sym.type === "local") {
+                sym.value = this.assignOps[id](sym.value, value);
+            } else {
+                throw new Error(
+                    `cannot assign to symbol on line ${expr.line}`,
+                );
+            }
+        } else {
+            throw new Error(
+                `cannot assign to expression on line ${expr.line}`,
+            );
+        }
+        return { type: "value", value: { type: "null" } };
+    }
+
+    /** @param {Expr} pattern */
+    assignPattern(pattern, value) {
+        if (pattern.type === "ident") {
+            if (pattern.value === "_") {
+                return;
+            }
+            this.syms.map.set(pattern.value, {
+                type: "local",
+                line: pattern.line,
+                value,
+            });
+        } else if (pattern.type === "list") {
+            if (value.type !== "list") {
+                throw new Error(`expected list on line ${pattern.line}`);
+            }
+            for (const [i, p] of pattern.values.entries()) {
+                this.assignPattern(p, value.values[i] ?? { type: "null" })
+            }
+        } else {
+            throw new Error(`cannot assign to pattern on line ${pattern.line}`);
+        }
+    }
+
     findSym(ident, syms = this.syms) {
         if (syms.map.has(ident)) {
             return syms.map.get(ident);
@@ -239,28 +361,30 @@ class Evaluator {
             return undefined;
         }
     }
-}
 
-const artithmeticOps = {
-    "+": (left, right) => right + left,
-    "-": (left, right) => right - left,
-};
-const comparisonOps = {
-    "==": (left, right) => left === right,
-    "!=": (left, right) => left !== right,
-    "<": (left, right) => left < right,
-    ">": (left, right) => left > right,
-    "<=": (left, right) => left <= right,
-    ">=": (left, right) => left >= right,
-};
-const assignOps = {
-    "=": (_, right) => right,
-    "+=": (left, right) => ({ type: "int", value: left.value + right.value }),
-    "-=": (left, right) => ({ type: "int", value: left.value - right.value }),
-};
+    panic(msg) {
+        console.error(`\x1b[1;91mpanic\x1b[1;97m: ${msg}\x1b[0m"`);
+        this.printCallStack();
+    }
 
-const builtinFns = {
-    println(msg, ...args) {
+    printCallStack() {
+        const last = this.callStack[this.callStack.length - 1];
+        console.error(`    \x1b[90mat \x1b[37m${last.name} \x1b[90m(${this.filename}:${this.currentLine})\x1b[0m`);
+        for (let i = this.callStack.length - 2; i >= 0; --i) {
+            const name = this.callStack[i].name;
+            const line = this.callStack[i + 1].line;
+            console.error(`    \x1b[90mat \x1b[37m${name} \x1b[90m(${this.filename}:${line})\x1b[0m`);
+        }
+    }
+
+    builtinFormat(msg, ...args) {
+        let value = valueToPrint(msg);
+        for (const arg of args) {
+            value = value.replace("%", valueToPrint(arg));
+        }
+        return { type: "string", value };
+    }
+    builtinPrintln(msg, ...args) {
         let text = valueToPrint(msg);
 
         for (const arg of args) {
@@ -269,44 +393,108 @@ const builtinFns = {
 
         console.log(text);
         return { type: "null" };
-    },
-    read_text_file(path) {
+    }
+    builtinPanic(msg, ...args) {
+        let text = valueToPrint(msg);
+
+        for (const arg of args) {
+            text = text.replace("%", valueToPrint(arg));
+        }
+
+        this.panic(text);
+        process.exit(1);
+        return { type: "null" };
+    }
+    builtinReadTextFile(path) {
         const text = fs.readFileSync(path.value).toString();
         return { type: "string", value: text };
-    },
-    push(list, value) {
+    }
+    builtinWriteTextFile(path, text) {
+        fs.writeFileSync(path.value, text.value);
+        return { type: "null" };
+    }
+    builtinPush(list, value) {
         if (list.type === "string") {
             list.value += value.value;
             return list;
         }
         list.values.push(value);
         return list;
-    },
-    at(value, index) {
+    }
+    builtinAt(value, index) {
         if (value.type === "string") {
             return { type: "string", value: value.value[index.value] };
         }
         return value.values[index.value];
-    },
-    len(value) {
+    }
+    builtinLen(value) {
         if (value.type === "string") {
             return { type: "int", value: value.value.length };
         }
         return { type: "int", value: value.values.length };
-    },
-};
+    }
+    builtinStringToInt(value) {
+        return { type: "int", value: Number(value.value) };
+    }
+    builtinCharCode(value) {
+        return { type: "int", value: value.value.charCodeAt(0) };
+    }
+    builtinStringsJoin(value) {
+        return {
+            type: "string",
+            value: value.values
+                .map(value => value.value)
+                .join("")
+        };
+    }
 
-const consts = {
-    "null": { type: "null" },
-    "false": { type: "bool", value: false },
-    "true": { type: "bool", value: true },
-};
+    artithmeticOps = {
+        "+": (left, right) => right + left,
+        "-": (left, right) => right - left,
+    };
+    comparisonOps = {
+        "==": (left, right) => left === right,
+        "!=": (left, right) => left !== right,
+        "<": (left, right) => left < right,
+        ">": (left, right) => left > right,
+        "<=": (left, right) => left <= right,
+        ">=": (left, right) => left >= right,
+    };
+    assignOps = {
+        "=": (_, right) => right,
+        "+=": (left, right) => ({
+            type: left.type === "string" && left.type === right.type ? "string" : "int",
+            value: left.value + right.value
+        }),
+        "-=": (left, right) => ({ type: "int", value: left.value - right.value }),
+    };
 
-const builtins = [
-    ...Object.entries(builtinFns)
-        .map(([key, fn]) => [key, { type: "builtin", fn }]),
-    ...Object.entries(consts),
-];
+    builtinFns = {
+        "format": (...args) => this.builtinFormat(...args),
+        "println": (...args) => this.builtinPrintln(...args),
+        "panic": (...args) => this.builtinPanic(...args),
+        "read_text_file": (...args) => this.builtinReadTextFile(...args),
+        "write_text_file": (...args) => this.builtinWriteTextFile(...args),
+        "push": (...args) => this.builtinPush(...args),
+        "at": (...args) => this.builtinAt(...args),
+        "len": (...args) => this.builtinLen(...args),
+        "string_to_int": (...args) => this.builtinStringToInt(...args),
+        "char_code": (...args) => this.builtinCharCode(...args),
+        "strings_join": (...args) => this.builtinStringsJoin(...args),
+    };
+
+    consts = {
+        "null": { type: "null" },
+        "false": { type: "bool", value: false },
+        "true": { type: "bool", value: true },
+    };
+
+    builtins = [
+        ...Object.entries(this.builtinFns)
+            .map(([key, fn]) => [key, { type: "builtin", fn }]),
+        ...Object.entries(this.consts),
+    ];
+}
 
 function valueToPrint(value) {
     if (value.type === "null") {
diff --git a/program.phi b/program.phi
index 10ded09..2f47e27 100644
--- a/program.phi
+++ b/program.phi
@@ -1,4 +1,3 @@
-
 (fn hello () (do
     (call println "hello world")
     (call println "hello world")
diff --git a/vim/syntax/phi.vim b/vim/syntax/phi.vim
index 3fb443e..0d348e0 100644
--- a/vim/syntax/phi.vim
+++ b/vim/syntax/phi.vim
@@ -8,7 +8,7 @@ if exists("b:current_syntax")
 endif
 
 
-syn keyword Keyword fn call return loop break if let do
+syn keyword Keyword fn call return loop for break if let do
 syn keyword Operator and or not
 syn keyword Special null
 syn keyword Boolean true false
diff --git a/vscode/install.sh b/vscode/install.sh
index c485fa5..e385860 100644
--- a/vscode/install.sh
+++ b/vscode/install.sh
@@ -2,6 +2,13 @@
 
 set -xe
 
+if [ $# -eq 0 ]
+then
+    echo "No VS Code location specified."
+    echo "USAGE: ./install.sh <vscode location>"
+    echo "EXAMPLE: ./install.sh ~/.vscode"
+fi
+
 SCRIPT_DIR=$(dirname "${BASH_SOURCE[0]}")
 CODE_PATH=$1
 
diff --git a/vscode/phi/syntaxes/phi.tmLanguage.json b/vscode/phi/syntaxes/phi.tmLanguage.json
index d7d7ff5..de67758 100644
--- a/vscode/phi/syntaxes/phi.tmLanguage.json
+++ b/vscode/phi/syntaxes/phi.tmLanguage.json
@@ -2,28 +2,32 @@
 	"$schema": "https://raw.githubusercontent.com/martinring/tmlanguage/master/tmlanguage.json",
 	"name": "phi",
 	"patterns": [
-		{
-			"include": "#keywords"
-		},
-		{
-			"include": "#operators"
-		},
-		{
-			"include": "#numbers"
-		},
-		{
-			"include": "#strings"
-		},
-		{
-			"include": "#idents"
-		}
+        { "include": "#comments" },
+		{ "include": "#keywords" },
+		{ "include": "#operators" },
+		{ "include": "#numbers" },
+		{ "include": "#strings" },
+		{ "include": "#idents" }
 	],
 	"repository": {
+        "comments": {
+            "patterns": [
+                {
+                    "name": "comment.line.phi",
+                    "begin": "//",
+                    "end": "\\n"
+                }
+            ]
+        },
 		"keywords": {
 			"patterns": [
 				{
 					"name": "keyword.control.phi",
-					"match": "\\b(fn|call|return|loop|break|if|let|do)\\b"
+					"match": "\\b(fn|return|loop|for|break|if|do|call)\\b"
+				},
+				{
+					"name": "storage.type.phi",
+					"match": "\\b(let)\\b"
 				},
 				{
 					"name": "keyword.operator.phi",