cleaning up interpreter. adding more types. fixing function application, handling infix binary ops, added currying

src/ast.ts

@@ -1,6 +1,5 @@
 import type { Value } from './types';
 
-
 // Literals and Variables
 
 export type Literal = {

src/interpreter.ts

@@ -13,28 +13,11 @@ export function evaluate(ast: AST, env: Env): Value {
                 throw new Error(`Unknown variable: ${ast.name}`);
             return val;
 
-        case 'binaryop':
-            const left = evaluate(ast.left, env);
-            const right = evaluate(ast.right, env);
-            return evaluateBinaryOp(ast.operator, left, right);
-
         case 'let':
             const val2 = evaluate(ast.value, env);
             const newEnv = new Map(env).set(ast.name, val2);
             return evaluate(ast.body, newEnv);
 
-        case 'if':
-            const res = evaluate(ast.condition, env);
-
-            if (res.kind !== 'bool')
-                throw new Error('Condition must be bool');
-
-            if (res.value) {
-                return evaluate(ast.then, env);
-            } else {
-                return evaluate(ast.else, env);
-            }
-
         case 'lambda':
             return {
                 kind: 'closure',
@@ -44,21 +27,54 @@ export function evaluate(ast: AST, env: Env): Value {
             }
 
         case 'apply':
+            // Operators
+            if (ast.func.kind === 'variable') {
+                const name = ast.func.name;
+                const builtIns = ['+', '-', '*', '/', '>', '&'];
+
+                if (builtIns.includes(name)) {
+                    const argValues = ast.args.map(arg => evaluate(arg, env));
+
+                    if (argValues.length !== 2) {
+                        throw new Error(`${name} expects 2 args`);
+                    }
+
+                    return evaluateBuiltIn(name, argValues[0], argValues[1]);
+                }
+            }
+
             const func = evaluate(ast.func, env);
+
             if (func.kind !== 'closure')
-                throw new Error('Not a closure');
+                throw new Error('Not a function');
 
-            const params = func.params;
-            const callEnv = new Map(func.env);
-            const args = ast.args;
+            const argValues = ast.args.map(arg => evaluate(arg, env));
 
-            if (args.length !== params.length)
-                throw new Error('Parameter argument mismatch');
+            // Too few args (Currying)
+            if (argValues.length < func.params.length) {
+                // Bind the params we have
+                const newEnv = new Map(func.env);
 
-            for (let i = 0; i < args.length; i++) {
-                const arg = evaluate(args[i], env);
-                const param = params[i];
-                callEnv.set(param, arg);
+                for (let i = 0; i < argValues.length; i++) {
+                    newEnv.set(func.params[i], argValues[i]);
+                }
+
+                return {
+                    kind: 'closure',
+                    params: func.params.slice(argValues.length),
+                    body: func.body,
+                    env: newEnv
+                };
+            }
+
+            // Too many args
+            if (argValues.length > func.params.length)
+                throw new Error('Too many arguments');
+
+            // Exact number of args
+            const callEnv = new Map(func.env);
+            for (let i = 0; i < argValues.length; i++) {
+                callEnv.set(func.params[i], argValues[i]);
             }
 
             return evaluate(func.body, callEnv);
@@ -97,3 +113,17 @@ function evaluateBinaryOp(op: string, left: Value, right: Value): Value {
                 throw new Error(`Unknown operation: ${op}`);
     }
 }
+
+function evaluateBuiltIn(op: string, left: Value, right: Value): Value {
+    if (op === '+' || op === '-' || op === '*' || op === '/') {
+        return evaluateBinaryOp(op, left, right);
+    }
+
+    if (op === '>')
+        throw new Error('TODO Not implemented yet');
+
+    if (op === '&')
+        throw new Error('TODO Not implemented yet');
+
+    throw new Error(`Unknown built-in: ${op}`);
+}

src/main.ts

@@ -1,6 +1,6 @@
-// import { evaluate } from './interpreter'
+import { evaluate } from './interpreter'
 // import type { AST } from './ast'
-// import type { Env } from './env'
+import type { Env } from './env'
 import { tokenize } from './lexer'
 import { Parser } from './parser'
 import { prettyPrint } from './ast';
@@ -25,11 +25,12 @@ console.log(tokenize(str));
 // const tokens2 = tokenize("let x = (y) => 5 + y in x(3)");
 // const tokens2 = tokenize("let x = 5 in x * 4");
 // const tokens2 = tokenize("(x, y) => x + y");
-const tokens2 = tokenize('point { x = 3 }');
+// const tokens2 = tokenize('point { x = 3 }');
+// const tokens2 = tokenize('add1 = (x \\ x + 1); add1 3');
+const tokens2 = tokenize('sum = (x y \\ x + y); sum 5 3');
 const p2 = new Parser(tokens2);
 const ast3 = p2.parse();
 console.log(ast3);
 console.log(prettyPrint(ast3));
-// const env3: Env = new Map();
-// console.log(ast3);
-// console.log(evaluate(ast3, env3));
+const env3: Env = new Map();
+console.log(evaluate(ast3, env3));

src/types.ts

@@ -16,11 +16,6 @@ export type StringValue = {
     value: string
 }
 
-export type BoolValue = {
-    kind: 'bool'
-    value: boolean
-}
-
 export type Closure = {
     kind: 'closure'
     params: string[]
@@ -28,4 +23,20 @@ export type Closure = {
     env: Env
 }
 
-export type Value = IntValue | FloatValue | StringValue | BoolValue | Closure;
+export type ListValue = {
+    kind: 'list'
+    elements: Value[]
+}
+
+export type RecordValue = {
+    kind: 'record'
+    fields: { [key: string]: Value }
+}
+
+export type ConstructorValue = {
+    kind: 'constructor'
+    name: string
+    args: Value[]
+}
+
+export type Value = IntValue | FloatValue | StringValue | Closure | ListValue | RecordValue | ConstructorValue;