added repl

Author: igorw

repl.php

@@ -0,0 +1,46 @@
+<?php
+
+namespace igorw\lambda;
+
+use Symfony\Component\Debug\ErrorHandler;
+
+require 'vendor/autoload.php';
+
+function prompt($mode) {
+    echo "$mode> ";
+
+    return true;
+}
+
+function format($result) {
+    if (is_bool($result)) {
+        return json_encode($result);
+    }
+
+    return $result;
+}
+
+$mode = 'i';
+
+while (prompt($mode) && false !== ($line = fgets(STDIN))) {
+    $exp = trim($line);
+
+    if (in_array($exp, ['i', 'b'], true)) {
+        $mode = $exp;
+        continue;
+    }
+
+    $factories = [
+        'i' => 'igorw\lambda\to_int',
+        'b' => 'igorw\lambda\to_bool',
+    ];
+
+    try {
+        $factory = $factories[$mode];
+        echo format(evaluate($factory(parse($exp))))."\n";
+    } catch (\Exception $e) {
+        echo $e->getMessage()."\n";
+    }
+}
+
+echo "\n";