change case to cond

README.md

@@ -279,8 +279,8 @@ This allows for some fun tricks. For example, we can retrieve the body of a func
 Name  | Safe-mode | Example | Example result | Description
 ----- | --------- | ------- | -------------- | -----------
 and   | yes | `(and 1 0 2)` | `0` | Return the first value that evaluates to false, or the last value.
-case  | yes | `(case (= 1 0) 0 (= 1 1) 1)` | `1` | Treat odd arguments as tests and even arguments as values. Evaluate and return the value after the first test that evaluates to true.
+cond  | yes | `(cond [(= 0 1) 0] [(= 1 1) (print "1") 1])` | `11` | Treat first item of each argument as test. If test evaluates to true, evaluate the following expressions and return the value of the last.
-      | yes | `(case (= 1 0) 0 "no match")` | `"no match"` | You can also give optional last argument to case which is returned if none of the tests evaluated to true.
+      | yes | `(cond [(= 0 1) 0] [(= 1 2) 1] [else 3])` | `3` | The symbol `else` evaluates to true. It can be used as the last condition in case no previous test evaluates to true.
 def   | yes | `(def addOne (fn (a) (+ a 1)))` | `<function>` | Define a value in the current environment.
 do    | yes | `(do (print 1) 2)` | `12` | Evaluate multiple expressions and return the value of the last.
 env   | yes | `(env +)` | `<function>` | Return a definition from the current environment represented by argument. Without arguments return the current environment as a hash-map.

src/Evaller.php

@@ -93,26 +93,42 @@ class Evaller
 
                     $ast = $astData[$astLength - 1];
                     continue; // tco
-                } elseif ($symbolName == 'case') {
+                } elseif ($symbolName == 'cond') {
                     if ($astLength < 2) {
-                        throw new MadLispException("case requires at least 1 argument");
+                        throw new MadLispException("cond requires at least 1 argument");
+                    }
+
+                    for ($i = 1; $i < $astLength; $i++) {
+                        if (!($astData[$i] instanceof Seq)) {
+                            throw new MadLispException("argument to cond is not seq");
+                        }
+
+                        $condData = $astData[$i]->getData();
+
+                        if (count($condData) < 2) {
+                            throw new MadLispException("clause for cond requires at least 2 arguments");
+                        }
+
+                        if ($condData[0] instanceof Symbol && $condData[0]->getName() == 'else') {
+                            $test = true;
+                        } else {
+                            $test = $this->eval($condData[0], $env, $depth + 1);
                         }
 
-                    for ($i = 1; $i < $astLength - 1; $i += 2) {
-                        $test = $this->eval($astData[$i], $env, $depth + 1);
                         if ($test == true) {
-                            $ast = $astData[$i + 1];
+                            // Evaluate interval expressions
+                            for ($a = 1; $a < count($condData) - 1; $a++) {
+                                $this->eval($condData[$a], $env, $depth + 1);
+                            }
+
+                            // Evaluate last expression
+                            $ast = $condData[count($condData) - 1];
                             continue 2; // tco
                         }
                     }
 
-                    // Last value, no test
+                    // No matches
-                    if ($astLength % 2 == 0) {
-                        $ast = $astData[$astLength - 1];
-                        continue; // tco
-                    } else {
                     return null;
-                    }
                 } elseif ($symbolName == 'def') {
                     if ($astLength != 3) {
                         throw new MadLispException("def requires exactly 2 arguments");