From 470d14d6df3b604ade8369415ae28bc9fbf2a38e Mon Sep 17 00:00:00 2001
From: Sameer Rahmani <lxsameer@gnu.org>
Date: Wed, 1 Jan 2020 17:44:19 +0000
Subject: [PATCH] Cond special form has been added

---
 .../java/serene/simple/CondSpecialForm.java   | 53 +++++++++++++++++++
 src/main/java/serene/simple/SpecialForm.java  |  3 ++
 2 files changed, 56 insertions(+)
 create mode 100644 src/main/java/serene/simple/CondSpecialForm.java

diff --git a/src/main/java/serene/simple/CondSpecialForm.java b/src/main/java/serene/simple/CondSpecialForm.java
new file mode 100644
index 0000000..38bf319
--- /dev/null
+++ b/src/main/java/serene/simple/CondSpecialForm.java
@@ -0,0 +1,53 @@
+/**
+ * Serene (simple) - A PoC lisp to collect data on Serenes concepts
+ * Copyright (C) 2019-2020 Sameer Rahmani <lxsameer@gnu.org>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA  02110-1301, USA.
+ */
+package serene.simple;
+
+public class CondSpecialForm extends SpecialForm {
+
+  private ListNode<Node> conditions;
+
+  public CondSpecialForm(ListNode<Node> listNode) {
+    super(listNode);
+
+    if (!(listNode.rest().first() instanceof ListNode)) {
+      throw new SereneException("Let bindings should be a list of pairs.");
+    }
+
+    this.conditions = (ListNode<Node>) listNode.rest().first();
+  }
+
+  @Override
+  public Object eval(IScope scope) {
+    for (Object x : this.conditions) {
+      if (!(x instanceof ListNode))
+        throw new SereneException(
+          String.format("Expect a pair instead of '%s' for 'cond'.",
+                        x.toString()));
+
+      Object pred = ((ListNode<Node>) x).first().eval(scope);
+
+      if (pred != null && pred != Boolean.FALSE) {
+        return ((ListNode<Node>) x).rest().first().eval(scope);
+      }
+    }
+
+    return null;
+  }
+}
diff --git a/src/main/java/serene/simple/SpecialForm.java b/src/main/java/serene/simple/SpecialForm.java
index 3bf3dcb..1cce013 100644
--- a/src/main/java/serene/simple/SpecialForm.java
+++ b/src/main/java/serene/simple/SpecialForm.java
@@ -26,6 +26,7 @@ public class SpecialForm extends Node {
   private static final SymbolNode IF = new SymbolNode("if");
   private static final SymbolNode QUOTE = new SymbolNode("quote");
   private static final SymbolNode LET = new SymbolNode("let");
+  private static final SymbolNode COND = new SymbolNode("cond");
 
   public ListNode<Node> node;
 
@@ -42,6 +43,8 @@ public class SpecialForm extends Node {
       return new DefSpecialForm(l);
     } else if (l.first().equals(LET)){
       return new LetSpecialForm(l);
+    } else if (l.first().equals(COND)){
+      return new CondSpecialForm(l);
     } else if (l.first().equals(FN)) {
       return new FnSpecialForm(l);
     } else if (l.first().equals(IF)) {