From e5d8a44ca864e52b25cdeb52ea2ec71d211f8bf4 Mon Sep 17 00:00:00 2001
From: Sameer Rahmani <lxsameer@gnu.org>
Date: Fri, 3 Jan 2020 00:03:56 +0000
Subject: [PATCH] Native reduce function has been added

---
 benchmarks/fib.srns                           |  2 +-
 src/main/java/serene/simple/RootScope.java    |  1 +
 .../java/serene/simple/builtin/ReduceFn.java  | 65 +++++++++++++++++++
 3 files changed, 67 insertions(+), 1 deletion(-)
 create mode 100644 src/main/java/serene/simple/builtin/ReduceFn.java

diff --git a/benchmarks/fib.srns b/benchmarks/fib.srns
index 90ea927..dded7cd 100644
--- a/benchmarks/fib.srns
+++ b/benchmarks/fib.srns
@@ -1,4 +1,4 @@
-(def reduce
+(def reduce1
      (fn (f xs initial-value)
          (cond
           ((first xs) (reduce f (rest xs) (f initial-value (first xs))))
diff --git a/src/main/java/serene/simple/RootScope.java b/src/main/java/serene/simple/RootScope.java
index 2a203d9..a8198f7 100644
--- a/src/main/java/serene/simple/RootScope.java
+++ b/src/main/java/serene/simple/RootScope.java
@@ -51,6 +51,7 @@ public class RootScope extends AScope {
       put("first", new FirstFn());
       put("rest", new RestFn());
       put("doc", new DocFn());
+      put("reduce", new ReduceFn());
       put("System", System.class);
       put("Boolean", Boolean.class);
       put("String", String.class);
diff --git a/src/main/java/serene/simple/builtin/ReduceFn.java b/src/main/java/serene/simple/builtin/ReduceFn.java
new file mode 100644
index 0000000..f7039a6
--- /dev/null
+++ b/src/main/java/serene/simple/builtin/ReduceFn.java
@@ -0,0 +1,65 @@
+/**
+ * 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.builtin;
+
+import java.util.List;
+import java.util.function.Function;
+
+import serene.simple.IDoc;
+import serene.simple.IScope;
+import serene.simple.ListNode;
+import serene.simple.SereneException;
+
+
+public class ReduceFn extends AFn implements IDoc {
+  public String fnName() {
+    return "reduce";
+  };
+
+  public String getDoc() {
+    return "(reduce f coll initial-value): Reduce the COLL by applying F.";
+  }
+
+  public Object eval(IScope scope) throws SereneException{
+    List<Object> args = this.arguments();
+
+    if (args.size() != 3) {
+      throw new SereneException(
+        String.format("reduce expects 3 parameters. Got %s", args.size()));
+    }
+
+    Function<Object,Object> fn = (Function<Object, Object>) args.get(0);
+    ListNode<Object> coll = (ListNode<Object>) args.get(1);
+    Object initialValue = args.get(2);
+
+    while(true) {
+      Object x = coll.first();
+
+      if (x == null)
+        break;
+
+      Object[] fnArgs = { initialValue, x };
+      coll = coll.rest();
+      initialValue = fn.apply(fnArgs);
+    }
+
+    return initialValue;
+  }
+}