From 175e8abf1bae04e78103ea9e43d0d246a57c39f6 Mon Sep 17 00:00:00 2001
From: Jordan Orelli <jordanorelli@gmail.com>
Date: Sun, 21 Oct 2012 13:25:34 -0400
Subject: [PATCH] added "begin" special form

---
 input.scm  | 10 ++++++++++
 skeam.go   |  1 +
 special.go | 15 +++++++++++++++
 3 files changed, 26 insertions(+)

diff --git a/input.scm b/input.scm
index 5f979a5..31150b3 100644
--- a/input.scm
+++ b/input.scm
@@ -42,3 +42,13 @@ x
 (plusone 1)
 
 ((lambda (x) (* x x)) 4)
+
+((lambda (x y) (+ x y)) 10 25)
+
+(define make-account
+  (lambda (balance)
+    (lambda (amt)
+      (begin (set! balance (+ balance amt)) balance))))
+
+(define a1 (make-account 100.00))
+(a1 -20.00)
diff --git a/skeam.go b/skeam.go
index f3290a5..324256b 100644
--- a/skeam.go
+++ b/skeam.go
@@ -32,6 +32,7 @@ var universe = &environment{map[symbol]interface{}{
 	"if":     special(_if),
 	"set!":   special(set),
 	"lambda": special(mklambda),
+	"begin":  special(begin),
 }, nil}
 
 // parses the string lexeme into a value that can be eval'd
diff --git a/special.go b/special.go
index 412fef5..efdbb19 100644
--- a/special.go
+++ b/special.go
@@ -187,3 +187,18 @@ func mklambda(env *environment, args ...interface{}) (interface{}, error) {
 
 	return lambda{env, arglabels, body}, nil
 }
+
+func begin(env *environment, args ...interface{}) (interface{}, error) {
+	debugPrint("begin")
+
+	var err error
+	var v interface{}
+	for _, arg := range args {
+		v, err = eval(arg, env)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	return v, nil
+}