From 249061982f6e23bfa7eb48ce3eb4f9f568f0d75e Mon Sep 17 00:00:00 2001
From: Yuichi Nishiwaki <yuichi.nishiwaki@gmail.com>
Date: Thu, 14 Nov 2013 16:52:10 +0900
Subject: [PATCH] =?UTF-8?q?add=20symbol=3D=3F=20function?=

---
 README.md           |  2 +-
 piclib/built-in.scm | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index 3cbdc42c..ab481020 100644
--- a/README.md
+++ b/README.md
@@ -67,7 +67,7 @@
 | 6.2.7 Numerical input and output | no | |
 | 6.3 Booleans | yes | |
 | 6.4 Pairs and lists | yes | |
-| 6.5 Symbols | incomplete | TODO: `symbol=?`, `symbol->string`, `string->symbol` |
+| 6.5 Symbols | yes | |
 | 6.6 Characters | incomplete | TODO: almost all functions in the section :-( |
 | 6.7 Strings | incomplete | |
 | 6.8 Vectors | incomplete | TODO: `vector-copy`, ...etc |
diff --git a/piclib/built-in.scm b/piclib/built-in.scm
index e98b043b..9eea4614 100644
--- a/piclib/built-in.scm
+++ b/piclib/built-in.scm
@@ -254,3 +254,19 @@
 	    #f)))
   (or (every (lambda (x) (eq? x #t)) objs)
       (every (lambda (x) (eq? x #f)) objs)))
+
+
+(define (symbol=? . objs)
+  (define (every pred list)
+    (if (null? list)
+	#t
+	(if (pred (car list))
+	    (every pred (cdr list))
+	    #f)))
+  (let ((sym (car objs)))
+    (if (symbol? sym)
+	(every (lambda (x)
+		 (and (symbol? x)
+		      (eq? x sym)))
+	       (cdr objs))
+	#f)))