From: Tim Vaughan <tgvaughan@gmail.com>
Date: Sun, 6 Nov 2016 05:06:06 +0000 (+1300)
Subject: Implemented and and or as macros.
X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=commitdiff_plain;h=749dd8439730c404058c7a672252ab19967268ac;p=scheme.forth.jl.git

Implemented and and or as macros.
---

diff --git a/scheme-library.scm b/scheme-library.scm
index ffe02ea..aad91f4 100644
--- a/scheme-library.scm
+++ b/scheme-library.scm
@@ -87,6 +87,35 @@
                 (error "cond requires at least one clause.")
                 (expand-clauses clauses)))
 
+; and
+
+(define (expand-and-expressions expressions)
+  (if (null? expressions)
+    #t
+    (let ((first (car expressions))
+          (rest (cdr expressions)))
+      `(if ,first
+         ,(expand-and-expressions rest)
+         #f))))
+
+(define-macro (and . expressions)
+              (expand-and-expressions expressions))
+
+; or
+
+(define (expand-or-expressions expressions)
+  (if (null? expressions)
+    #f
+    (let ((first (car expressions))
+          (rest (cdr expressions)))
+      `(if ,first
+         #t
+         ,(expand-or-expressions rest)))))
+
+(define-macro (or . expressions)
+              (expand-or-expressions expressions))
+
+
 ;; TESTING
 
 (define-macro (backwards . body)