X-Git-Url: https://thelambdalab.xyz/gitweb/index.cgi?a=blobdiff_plain;f=scheme-library.scm;h=f95ed65595fc71e5cf24ef5ef4edf492ad8e1d63;hb=a95efe1cb2d3774471bb9c0fe4628abe09032ca6;hp=ffe02ea14b441741b8b4b90a98dc6f01a40e4e30;hpb=1d07170e70db6f42a900ea918ac22cce65345f2f;p=scheme.forth.jl.git

diff --git a/scheme-library.scm b/scheme-library.scm
index ffe02ea..f95ed65 100644
--- a/scheme-library.scm
+++ b/scheme-library.scm
@@ -87,6 +87,39 @@
                 (error "cond requires at least one clause.")
                 (expand-clauses clauses)))
 
+; and
+
+(define (expand-and-expressions expressions)
+  (let ((first (car expressions))
+        (rest (cdr expressions)))
+    (if (null? rest)
+      first
+      `(if ,first
+         ,(expand-and-expressions rest)
+         #f))))
+
+(define-macro (and . expressions)
+              (if (null? expressions)
+                #t
+                (expand-and-expressions expressions)))
+
+; or
+
+(define (expand-or-expressions expressions)
+  (if (null? expressions)
+    #f
+    (let ((first (car expressions))
+          (rest (cdr expressions))
+          (val (gensym)))
+      `(let ((,val ,first))
+         (if ,val
+            ,val
+            ,(expand-or-expressions rest))))))
+
+(define-macro (or . expressions)
+              (expand-or-expressions expressions))
+
+
 ;; TESTING
 
 (define-macro (backwards . body)