1 files changed, 11 insertions, 1 deletions
diff --git a/module/util.scm b/module/util.scm
index 89f6dab6..707cba90 100644
--- a/module/util.scm
+++ b/module/util.scm
@@ -11,7 +11,7 @@
                 quote?
                 re-export-modules
                 use-modules*
-                -> set
+                -> set aif
                 tree-map let-lazy)
   #:replace (let* set! define-syntax
                   when unless if))
@@ -44,6 +44,13 @@
     ((@ (guile) if) p t
      (begin f ...))]))
 
+(define-syntax aif
+  (lambda (stx)
+    (syntax-case stx ()
+      [(_ condition true-clause false-clause)
+       (with-syntax ((it (datum->syntax stx 'it)))
+         #'(let ((it condition))
+             (if it true-clause false-clause)))])))
 
 
 (define-public upstring->symbol (compose string->symbol string-upcase))
@@ -356,6 +363,9 @@
      (-> (func obj) rest ...)]))
 
 
+;; Non-destructive set, syntax extension from set-fields from (srfi
+;; srfi-9 gnu). Also doubles as a non-destructive mod!, if the `='
+;; operator is used.
 (define-syntax set
   (syntax-rules (=)
     [(set (acc obj)  value)