Predicate wrapper

2 files changed, 12 insertions, 0 deletions

diff --git a/tests/struct.scm b/tests/struct.scm
index 64f4137..dcc6770 100644
--- a/tests/struct.scm
+++ b/tests/struct.scm
@@ -24,6 +24,13 @@
         (test-eqv 5 x)
         (test-eqv 15 y)))))
 
+(test-group "instance-of?"
+  (define-struct <animal> species)
+  (define-struct <dog> breed)
+  (let ((my-dog (make-struct <dog> "Labrador")))
+    (test-assert (instance-of? <dog> my-dog))
+    (test-assert (not (instance-of? <animal> my-dog)))))
+
 (test-group "error-handling"
   (define-struct <empty>)
   (test-error #t (make-struct <empty> 1)))
diff --git a/weeb/struct.scm b/weeb/struct.scm
index 64349ef..65fa2ab 100644
--- a/weeb/struct.scm
+++ b/weeb/struct.scm
@@ -20,6 +20,7 @@
   #:use-module (ice-9 regex)
   #:export (define-struct
             make-struct
+            instance-of?
             with-accessors
             call-with-slots))
 
@@ -40,6 +41,10 @@
 instantiate the record's fields."
   (apply (record-constructor type) args))
 
+(define (instance-of? type rtd)
+  "Returns true if RTD is an instance of TYPE."
+  ((record-predicate type) rtd))
+
 ;; Bind the accessors for the fields of the record RTD to local
 ;; variables in BODY. RTD must be a record type descriptor.
 (define-syntax with-accessors