Add field appenders.

* ccwl/ccwl.scm (field-appender, append-step-in, append-step-out,
append-command-inputs, append-command-outputs): New functions.

1 files changed, 16 insertions, 0 deletions

diff --git a/ccwl/ccwl.scm b/ccwl/ccwl.scm
index e73b9e6..0eed492 100644
--- a/ccwl/ccwl.scm
+++ b/ccwl/ccwl.scm
@@ -127,6 +127,16 @@
   (in step-in set-step-in)
   (out step-out set-step-out))
 
+(define (field-appender getter setter)
+  (lambda (object element)
+    (setter object (cons element (getter object)))))
+
+(define append-step-in
+  (field-appender step-in set-step-in))
+
+(define append-step-out
+  (field-appender step-out set-step-out))
+
 (define-immutable-record-type <command>
   (make-command inputs outputs args stdin other)
   command?
@@ -136,6 +146,12 @@
   (stdin command-stdin set-command-stdin)
   (other command-other))
 
+(define append-command-inputs
+  (field-appender command-inputs set-command-inputs))
+
+(define append-command-outputs
+  (field-appender command-outputs set-command-outputs))
+
 (define* (command id arguments #:key (additional-inputs '()) (outputs '()) (other '()))
   (make-step id
              (make-command (append (filter input? arguments)