signal: Run newly added hooks immediately.

* sly/signal.scm (add-signal-hook!): Apply 'proc' immediately.

1 files changed, 6 insertions, 2 deletions

diff --git a/sly/signal.scm b/sly/signal.scm
index a35f042..5bd9a29 100644
--- a/sly/signal.scm
+++ b/sly/signal.scm
@@ -116,8 +116,12 @@ procedure PROC, and a list of INPUTS."
 (define (add-signal-hook! signal proc)
   "Add PROC, a procedure that accepts a single argument, to the hook
 associated with SIGNAL.  When SIGNAL receives a new value, PROC will
-be applied with that value."
-  (add-hook! (signal-hook (signal-unbox signal)) proc))
+be applied with that value.  PROC will automatically be called once
+after registering it to run the hook with the current value of
+SIGNAL."
+  (add-hook! (signal-hook (signal-unbox signal)) proc)
+  ;; Run the initial hook.
+  (proc (signal-ref signal)))
 
 (define (remove-signal-hook! signal proc)
   "Remove the procedure PROC from the hook associated with SIGNAL."