diff options
| -rw-r--r-- | data/optional.scm | 9 |
1 files changed, 7 insertions, 2 deletions
diff --git a/data/optional.scm b/data/optional.scm index b008471..c90fec5 100644 --- a/data/optional.scm +++ b/data/optional.scm @@ -2,11 +2,11 @@ #:use-module (oop goops) #:use-module (ice-9 match) #:use-module (control monad) + #:use-module (data functor) #:export (nothing just nothing? just? return-optional) - ;; TODO is this reexport needed? - #:re-export (>>=)) + #:re-export (>>= >> fmap)) (define-class <optional> () (slot #:init-value #f @@ -47,3 +47,8 @@ (nothing? b)) (nothing) b)) + +(define-method (fmap (f <procedure>) + (m <optional>)) + (do x <- m + (return-optional (f x)))) |