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| author | Hugo Hörnquist <hugo@lysator.liu.se> | 2018-11-16 00:53:15 +0100 |
|---|---|---|
| committer | Hugo Hörnquist <hugo@lysator.liu.se> | 2018-11-16 00:53:15 +0100 |
| commit | 3c96e1e1819d3fe68d5986cc8cb268e7698e0ab9 (patch) | |
| tree | fa5e59199f127b54e4f818c63d9d83efe574a400 | |
| parent | Add fmap instance for state monad. (diff) | |
| download | scheme-monad-3c96e1e1819d3fe68d5986cc8cb268e7698e0ab9.tar.gz scheme-monad-3c96e1e1819d3fe68d5986cc8cb268e7698e0ab9.tar.xz | |
Add instance of fmap for <optional>.
| -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)))) |