From 0a8c190d0025612b5e25cb2dc4910a9b1ae280b6 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Alejandro=20G=C3=B3mez?= <alejandro@dialelo.com>
Date: Sat, 15 Aug 2015 12:37:19 +0200
Subject: [PATCH] WIP: applicative instance for maybe transformer
---
src/cats/monad/maybe.cljc | 19 +++++++++++++++++++
test/cats/monad/maybe_spec.cljc | 12 ++++++++++++
2 files changed, 31 insertions(+)
diff --git a/src/cats/monad/maybe.cljc b/src/cats/monad/maybe.cljc
index 8251f49..08e1305 100644
--- a/src/cats/monad/maybe.cljc
+++ b/src/cats/monad/maybe.cljc
@@ -235,6 +235,25 @@
#(p/fmap maybe-monad f %)
fv))
+ p/Applicative
+ (pure [_ v]
+ (p/mreturn inner-monad (just v)))
+
+ (fapply [_ af av]
+ (p/mbind inner-monad
+ af
+ (fn [mf]
+ (p/mbind maybe-monad
+ mf
+ (fn [f]
+ (p/mbind inner-monad
+ av
+ (fn [mv]
+ (p/mbind maybe-monad
+ mv
+ (fn [v]
+ (p/mreturn inner-monad (just (f v))))))))))))
+
p/Monad
(mreturn [m v]
(p/mreturn inner-monad (just v)))
diff --git a/test/cats/monad/maybe_spec.cljc b/test/cats/monad/maybe_spec.cljc
index 622f1f5..f490a8a 100644
--- a/test/cats/monad/maybe_spec.cljc
+++ b/test/cats/monad/maybe_spec.cljc
@@ -72,6 +72,18 @@
(m/with-monad maybe-vector-transformer
(m/return 2))))
+ (t/is (= [(maybe/just 42)]
+ (m/with-monad maybe-vector-transformer
+ (m/fapply [(maybe/just inc)] [(maybe/just 41)]))))
+
+ (t/is (= [(maybe/just 42)
+ (maybe/just 99)
+ (maybe/just "41")
+ (maybe/just "98")]
+ (m/with-monad maybe-vector-transformer
+ (m/fapply [(maybe/just inc) (maybe/just str)]
+ [(maybe/just 41) (maybe/just 98)]))))
+
(t/is (= [(maybe/just 1)
(maybe/just 2)
(maybe/just 2)