Ignore outputs of side-effecting, element-handler functions.

[hope.git] / src / hope_option.erl

diff --git a/src/hope_option.erl b/src/hope_option.erl
index 7a87438..c645c53 100644 (file)
--- a/src/hope_option.erl
+++ b/src/hope_option.erl
@@ -7,15 +7,19 @@
     ]).
 
 -export(
-    [ put/2
-    , get/2
-    , return/1
-    , return/2
+    % Generic monad interface
+    [ return/1
     , map/2
-    , iter/2
     , pipe/2
+
+    % Specific to hope_option:t()
+    , return/2
+    , put/2
+    , get/2
+    , iter/2
     , of_result/1
     , of_undefined/1
+    , validate/2
     ]).
 
 
@@ -53,10 +57,13 @@ return(X, Condition) ->
 map({some, X}, F) -> {some, F(X)};
 map(none     , _) -> none.
 
--spec iter(t(A), fun((A) -> (ok))) ->
+-spec iter(t(A), fun((A) -> (any()))) ->
+    ok.
+iter({some, X}, F) ->
+    _ = F(X),
+    ok;
+iter(none, _) ->
     ok.
-iter({some, X}, F) -> ok = F(X);
-iter(none     , _) -> ok.
 
 -spec pipe([fun((A) -> t(B))], A) ->
     t(B).
@@ -77,3 +84,13 @@ of_result({error, _}) -> none.
     t(A).
 of_undefined(undefined) -> none;
 of_undefined(X)         -> {some, X}.
+
+-spec validate(t(A), fun((A) -> boolean())) ->
+    t(A).
+validate(none, _) ->
+    none;
+validate({some, X}=T, F) ->
+    case F(X)
+    of  false -> none
+    ;   true  -> T
+    end.