X-Git-Url: https://git.xandkar.net/?a=blobdiff_plain;f=src%2Fhope_option.erl;h=996e3428eeac2cb66a2f4005745352a5fdd6d374;hb=352ddeb475ab48aabfab59558827e0e8d927551f;hp=c461d04d1b70d3bbd292e954aa21c55eb4921c5e;hpb=ed9905af6fa1dba6f89759d6dbfc970426122bde;p=hope.git

diff --git a/src/hope_option.erl b/src/hope_option.erl
index c461d04..996e342 100644
--- a/src/hope_option.erl
+++ b/src/hope_option.erl
@@ -1,14 +1,25 @@
 -module(hope_option).
 
+-behavior(hope_gen_monad).
 
 -export_type(
     [ t/1
     ]).
 
 -export(
-    [ put/2
-    , get/2
+    % Generic monad interface
+    [ return/1
     , map/2
+    , pipe/2
+
+    % Specific to hope_option:t()
+    , return/2
+    , put/2
+    , get/2
+    , iter/2
+    , of_result/1
+    , of_undefined/1
+    , validate/2
     ]).
 
 
@@ -21,17 +32,62 @@
 -spec put(A, fun((A) -> boolean())) ->
     t(A).
 put(X, F) ->
-    case F(X)
-    of  true  -> {some, X}
-    ;   false -> none
-    end.
+    return(X, F).
 
 -spec get(t(A), Default :: A) ->
     A.
 get({some, X}, _) -> X;
 get(none     , Y) -> Y.
 
+-spec return(A) ->
+    {some, A}.
+return(X) ->
+    {some, X}.
+
+-spec return(A, fun((A) -> boolean())) ->
+    t(A).
+return(X, Condition) ->
+    case Condition(X)
+    of  true  -> {some, X}
+    ;   false -> none
+    end.
+
 -spec map(t(A), fun((A) -> (B))) ->
     t(B).
 map({some, X}, F) -> {some, F(X)};
 map(none     , _) -> none.
+
+-spec iter(t(A), fun((A) -> (ok))) ->
+    ok.
+iter({some, X}, F) -> ok = F(X);
+iter(none     , _) -> ok.
+
+-spec pipe([fun((A) -> t(B))], A) ->
+    t(B).
+pipe([], X) ->
+    return(X);
+pipe([F|Fs], X) ->
+    case F(X)
+    of  none      -> none
+    ;   {some, Y} -> pipe(Fs, Y)
+    end.
+
+-spec of_result(hope_result:t(A, _B)) ->
+    t(A).
+of_result({ok, X})    -> {some, X};
+of_result({error, _}) -> none.
+
+-spec of_undefined(undefined | A) ->
+    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.