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Followup to addition of apply #6390

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Merged
dlang-bot merged 2 commits into from
Mar 31, 2018
Merged

Followup to addition of apply #6390

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fb73b62
Followup to addition of apply
andralex Mar 30, 2018
abdce33
Update typecons.d
andralex Mar 30, 2018
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13 changes: 7 additions & 6 deletions std/typecons.d
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Original file line number Diff line number Diff line change
Expand Up @@ -3441,28 +3441,29 @@ if (is (typeof(nullValue) == T))
assert(ntts.to!string() == "2.5");
}

// apply
/**
Unpacks the content of a $(D Nullable), performs an operation and packs it again. Does nothing if isNull.

When called on a $(D Nullable), $(D apply) will unpack the value contained in the $(D Nullable),
pass it to the function you provide and wrap the result in another $(D Nullable) (if necessary).
If the Nullable is null, $(D apply) will return null itself.
When called on a `Nullable`, `apply` will unpack the value contained in the `Nullable`,
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@wilzbach wilzbach Mar 30, 2018 •
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I think we should continue the automation alternative here. At the moment we only converted std.algorithm automatically (see #5970)

-> #6391

pass it to the function you provide and wrap the result in another `Nullable` (if necessary).
If the `Nullable` is null, `apply` will return null itself.

Params:
t = a $(D Nullable)
t = a `Nullable`
fun = a function operating on the content of the nullable

Returns:
`fun(t.get).nullable` if `!t.isNull`, else `Nullable.init`.

See also:
$(HTTP en.wikipedia.org/wiki/Monad_(functional_programming)#The_Maybe_monad, The `Maybe` monad)
$(HTTPS en.wikipedia.org/wiki/Monad_(functional_programming)#The_Maybe_monad, The `Maybe` monad)
*/
template apply(alias fun)
{
import std.functional : unaryFun;

auto apply(T)(T t)
auto apply(T)(auto ref T t)
if (isInstanceOf!(Nullable, T) && is(typeof(unaryFun!fun(T.init.get))))
{
alias FunType = typeof(unaryFun!fun(T.init.get));
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