Re: Forwarding arguments through a std.algorithm.map
On Friday, 16 March 2018 at 20:39:33 UTC, Andrei Alexandrescu wrote: My knee-jerk reaction is that's a rather peculiar primitive to add to the standard library. -- Andrei I'm needing it for variadic equal...I'll put it as a private member in `equal`s template declaration for now.
Re: Forwarding arguments through a std.algorithm.map
On 03/16/2018 03:52 PM, Nordlöw wrote: On Saturday, 10 March 2018 at 21:31:41 UTC, ag0aep6g wrote: auto forwardMap(alias fun, Ts ...)(Ts things) { import std.meta: aliasSeqOf, staticMap; import std.range: iota; import std.typecons: Tuple; alias NewType(size_t i) = typeof(fun(things[i])); alias NewTypes = staticMap!(NewType, aliasSeqOf!(iota(things.length))); Tuple!NewTypes results; static foreach (i, thing; things) results[i] = fun(thing); return results; } Found a slightly compacter way without `iota` and `aliasSeqOf` and with (deprecated) string-lambda support and single-pass initialization using `= void` and `emplace`: /** Returns: `xs` forwarded through calls to `fun`. * * See also: https://forum.dlang.org/post/zjxmreegqkxgdzvih...@forum.dlang.org */ auto forwardMap(alias fun, Ts...)(Ts xs) { import std.meta : staticMap; alias MappedTypeOf(T) = typeof(fun(T.init)); alias NewTypes = staticMap!(MappedTypeOf, Ts); import std.typecons : Tuple; Tuple!NewTypes ys = void; import std.conv : emplace; import std.functional : unaryFun; alias fun_ = unaryFun!(fun); static foreach (immutable i, x; xs) { emplace([i], fun_(x)); } return ys; } I believe this should go into Phobos somewhere. Into std.typecons, std.meta or std.algorithm? My knee-jerk reaction is that's a rather peculiar primitive to add to the standard library. -- Andrei
Re: Forwarding arguments through a std.algorithm.map
On Saturday, 10 March 2018 at 21:31:41 UTC, ag0aep6g wrote: auto forwardMap(alias fun, Ts ...)(Ts things) { import std.meta: aliasSeqOf, staticMap; import std.range: iota; import std.typecons: Tuple; alias NewType(size_t i) = typeof(fun(things[i])); alias NewTypes = staticMap!(NewType, aliasSeqOf!(iota(things.length))); Tuple!NewTypes results; static foreach (i, thing; things) results[i] = fun(thing); return results; } Found a slightly compacter way without `iota` and `aliasSeqOf` and with (deprecated) string-lambda support and single-pass initialization using `= void` and `emplace`: /** Returns: `xs` forwarded through calls to `fun`. * * See also: https://forum.dlang.org/post/zjxmreegqkxgdzvih...@forum.dlang.org */ auto forwardMap(alias fun, Ts...)(Ts xs) { import std.meta : staticMap; alias MappedTypeOf(T) = typeof(fun(T.init)); alias NewTypes = staticMap!(MappedTypeOf, Ts); import std.typecons : Tuple; Tuple!NewTypes ys = void; import std.conv : emplace; import std.functional : unaryFun; alias fun_ = unaryFun!(fun); static foreach (immutable i, x; xs) { emplace([i], fun_(x)); } return ys; } I believe this should go into Phobos somewhere. Into std.typecons, std.meta or std.algorithm?
Re: Forwarding arguments through a std.algorithm.map
On Saturday, 10 March 2018 at 21:31:41 UTC, ag0aep6g wrote: Not tested beyond `f(1, 2.3, "foo")`: auto forwardMap(alias fun, Ts ...)(Ts things) { import std.meta: aliasSeqOf, staticMap; import std.range: iota; import std.typecons: Tuple; alias NewType(size_t i) = typeof(fun(things[i])); alias NewTypes = staticMap!(NewType, aliasSeqOf!(iota(things.length))); Tuple!NewTypes results; static foreach (i, thing; things) results[i] = fun(thing); return results; } Thanks! I'll try to put together something...
Re: Forwarding arguments through a std.algorithm.map
On Saturday, 10 March 2018 at 20:48:06 UTC, Nordlöw wrote: If I have a function bool f(Rs...)(Rs rs) is it somehow possible to map and forward all its arguments `rs` to another function bool g(Rs...)(Rs rs); through a call to some map-and-forward-like-function `forwardMap` in something like bool f(Rs...)(Rs rs) { alias someArbitraryFun = _ => _; return g(forwardMap!(someArbitraryFun)(rs)); } ? What should the definition of forwardMap look like? Does Phobos contain something like this already? there is staticMap.
Re: Forwarding arguments through a std.algorithm.map
On Saturday, 10 March 2018 at 20:48:06 UTC, Nordlöw wrote: If I have a function bool f(Rs...)(Rs rs) is it somehow possible to map and forward all its arguments `rs` to another function bool g(Rs...)(Rs rs); through a call to some map-and-forward-like-function `forwardMap` in something like bool f(Rs...)(Rs rs) { alias someArbitraryFun = _ => _; return g(forwardMap!(someArbitraryFun)(rs)); } ? What should the definition of forwardMap look like? Does Phobos contain something like this already? Not sure whether I understand what you are looking for, but std.functional is your friend here I think pipe/compose is the function you are searching for. https://dlang.org/phobos/std_functional.html#forward https://dlang.org/phobos/std_functional.html#partial https://dlang.org/phobos/std_functional.html#pipe
Re: Forwarding arguments through a std.algorithm.map
On Saturday, 10 March 2018 at 20:48:06 UTC, Nordlöw wrote: If I have a function bool f(Rs...)(Rs rs) is it somehow possible to map and forward all its arguments `rs` to another function bool g(Rs...)(Rs rs); docs: https://dlang.org/phobos/std_traits.html#.Parameters usage example: https://github.com/crimaniak/d-vision/blob/master/src/vision/eventbus.d#L173
Re: Forwarding arguments through a std.algorithm.map
On 03/10/2018 09:48 PM, Nordlöw wrote: If I have a function bool f(Rs...)(Rs rs) is it somehow possible to map and forward all its arguments `rs` to another function bool g(Rs...)(Rs rs); through a call to some map-and-forward-like-function `forwardMap` in something like bool f(Rs...)(Rs rs) { alias someArbitraryFun = _ => _; return g(forwardMap!(someArbitraryFun)(rs)); } ? Not with that syntax, as far as I know. A function can't return an alias seq like that. But it can return a std.typecons.Tuple. You'd have to add `.expand` then: return g(forwardMap!someArbitraryFun(rs).expand); What should the definition of forwardMap look like? Not tested beyond `f(1, 2.3, "foo")`: auto forwardMap(alias fun, Ts ...)(Ts things) { import std.meta: aliasSeqOf, staticMap; import std.range: iota; import std.typecons: Tuple; alias NewType(size_t i) = typeof(fun(things[i])); alias NewTypes = staticMap!(NewType, aliasSeqOf!(iota(things.length))); Tuple!NewTypes results; static foreach (i, thing; things) results[i] = fun(thing); return results; } I wouldn't call it "forwardMap". "tupleMap" or "seqMap" maybe? Does Phobos contain something like this already? Not that I know of.