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digitalmars.D - A partial template application literal syntax

reply "bearophile" <bearophileHUGS lycos.com> writes:
 From this long Reddit post:
http://www.reddit.com/r/haskell/comments/zxcks/haskell_vs_f_vs_scala_a_highlevel_language/c68ybn1

I have seen this linked page:
https://github.com/non/kind-projector

Where it introduces a (fragile) Scala syntax like:
Tuple3[Int, ?, ?]

That is similar to this D, but it's usable in-place:
template IntFirst3(T2, T3) { alias Tuple!(int, T2, T3) IntFirst3; 
}

A comparable hypothetical D syntax, for partial template 
application:
Tuple!(int, ?, ?)

Being it usable in-place, you can use it as:

static asssert(is(Tuple!(int, ?, ?)!(double, float) ==
                   Tuple!(int, double, float)));

It's a fun syntax: Foo!?

Bye,
bearophile
Sep 17 2012
next sibling parent Timon Gehr <timon.gehr gmx.ch> writes:
On 09/17/2012 03:53 PM, bearophile wrote:
  From this long Reddit post:
 http://www.reddit.com/r/haskell/comments/zxcks/haskell_vs_f_vs_scala_a_highlevel_language/c68ybn1


 I have seen this linked page:
 https://github.com/non/kind-projector

 Where it introduces a (fragile) Scala syntax like:
 Tuple3[Int, ?, ?]

Eiffel uses this for partial method application. http://archive.eiffel.com/doc/online/eiffel50/intro/language/tutorial-12.html
 That is similar to this D, but it's usable in-place:
 template IntFirst3(T2, T3) { alias Tuple!(int, T2, T3) IntFirst3; }

 A comparable hypothetical D syntax, for partial template application:
 Tuple!(int, ?, ?)

 Being it usable in-place, you can use it as:

 static asssert(is(Tuple!(int, ?, ?)!(double, float) ==
                    Tuple!(int, double, float)));

You cannot because multiple ! arguments are disallowed. Parentheses do not help either because DMDs parser will interpret it as a deprecated C-style cast expression. (unless this is removed, the claim that binary '!' makes parsing non-ambiguous is a myth.)
 It's a fun syntax: Foo!?

 Bye,
 bearophile

Sep 17 2012
prev sibling next sibling parent reply Denis Shelomovskij <verylonglogin.reg gmail.com> writes:
17.09.2012 17:53, bearophile пишет:
  From this long Reddit post:
 http://www.reddit.com/r/haskell/comments/zxcks/haskell_vs_f_vs_scala_a_highlevel_language/c68ybn1


 I have seen this linked page:
 https://github.com/non/kind-projector

 Where it introduces a (fragile) Scala syntax like:
 Tuple3[Int, ?, ?]

 That is similar to this D, but it's usable in-place:
 template IntFirst3(T2, T3) { alias Tuple!(int, T2, T3) IntFirst3; }

 A comparable hypothetical D syntax, for partial template application:
 Tuple!(int, ?, ?)

 Being it usable in-place, you can use it as:

 static asssert(is(Tuple!(int, ?, ?)!(double, float) ==
                    Tuple!(int, double, float)));

 It's a fun syntax: Foo!?

 Bye,
 bearophile

Just want to mention about existent (and more flexible than this syntax) library solution. Search for `Bind` here: https://bitbucket.org/denis_sh/misc/src/tip/stdd/typetuple.d -- Денис В. Шеломовский Denis V. Shelomovskij
Sep 17 2012
parent Denis Shelomovskij <verylonglogin.reg gmail.com> writes:
18.09.2012 1:56, bearophile пишет:
 Denis Shelomovskij:

 Just want to mention about existent (and more flexible than this
 syntax) library solution.
 Search for `Bind` here:
 https://bitbucket.org/denis_sh/misc/src/tip/stdd/typetuple.d

Its ddocs show this: import std.traits; static assert(is(staticBind!(CommonType, long, allArgs).Res!int == long)); static assert(!staticBind!(isImplicitlyConvertible, arg!0, int).Res!long); static assert( staticBind!(isImplicitlyConvertible, int , arg!0).Res!long); alias staticBind!(staticMap, Unqual, allArgs).Res UnqualAll; static assert(is(UnqualAll!(const(int), immutable(bool[])) T) && T.length == 2 && is(T[0] == int) && is(T[1] == immutable(bool)[])); I have understood the meaning and usage of those "type lambdas" that use ? in Scala as soon I have seen them, while I don't get much from this noisy stuff :-( Bye, bearophile

Yes, my library solution is rather ugly (but still doesn't know why it isn't as obvious as Scala's one). Just added a clearer one (if somebody needs this). Search for "Binds template arguments using format string." (second `Bind` template) here (if you want): https://bitbucket.org/denis_sh/misc/src/tip/stdd/typetuple.d To conclude: Your proposal: alias Tuple!(int, ?, ?) T; My first solution: alias staticBind!(Tuple, int, arg!0, arg!1).Res T; My second solution: mixin Bind!q{ Tuple!(int, %0, %1) T }; From docs: Binds template arguments using format string. Example: ---- import std.traits; mixin Bind!q{ CommonType!(long, %*) CommonTypeToLong }; static assert(is(CommonTypeToLong!int == long)); mixin Bind!q{ isImplicitlyConvertible!(%0, int) isImplicitlyConvertibleToInt }; static assert(!isImplicitlyConvertibleToInt!long); mixin Bind!q{ isImplicitlyConvertible!(int, %0) isImplicitlyConvertibleFromInt }; static assert( isImplicitlyConvertibleFromInt!long); mixin Bind!q{ staticMap!(Unqual, %*) UnqualAll }; static assert(is(UnqualAll!(const(int), immutable(bool[])) T) && T.length == 2 && is(T[0] == int) && is(T[1] == immutable(bool)[])); -- Денис В. Шеломовский Denis V. Shelomovskij
Sep 24 2012
prev sibling parent "bearophile" <bearophileHUGS lycos.com> writes:
Denis Shelomovskij:

 Just want to mention about existent (and more flexible than 
 this syntax) library solution.
 Search for `Bind` here:
 https://bitbucket.org/denis_sh/misc/src/tip/stdd/typetuple.d

Its ddocs show this: import std.traits; static assert(is(staticBind!(CommonType, long, allArgs).Res!int == long)); static assert(!staticBind!(isImplicitlyConvertible, arg!0, int).Res!long); static assert( staticBind!(isImplicitlyConvertible, int , arg!0).Res!long); alias staticBind!(staticMap, Unqual, allArgs).Res UnqualAll; static assert(is(UnqualAll!(const(int), immutable(bool[])) T) && T.length == 2 && is(T[0] == int) && is(T[1] == immutable(bool)[])); I have understood the meaning and usage of those "type lambdas" that use ? in Scala as soon I have seen them, while I don't get much from this noisy stuff :-( Bye, bearophile
Sep 17 2012