View mode: basic / threaded / horizontal-split · Log in · Help
October 24, 2012
Re: Mixin replacement for switch...case?
Damn, I typed this a bit too fast. I forgot the imports:


> Probably, but my solution can be generalized further, to provide a
> sort of pattern-matching:

Add:

import std.conv;
import std.stdio;

> template match(cases...)
> {
>     auto match(Input...)(Input input)
>     {
>         static if (cases.length == 0)
>             static assert(false, "No match for args of type "~ Input.stringof);
>         else static if (__traits(compiles, cases[0](input))) // Can we
> call cases[0] on input?
>             return cases[0](input); // If yes, do it
>         else // else, recurse farther down
>             return .match1!(cases[1..$])(input);
>     }
> }
>
> string more(T...)(T t){ return "More than two args. Isn't life wonderful?";}
>
>
>
> void main()
> {
>     alias match!(
>         ()  => "No args",
>         (a) => "One arg, of type " ~ typeof(a).stringof ~ " with
> value: " ~ to!string(a),
>         (a, string b)=> "Two args (" ~ to!string(a) ~ ", " ~
> to!string(b) ~ "). I know the second one is a string.",
>         (a, b) => "Two args",
>         more
>     ) matcher;
>
>     writeln(matcher());
>     writeln(matcher(3.1416));
>     writeln(matcher(1, "abc"));
>     writeln(matcher(1, 1));
>     writeln(matcher(1, "abc", 3.1416));
>     writeln(matcher(1,1,1,1,1));
> }
October 24, 2012
Re: Mixin replacement for switch...case?
On Wed, Oct 24, 2012 at 9:56 AM, Jerome <jerome.spamable@yahoo.com> wrote:
>> Remark 1: I understand that your mixin will be expanded into cascaded
>> if...else statements. It would probably be more efficient to expand into
>> switch...case, don't you think?
>
>
> Oh! I've just figured out that it is not a mixin, but a function template.

That was to allow runtime arguments to be used. In your example, value
is a compile-time argument. In this case, all tests can be done at CT
and your code should result *only* in the right branch: no need to
develop an entire switch statement.
Next ›   Last »
1 2
Top | Discussion index | About this forum | D home