Difference between revisions of "DIP40"
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* make D more consistent: it deduces template parameters for functions, so why not for constructors, when this is unambiguous? | * make D more consistent: it deduces template parameters for functions, so why not for constructors, when this is unambiguous? | ||
* it won't break any code. | * it won't break any code. | ||
+ | |||
+ | Note, just as for deduction of normal functions, it should work with 0 or more template parameters specified (ie the first k>=0 templates may be provided). | ||
== Example == | == Example == |
Revision as of 02:05, 13 May 2013
Contents
DIP 40: Template parameter deduction for constructors (do not read yet, still editing)
Title: | Template parameter deduction for constructors. |
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DIP: | 40 |
Version: | 1 |
Status: | Draft |
Created: | 2013-05-12 |
Last Modified: | 2013-05-12 |
Author: | Timothee Cour |
Links: |
Abstract
A proposed feature of C++14 is to introduce template parameter deduction for constructors, see paper, mentioned here. The idea is to deduce template parameters when calling a constructor given the arguments given to the constructor, whenever possible. A compile error occurs when the deduction is ambiguous. The benefits would be:
- make the code more DRY
- make boilerplate of class instantiators unnecessary in most cases (they're all over phobos, eg: std.typecons.tuple, std.typecons.rebindable etc)
- make D more consistent: it deduces template parameters for functions, so why not for constructors, when this is unambiguous?
- it won't break any code.
Note, just as for deduction of normal functions, it should work with 0 or more template parameters specified (ie the first k>=0 templates may be provided).
Example
import std.typecons;
auto a=Tuple!(int, double)(1,1.0); //not DRY
auto a=tuple(1,1.0); //boilerplate in std.typecons: requires auxiliary class instantiator function 'tuple' just to allow this
auto a=Tuple(1,1.0); //proposed syntax that deduces type parameters
Another example:
Extension
A possible extension is to also allow template parameter deduction for static functions, using the same mechanism as for templates.
Copyright
This document has been placed in the Public Domain.