How to create a custom max() function without the ambiguity error.
aldacron at gmail.com
Fri Dec 6 22:14:10 UTC 2019
On Friday, 6 December 2019 at 21:02:53 UTC, realhet wrote:
> Here's my latest attempt on EXTENDING std.algorithm.max's
> functionality with a max operation on a custom type.
> The type is the GLSL vec2 type which does the max operation
> The D std implementation uses the < operator, but with
> overriding that for my custom type it is impossible to realise.
> -> max(vec2(1, 2), vec2(2,1)) == vec2(2,2)
The reason you're having so much trouble with this is that you're
violating the contract of max. It's a template, so it's already
set up to work with custom types without any need to write a
custom max function, as long as the types adhere to the contract.
Consider other functions in std.algorithm, such as sort or equal,
that allow you to pass a custom predicate. max doesn't have that
because, by defintion, there is only one comparison for it to do:
>. Any type that doesn't support that isn't going to work with
Moreover, your return value violates the function's contract:
"Iterates the passed arguments and return the maximum value."
You aren't returning the maximum value. You're returning a new
value constructed from the maximum components of the two
parameters. That is not the same behavior as max(1, 3).
Given that your function has a different contract, it should also
have a different name.
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