canFind typing

[bearophile]

I have used std.algorithm.canFind with different tuple types by 
mistake, and the compiler has not complained. So to show it I 
have written some reduced code that uses just numbers:



import std.algorithm: canFind;
void main() {
int[] arr1 = [1, 2];
double x1 = 2.0;
assert(arr1.canFind(x1));
double[] arr2 = [1.0, 2.0];
int x2 = 2;
assert(arr2.canFind(x2));
}


Are both of those canFind calls acceptable?

Bye,
bearophile

Re: canFind typing

[Jonathan M Davis]

On Thursday, November 29, 2012 15:28:56 bearophile wrote:
> I have used std.algorithm.canFind with different tuple types by
> mistake, and the compiler has not complained. So to show it I
> have written some reduced code that uses just numbers:
> 
> 
> import std.algorithm: canFind;
> void main() {
> int[] arr1 = [1, 2];
> double x1 = 2.0;
> assert(arr1.canFind(x1));
> double[] arr2 = [1.0, 2.0];
> int x2 = 2;
> assert(arr2.canFind(x2));
> }
> 
> 
> Are both of those canFind calls acceptable?

Why wouldn't they be? You can compare int and double, and that's what find and 
canFind care about.

- Jonathan M Davis

Re: canFind typing

[bearophile]

Jonathan M Davis:

Why wouldn't they be? You can compare int and double, and 
that's what find and canFind care about.


Right, it's a matter of equality operator.

In my code I was performing canFind on an array of tuples. So I 
didn't realize that the following code (where both tuple field 
type and field name are different) is accepted in D (probably I 
am getting used to the higher type strictness of functional 
languages):



import std.typecons: Tuple;
alias T1 = Tuple!(int, "x");
alias T2 = Tuple!(double, "y");
void main(string[] args) {
assert(T1(1) == T2(1));
}


Bye,
bearophile