On Monday, 13 January 2020 at 17:58:57 UTC, Steven Schveighoffer
wrote:
On 1/13/20 12:47 PM, H. S. Teoh wrote:
Why not write your own convenience wrapper?
auto firstElement(R)(R r)
if (isInputRange!R)
{
if (r.empty) throw new Exception(...);
return r.front;
}
auto e = myData.find!(e => blah(e)).firstElement;
I certainly can (and did). I was wondering if there was
something in Phobos to do it.
-Steve
`adjoin` can be used to run an inline lambda:
auto answer = arr.find!((item,x) => item.id ==
x)(id).adjoin!((n){enforce(!n.empty); return n.front;});
Using a simple alias you can have a flexible and nice to read
solution:
alias ensure(alias pred) = (n, const(char)[] msg = "`ensure`
failed"){enforce(pred(n), msg); return n;}; // module scope for
UFCS!
auto answer = arr.find!((item,x) => item.id == x)(id).ensure!(n
=> !n.empty).front;
or with custom message:
auto answer = arr.find!((item,x) => item.id == x)(id).ensure!(n
=> !n.empty)("element with id not found").front;
