[Issue 9550] Repeat!fun(size_t n)

[via Digitalmars-d-bugs]

https://issues.dlang.org/show_bug.cgi?id=9550

Vladimir Panteleev <dlang-bugzilla at thecybershadow.net> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |dlang-bugzilla at thecybershad
                   |                            |ow.net
         Resolution|---                         |WONTFIX

--- Comment #4 from Vladimir Panteleev <dlang-bugzilla at thecybershadow.net> ---
(In reply to daniel from comment #0)
> The use case is where you want to repeat an (impure) function n times lazily.

This doesn't make sense to me. Laziness and impurity do not mix.

> iota(100).map!(x => uniform(0, 76));

This code is conceptually wrong. By itself, this code does nothing. Advancing
the range will do nothing. Advancing the range while evaluating .front will do
something; but so will accessing .front in a loop without advancing the range.
The resulting range object is broken by design in several aspects.

It seems to me that you are trying to shoehorn an operation into a design which
was not really meant for it. In the case of random numbers, the proper solution
would be a PRNG range, which has correctly-implemented .front (which always
returns the same value while not advancing), .popFront (which advances the
PRNG), and .save (which makes a copy of the PRNG's state).

I'll close this as the last activity on this bug was over 4 years ago. If you
think you have a valid use case, feel free to reopen, though I would suggest
creating a forum thread about this first instead.

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