On Saturday, 19 May 2012 at 23:03:50 UTC, Walter Bright wrote:
http://www.reddit.com/r/programming/comments/tui75/lazy_evaluation_of_function_arguments_in_d/
Lazy evaluation has been discussed previously, but this topic is
important and the problems have not been solved yet.
Functional languages, like Haskel, Scala or F#, have the
semantics of lazy evaluation which is to evaluate things at most
once. Evaluating many times is accomplished via a function or
delegate.
Thus lazy in D is (IMO):
* confusing, because it doesn't take into account lazy semantics
* close to useless, because functions or delegates could do the
same job and not confuse the users
* somehow hiding the need to have the functionality of evaluating
an expression at most once. For example, I need this to work with
immutable data, but it is not possible conceptually at this
moment (clearly, evaluating and storing the result would mutate
the data). I understand that designing this would mean there is
the need for synchronization for immutable data. But at least
this functionality could exist for pure functions.
