[Gretl-devel] Re: foreach-loop over arrays

On Fri, 8 Jan 2021, Artur Tarassow wrote: > Am 08.01.21 um 15:12 schrieb Allin Cottrell: >> >> "loop foreach" is intended for iterating across strings, and allowing >> iteration over bundle keys and arrays of strings is a special case of >> that. But in general "foreach" for arrays is redundant since they are >> indexed and ordered. > > Thanks for the clarification, Allin. I agree that with your redundancy > argument to some degree. > > However, I've (still) have two remarks on the current behavior: > > 1) Using a foreach loop looks very natural (at least) to me when > iterating over bundles and matrices -- even though it may be redundant > [...] OK, I take your point. Now in git   loop foreach i <array> is taken as syntactic sugar for   loop i=1..nelem(<array>) (If <array> is not an array of strings, $i just gives the string representation of the index.) > 2) If the foreach type of loop is not supported for matrices and > bundles, I think it should not work at all when iterating over these > data types and actually throw an error. This goes back to the original point of a foreach loop, namely iterating over strings (with string substitution supported via $i). From that point of view, when you said loop foreach i B ... endloop it would mean: iterate over an array of literal strings containing the single element "B". The fact that "B" might be the name of an array was irrelevant, and ignored. But since that interpretation has already been breached for bundles and arrays of strings, it might as well be breached for all array types. (Note: you still get the traditional interpretation if "foreach i" is followed by more than one string.)