OpenEuphoria

Re: FOR i ...

• Posted by Pete Lomax <petelomax at blueyonder.??.uk> Nov 15, 2007
• 545 views

Derek Parnell wrote:
> 
> the point of difference is whether or not the coder wants
> the iterator variable to be declared in the FOR statement or prior
Agreed, mostly [see PS].

>     for <res-word> i = A to B by C do

Fine by me. Experimenting, I found that (on both 2.4 & 3.1):

for integer=1 to 10 do end for
  for atom=1 to 10 do end for

compiles cleanly (but obviously does nothing). However any attempt to reference
the [daftly named] control var, such as ?integer, triggers an error. Hence, I
believe, the above proves A) that integer/atom could be used as the <res-word>
with no changes to lexer/tokeniser, obviously changes are needed in the scanner
no matter what <res-word> is, and B) such would not introduce any backward
incompatibility, thus I propose:

integer i
   for integer i=1 to 10 do -- re-uses existing i
   end for
   ?i  -- valid, prints 11

It should also be stated that, both for performance reasons and since it is
illegal to modify a for loop control var, any attempts at user defined type
checking on a for loop var simply won't happen. I'd further impose a compile time
error on any attempt to use a udt.

Regards,
Pete
PS Of course this does not actually solve the original problem of multiple and
confusing i in trace/ex.err, <ahem> as my first suggestion did </ahem>, but at
least provides a work-around, and an oft-requested missing feature.