PNut/Spin2 Latest Version (v50 - PLOT bitmaps, DITTO code, ORGH inline, @\"string\n", IF_??? DEBUG)

Francis Bauer

@wummi said:
Hi Chip,
I found a strange behavior with REPEAT <count> WITH <variable> when count is zero.

PUB go () | i
  repeat 0 with i
    debug(sdec(i))
{ debug output
Cog0  i = 0
Cog0  i = -1
}

I expected debug(sdec(i)) is never executed, but it executes twice.

I believe this behavior is expected. The Spin document indicates that the count value is normally expected to be a number greater than 0.
The WITH form of the REPEAT statement is a smaller/faster version than the REPEAT FROM statement.

v40 2023-09-21 ● New smaller/faster REPEAT form added for iterating a variable from 0 to n-1, where n > 0.
   REPEAT n WITH i 'best way to iterate a variable from 0 to n - 1
   REPEAT i from 0 to n - 1 'general equivalent, though WITH needs n > 0

Example:

_clkfreq = 200_000_000

PUB go () | i,n

  repeat 0 with i
    debug("with loop: ",sdec(i))

  n := 0  
  repeat i from 0 to n-1
    debug("from loop: ",sdec(i))

Output:
Cog0  with loop: i = 0                                                          
Cog0  with loop: i = -1                                                         
Cog0  from loop: i = 0                                                          
Cog0  from loop: i = -1

wummi

OK, i do not now that n must be greater than 0

evanh

Undefined is not the same as expected.