[Octave-bug-tracker] [bug #59229] Regression in handling inf as for-loop limits

[anonymous]

URL:
  <https://savannah.gnu.org/bugs/?59229>

                 Summary: Regression in handling inf as for-loop limits
                 Project: GNU Octave
            Submitted by: None
            Submitted on: Tue 06 Oct 2020 01:33:19 PM UTC
                Category: Interpreter
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Regression
                  Status: None
             Assigned to: None
         Originator Name: 
        Originator Email: 
             Open/Closed: Open
                 Release: dev
         Discussion Lock: Any
        Operating System: GNU/Linux

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Details:

This code used to work in Octave 5.2 but now causes an out of memory error in
Octave 7.0.0 (dev):


lo = +inf;
hi = -inf;
# lo and hi are refined here as required by the problem instance
# If the instance is empty, then lo and hi are unchanged.
for i = lo:hi
  # do something
endfor
# The idea is that for empty problem instances,
# the for-loop would become empty as well and trivially backtrack.


This used to work as intended but now results in this error in Octave 7.0.0:

error: out of memory or dimension too large for Octave's index type


The problem is specific to the use of inf or -inf in for-loop limits, because
the following loop does not cause an error:


lo = +1e30; # some value much bigger than memory would allow
hi = -1e30;
for i = lo:hi
  # do something
endfor
# Empty loop trivially exits.


The problem has been temporarily worked around by using a very large finite
value instead of inf.





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