External Issue: Assymetry in iterating over 0:uint..10 by 1 or -1

Notifications Issues
1

20048, "cassella", "Assymetry in iterating over 0:uint..10 by 1 or -1", "2022-06-21T00:32:19Z"

Summary of Problem

As requested in #19991 comment

Iterating over this range by 1 works fine,

for i in 0:uint..10 by 1 do writeln(i);

but iterating over it by -1 reports an overflow problem:

$CHPL_HOME/modules/internal/ChapelRange.chpl:1918: error: halt reached - Iteration over a bounded range may be incorrect due to overflow.

This asymmetry is unsatisfying.

(Though it does run correctly with --fast.)

Possibly if the underlying C for loop used != instead of < to break out of the loop, this could be handled. Though @ronawho said there are good reasons for not doing this.

Associated Future Test(s):

None yet

Configuration Information

chpl version 1.27.0 pre-release (d8c48efbee)

CHPL_TARGET_PLATFORM: linux64
CHPL_TARGET_COMPILER: gnu
CHPL_TARGET_ARCH: x86_64
CHPL_TARGET_CPU: native *
CHPL_LOCALE_MODEL: flat
CHPL_COMM: gasnet *
  CHPL_COMM_SUBSTRATE: udp
  CHPL_GASNET_SEGMENT: everything
CHPL_TASKS: qthreads
CHPL_LAUNCHER: amudprun
CHPL_TIMERS: generic
CHPL_UNWIND: none
CHPL_MEM: jemalloc
CHPL_ATOMICS: cstdlib
  CHPL_NETWORK_ATOMICS: none
CHPL_GMP: none
CHPL_HWLOC: bundled
CHPL_RE2: bundled
CHPL_LLVM: unset
CHPL_AUX_FILESYS: none

gcc (Ubuntu 11.2.0-7ubuntu2) 11.2.0