[Octave-bug-tracker] [bug #53331] Can't make function output argument persistent (poor man's constant)

[Oliver Heimlich]

URL:
  <http://savannah.gnu.org/bugs/?53331>

                 Summary: Can't make function output argument persistent (poor
man's constant)
                 Project: GNU Octave
            Submitted by: oheim
            Submitted on: Mon 12 Mar 2018 09:52:25 PM CET
                Category: Interpreter
                Severity: 3 - Normal
                Priority: 5 - Normal
              Item Group: Regression
                  Status: None
             Assigned to: None
         Originator Name: Oliver Heimlich
        Originator Email: 
             Open/Closed: Open
         Discussion Lock: Any
                 Release: dev
        Operating System: Any

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Details:

The following is a common(?) idiom in Octave to define a constant value: To
define a function without parameters.

To prevent multiple initialization of a computed value, it can be made
persistent.  However, that fails in the current dev version.


>> function x = foo (); persistent x = 1; endfunction
>> foo
error: can't make function parameter x persistent
error: called from
    foo at line 1 column 22


I can understand that input(!) arguments cannot be made persistent.  But,
shouldn't that be possible for output arguments?




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