typeset -T versus typeset -r, bug or feature?

typeset -T versus typeset -r, bug or feature?

[Bart Schaefer]

Do this in an interactive shell so that the third line doesn't cause the
shell to exit:

typeset -T READ write
typeset -r READ
READ=wrong
write=right
print $READ

Re: typeset -T versus typeset -r, bug or feature?

[Peter Stephenson]

Bart Schaefer <schaefer@brasslantern.com> wrote:
> Do this in an interactive shell so that the third line doesn't cause the
> shell to exit:
> 
> typeset -T READ write
> typeset -r READ
> READ=wrong
zsh: read-only variable: READ
> write=right
> print $READ
right

This is a feature.  The parameters are different interfaces to the same
information.  "typeset -r write" will work as expected.  This is inevitable
given the current model for internal parameter storage.  I'm not
particularly attached to the current system anyway; parameters are probably
the clunkiest remaining parts of the system, full of ad-hoc tests,
over-complicated but under-powerful interfaces, and accesses into the
system at all sorts of different levels that ought to be implementation
details.

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR PLC, Churchill House, Cambridge Business Park, Cowley Road
Cambridge, CB4 0WZ, UK                          Tel: +44 (0)1223 692070


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Re: typeset -T versus typeset -r, bug or feature?

[Bart Schaefer]

On Sep 11,  2:45pm, Peter Stephenson wrote:
} Subject: Re: typeset -T versus typeset -r, bug or feature?
}
} Bart Schaefer <schaefer@brasslantern.com> wrote:
} > Do this in an interactive shell so that the third line doesn't cause the
} > shell to exit:
} > 
} > typeset -T READ write
} > typeset -r READ
} > READ=wrong
} zsh: read-only variable: READ
} > write=right
} > print $READ
} right
} 
} This is a feature.

OK, but note also that write=right did not convert write into a scalar
(see parallel thread about math assignment).  I'm not really griping
about this as it would mean an implicit un-tying, just noting a point
of interest.