On Sat, 31 Aug 2013 12:46:52 +0100, Steven D'Aprano
<steve+comp.lang.pyt...@pearwood.info> wrote:
# THIS DOES NOT HAPPEN IN PYTHON
# or any other language, as far as I am aware
x = 23
y = x # y now has the value 23
x = 42 # change the value of the object ### NOT SO! ###
print y
=> prints 42
Not directly, but FORTRAN did (does?) allow you to achieve this
oh-so-undesirable result indirectly.
FORTRAN passes arguments to functions and procedures by reference. That
includes passing constants, which effectively get put into hidden
variables and passed across. Changes to the "constant" parameters in the
function can happen just as with any pass-by-reference, which would be
fine if you promptly threw the constant away. Unfortunately smart
compilers used to (still do?) keep pools of these common constant
"variables" around rather than creating new ones all the time, so changes
to "constants" persisted. Many's the poor natural scientist who was
perplexed to find that 0 suddenly had the value 1!
--
Rhodri James *-* Wildebeest Herder to the Masses
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