On 2003-01-21 at 11:09:21, Thom Boyer wrote:
> One of the most... er, *interesting*, dodges I've seen in this area is the
> one used by Squeak (a Smalltalk variant). Squeak spells assignment with an
> underscore ("_"), but the Squeak system *draws* it as a left-pointing arrow.
There's a history behind that particular choice; before the ISO-8859
standardization, people got the characters they needed by making
"mostly-ASCII" character sets that differed in small ways from the
original US standard. Having a left-pointing arrow in place of the
underscore was a common variant (used in, for instance, PET ASCII
on Commodore computers, which also had other substitutions, such
as the letter pi in place of tilde, and the British pound symbol
in place of backslash).
Assignment has been written as a left arrow in pseudocode for
decades, but because the character was left out of ASCII (although
it's in EBCDIC), its use within actual languages has been pretty
much limited to those which already specify their own character set
and/or glyph display anyway (such as APL). I do know of at
least one Pascal derivative that uses '<-' as a synonym for ':=',
requiring whitespace if your intent is the relational operator followed
by unary minus.
Squeak does, incidentally, also let you use := for assignment, which is
the standard for ASCII Smalltalk.
--
Mark REED | CNN Internet Technology
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