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On 8/10/2014 12:13 PM, Tim Hill wrote:
Lua doesn't use sigils
nor is its parser capable of dealing with keywords
as identifiers. So, in
order to prevent code breakage, some of us Lua users
are conservative when it
comes to adding new keywords.
I seem to recall that very early versions of Lua made some
use of sigils, but I could be wrong on this.
—Tim
Lua didn't have full lexical scoping with true closures until
version 5.0--in prior versions references to upvalues were denoted
by a prefixed % sigil ( or was it considered a unary operator?). The
term "upvalue" itself is historical and probably would not been the
term chosen if the concept had been introduced concurrently with
lexical scoping, etc. It took me a while to decipher *tm in the 5.1
and subsequent C source code as being an abbreviation for the
obsolete term "tag method". IIRC, the even older term "fallback"
appears as comments in a place or two even in 5.3 source.
None of this account is intended to be critical of anyone, the Lua
team least of all: Lua source is a work of art. But knowing some Lua
history helps us understand what Lua is now. +1 to Tim for
remembering this item. I would heartily recommend spending the time
to study the documentation of earlier versions. For those who have
both the time and the C skill, the source code of earlier versions
is a worthwhile study as well.
-- Mike
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