On Mon, Sep 8, 2008 at 1:29 PM, Jon Lang <[EMAIL PROTECTED]> wrote: > TSa wrote: >> Ahh, I see. Thanks for the hint. It's actually comma that builds lists. >> So we could go with () for undef and require (1,) and (,) for the single >> element and empty list respectively. But then +(1,2,3,()) == 4. > > Actually, note that both infix:<,> and circumfix:<[ ]> can be used to > build lists; so [1] and [] can be used to construct single-element and > empty lists, respectively.
It may be worth noting here that in Python, (1) is a scalar integer value and (1,) is a tuple of length 1, but the empty tuple is represented by commaless (). Thus len(()) is 0, len((,)) is a syntax error, len((1,)) is 1, and len((1)) is a type error. Also, all three of the empty tuple (), the empty list [], and the nil value None are distinct from each other. -- Mark J. Reed <[EMAIL PROTECTED]>
