The artist formerly known as {expand}. See TIP 293 [L1 ] for details.
RLH This is much better IMHO.
jcw - HURRAY!
RS Note that in re_syntax, * stands for "zero or more", which is exactly the unique cardinality of an {expand}ed item...
DKF: Similarly in string match syntax.
SYStems I vote yes. I don't think though that its necessary to deprecate {expand}, but I agree on deprecating {} it does look like syntax error rather than a feature.
RLH I think {expand} should be removed completely. It is not in the language "official" yet and so it should be yanked to make sure no abuse occurs.
JMN Well.. {*} looks to me like a nipple.. which is clearly better than a wart.
CN slightly regrets that {expand} is now gone - I was looking forward for possible future enhancements along the same line, like for example
lappend mylist {sort|toupper|regmatch [0-9]+}$somelistto specify a chain of filters for the expansion. But I suppose that people for whom {expand} is a wart will classify this a as a tumor... ;-)
DKF: It's also trivially replacable using {*}[...] and some commands to preprocess the list.
SYStems or you can just
lappend mylist {*}[lsort [string toupper [regmatch {[0-9]+} $somelist]]]moral is {*} is not a shorthand for other commands, its a new feature, although for this particular example you could have just used
set mylist [concat $mylist [lsort [string toupper [regmatch {[0-9]+} $somelist]]] ]AMG: When I have a long command but don't feel like using \ at the end of every line, I sometimes do the following:
set data [dict create {*}{
key1 val1 key2 val2
key3 val3 key4 val4
key5 val5 key6 val6
}]Of course, in this case I could have just left out the [dict create] and instead relied on the internal representation being generated the first time I tried accessing $data as a dict. But the above is slightly faster and clearer... well, except for the {*} nonsense, of course. :^) Given a bit of time, I'm sure I could come up with a more realistic example, but I actually find myself doing the above in real code (if anything I write can be said to be "real").
This usage of {*} provides quoting without grouping. Dollar signs and square brackets become ordinary characters, sequences of unquoted whitespace and newlines are delimiters, and the resulting list elements (all of which are pure strings) are placed one-after-the-other into the command's objv list without any extra interpretation. Backslashes, paired braces, and paired double quotes still function as quoting/grouping characters. ("Grouping" means to disable the special meaning of characters that would otherwise be treated as delimiters.)
For the impatient, see Expansion with {*} in Tcl 8.4
[ Category Syntax | Dodekalogue ]