ulis: If, for some syntax analyzis, you need to know the level of nested braces inside a list, here is a tiny proc that do that.
It returns 0 for "this is a list", 1 for "{this is a list}" or "this {is a} list", and so on.
proc listlevel {text} {
set len [llength [split $text]]
for {set count 0} {$len!=[set len [llength $text]]} {incr count} {
# Used to be [eval concat $text] but this is safer
set text [eval [linsert $text 0 concat]]
}
return $count
}ulis: This proc doesn't get the good result because llength $text can't differentiate between {{this is a list}} and {{{this is a list}}} (each returns 1). Applied to the test below it returns: 0 0 0 2 2 3 1. (Expected results are: 0 0 0 1 1 2 2).
ulis: Here is a proc that gets the expected results from the test below. (Maybe somebody will find a flaw?)
proc listlevel {list} \
{
# initial length & count
set len [string length $list]
set count 0
# while string length differs between list & concatened list
while {[string length [set list [eval concat $list]]] != $len} \
{
# update length & count
set len [string length $list]
incr count
}
return $count
}Can somebody explain me why eval [linsert $list 0 concat] is better than [eval concat $list in this context?
AK -- eval is given a pure list and goes through a specially optimized path for the eval/linsert combo. Without the linsert 'concat' is no pure list and thus eval does the regular stuff, which is slower.
Results:
set text "this is a list"
puts "$text: [listlevel $text]"
-> this is a list: 0
set text {this is a list}
puts "$text: [listlevel $text]"
-> this is a list: 0
set text [list this is a list]
puts "$text: [listlevel $text]"
-> this is a list: 0
set text [list "this is a list"]
puts "$text: [listlevel $text]"
-> {this is a list}: 1
set text {{this is a} list}
puts "$text: [listlevel $text]"
-> {this is a} list: 1
set text {{this {is a}} list}
puts "$text: [listlevel $text]"
-> {this {is a}} list: 2
set text {{{this is a list}}}
puts "$text: [listlevel $text]"
-> {{this is a list}}: 2ulis: Tcl makes no difference between "this is a list" and [list this is a list] so I gave them the 0 level.
You can need to differentiate empty strings, one word strings and multi words strings before nested lists.
Slight problem. It doesn't like list encapsulated single element lists. Nil and multi-element lists work:
% listlevel [list a]
0
% listlevel [list {a}]
0
% listlevel [list {}]
1
% listlevel [list {a b}]
1
%