string is class ?-strict? ?-failindex varname? string
Returns 1 if string is a valid member of the specified character class, otherwise returns 0. If -strict is specified, then an empty string returns 0, otherwise an empty string will return 1 on any class. If -failindex is specified, then if the function returns 0, the index in the string where the class was no longer valid will be stored in the variable named varname. The varname will not be set if the function returns 1. The following character classes are recognized (the class name can be abbreviated):
In the case of boolean, true and false, if the function will return 0, then the varname will always be set to 0, due to the varied nature of a valid boolean value.
string is digit string will return 1 if string is composed of "Any Unicode digit character." Then it goes on to say that "this includes characters outside of the [0-9] range." What other characters, aside from [0-9], are members of the digit character class?
RS As Tcl is great for introspection, a few lines of code give the answer:
proc udigits max {
set res {}
for {set i 0} {$i<=$max} {incr i} {
if [string is digit [format %c $i]] {
append res "\\u[format %04x $i] "
}
}
set res
}
% udigits 65535\u0030 \u0031 \u0032 \u0033 \u0034 \u0035 \u0036 \u0037 \u0038 \u0039 \u0660 \u0661 \u0662 \u0663 \u0664 \u0665 \u0666 \u0667 \u0668 \u0669 \u06f0 \u06f1 \u06f2 \u06f3 \u06f4 \u06f5 \u06f6 \u06f7 \u06f8 \u06f9 \u0966 \u0967 \u0968 \u0969 \u096a \u096b \u096c \u096d \u096e \u096f \u09e6 \u09e7 \u09e8 \u09e9 \u09ea \u09eb \u09ec \u09ed \u09ee \u09ef \u0a66 \u0a67 \u0a68 \u0a69 \u0a6a \u0a6b \u0a6c \u0a6d \u0a6e \u0a6f \u0ae6 \u0ae7 \u0ae8 \u0ae9 \u0aea \u0aeb \u0aec \u0aed \u0aee \u0aef \u0b66 \u0b67 \u0b68 \u0b69 \u0b6a \u0b6b \u0b6c \u0b6d \u0b6e \u0b6f \u0be7 \u0be8 \u0be9 \u0bea \u0beb \u0bec \u0bed \u0bee \u0bef \u0c66 \u0c67 \u0c68 \u0c69 \u0c6a \u0c6b \u0c6c \u0c6d \u0c6e \u0c6f \u0ce6 \u0ce7 \u0ce8 \u0ce9 \u0cea \u0ceb \u0cec \u0ced \u0cee \u0cef \u0d66 \u0d67 \u0d68 \u0d69 \u0d6a \u0d6b \u0d6c \u0d6d \u0d6e \u0d6f \u0e50 \u0e51 \u0e52 \u0e53 \u0e54 \u0e55 \u0e56 \u0e57 \u0e58 \u0e59 \u0ed0 \u0ed1 \u0ed2 \u0ed3 \u0ed4 \u0ed5 \u0ed6 \u0ed7 \u0ed8 \u0ed9 \u0f20 \u0f21 \u0f22 \u0f23 \u0f24 \u0f25 \u0f26 \u0f27 \u0f28 \u0f29 \u1040 \u1041 \u1042 \u1043 \u1044 \u1045 \u1046 \u1047 \u1048 \u1049 \u1369 \u136a \u136b \u136c \u136d \u136e \u136f \u1370 \u1371 \u17e0 \u17e1 \u17e2 \u17e3 \u17e4 \u17e5 \u17e6 \u17e7 \u17e8 \u17e9 \u1810 \u1811 \u1812 \u1813 \u1814 \u1815 \u1816 \u1817 \u1818 \u1819 \uff10 \uff11 \uff12 \uff13 \uff14 \uff15 \uff16 \uff17 \uff18 \uff19
For instance, \u0660-\u0669 are "Indo-Arabic" digits as used in Arab countries. \uFF10-\uFF19 are "fullwidth" variants of 0-9, etc.
Lars H: Quite a lot, as you can see; there are plenty of digit sets in Unicode. The authorative source on the subject should be the Unicode Character Database (see [L1 ] for format and links), but whether Tcl really uses that is another matter. A comparison of the above with the UCD shows that [string is digit] returns 1 for most (but not quite all!) of the characters from the class Nd (decimal digits), so that is probably what it is supposed to test.
escargo 14 Mar 2006 - I had my own peek starting at http://www.unicode.org/charts/symbols.html where there are links to four PDF files under Numbers and Digits: ASCII Digits, Fullwidth ASCII Digits, Number Forms, and Super and Subscripts. All of these might legitimately contain digits.
NEM 14 Mar 2006: Interesting. Note though that most of these "digits" are not valid for expressions fed to expr. So, if you are using [string is digit] to validate arguments to expressions then you probably have a bug.
See also:
Tcl syntax help - Category Command - Category String Processing