string - Manipulate strings

http://purl.org/tcl/home/man/tcl8.4/TclCmd/string.htm

Ensembliform command for manipulating strings.

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'''[string bytelength]''' ''string''

'''[string compare]''' ''?'''''-nocase'''''? ?'''''-length int'''''? string1 string2''

'''[string equal]''' ''?'''''-nocase'''''? ?'''''-length int'''''? string1 string2''

'''[string first]''' ''string1 string2 ?startIndex?''

'''[string index]''' ''string charIndex''

'''[string is]''' ''class ?'''''-strict'''''? ?'''''-failindex''' ''varname? string''

'''[string last]''' ''string1 string2 ?startIndex?''

'''[string length]''' ''string''

'''[string map]''' ''?'''''-nocase'''''? charMap string''

'''[string match]''' ''?'''''-nocase'''''? pattern string''

'''[string range]''' ''string first last''

'''[string repeat]''' ''string count''

'''[string replace]''' ''string first last ?newstring?''

'''[string reverse]''' ''string''

'''[string tolower]''' ''string ?first? ?last?''

'''[string totitle]''' ''string ?first? ?last?''

'''[string toupper]''' ''string ?first? ?last?''

'''[string trim]''' ''string ?chars?''

'''[string trimleft]''' ''string ?chars?''

'''[string trimright]''' ''string ?chars?''

'''[string wordend]''' ''string charIndex''

'''[string wordstart]''' ''string charIndex''

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Is this correct behavior?
 % set str ""
 % string is true $str
 1
 % string is false $str
 1
 % string is integer $str
 1
 % string is alpha $str
 1

Sadly, yes, that is correct.  You'll have to use
the '''-strict'''
option to keep empty strings from passing all tests.

This is an unfortunate legacy from the origin of
the [[string is]] command as a tool for [entry]
validation, where it's important the empty string
pass everything so that every input doesn't fail
immediately.

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'''Using string functions for binary data'''

Is there a full documentation what of these functions are save to use with binary data?  What I have found out so far:

safe:
   * string range

unsafe:
   * string index  (at least ''string index $data end'' garbles $data)

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[MG] Since Tcl 8.5, an index in the [string] commands can include basic math;

 string range $string $startChar+1 $endChar-1

is now equivalent to

 string range $string [expr {$startChar + 1}] [expr {$endChar - 1}]

While the first may be clearer, though, it seems to be (potentially quite a lot) slower for me, running 8.5a6:

 % set string "This is a test string"
 This is a test string
 % set startChar 3
 3
 % set endChar 12
 12
 
 % time {string range $string [expr {$startChar+1}] [expr {$endChar-1}]} 500000
 2.55498 microseconds per iteration
 % time {string range $string $startChar+1 $endChar-1} 500000
 5.092856 microseconds per iteration

Using [expr] there is quite drastically faster...

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See also:

   * [string forward compatibility]
   * [Additional string functions]
   * [string compare ...]

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