prefix(n) Tcl Built-In Commands prefix(n)______________________________________________________________________________NAME
tcl::prefix - facilities for prefix matching
SYNOPSIS
::tcl::prefix all table string
::tcl::prefix longest table string
::tcl::prefix match ?option ...? table string
_________________________________________________________________DESCRIPTION
This document describes commands looking up a prefix in a list of
strings. The following commands are supported:
::tcl::prefix all table string
Returns a list of all elements in table that begin with the pre‐
fix string.
::tcl::prefix longest table string
Returns the longest common prefix of all elements in table that
begin with the prefix string.
::tcl::prefix match ?options? table string
If string equals one element in table or is a prefix to exactly
one element, the matched element is returned. If not, the result
depends on the -error option. (It is recommended that the table
be sorted before use with this subcommand, so that the list of
matches presented in the error message also becomes sorted,
though this is not strictly necessary for the operation of this
subcommand itself.)
-exact
Accept only exact matches.
-message string
Use string in the error message at a mismatch. Default is
“option”.
-error options
The options are used when no match is found. If options
is empty, no error is generated and an empty string is
returned. Otherwise the options are used as return
options when generating the error message. The default
corresponds to setting “-level 0”. Example: If “-error
{-errorcode MyError -level 1}” is used, an error would be
generated as:
return -errorcode MyError -level 1 -code error \
"ambiguous option ..."
EXAMPLES
Basic use:
namespace import ::tcl::prefix
prefix match {apa bepa cepa} apa
→ apa
prefix match {apa bepa cepa} a
→ apa
prefix match -exact {apa bepa cepa} a
→ bad option "a": must be apa, bepa, or cepa
prefix match -message "switch" {apa ada bepa cepa} a
→ ambiguous switch "a": must be apa, ada, bepa, or cepa
prefix longest {fblocked fconfigure fcopy file fileevent flush} fc
→ fco
prefix all {fblocked fconfigure fcopy file fileevent flush} fc
→ fconfigure fcopy
Simplifying option matching:
array set opts {-apa 1 -bepa "" -cepa 0}
foreach {arg val} $args {
set opts([prefix match {-apa -bepa -cepa} $arg]) $val
}
Creating a switch that supports prefixes:
switch [prefix match {apa bepa cepa} $arg] {
apa { }
bepa { }
cepa { }
}
SEE ALSOlsearch(n), namespace(n), string(n), Tcl_GetIndexFromObj(3)KEYWORDS
prefix, table lookup
Tcl 8.6 prefix(n)
