NAME

       tcl::prefix - facilities for prefix matching

SYNOPSIS

       ::tcl::prefix all table string
       ::tcl::prefix longest table string
       ::tcl::prefix match ?option ...? table string
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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 prefix 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 ALSO

       lsearch(3tcl), namespace(3tcl), string(3tcl), Tcl_GetIndexFromObj(3tcl)

KEYWORDS

       prefix, table lookup