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

Tcl                                                    8.6                                          prefix(3tcl)