DOKK / manpages / debian 11 / tcl8.6-doc / tcl_prefix.3tcl.en
prefix(3tcl) Tcl Built-In Commands prefix(3tcl) 







tcl::prefix - facilities for prefix matching








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










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.)







  

  
Accept only exact matches.

  

  
Use string in the error message at a mismatch. Default is
      “option”.

  

  
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 ..."














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 { }
}










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








prefix, table lookup







  

    8.6
    Tcl