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lsearch(3tcl) Tcl Built-In Commands lsearch(3tcl) 





NAME


lsearch - See if a list contains a particular element






SYNOPSIS


lsearch ?options? list pattern








DESCRIPTION


This command searches the elements of list to see if one of
    them matches pattern. If so, the command returns the index of the
    first matching element (unless the options -all or -inline are
    specified.) If not, the command returns -1 or (if options -all
    or -inline are specified) the empty string. The option
    arguments indicates how the elements of the list are to be matched against
    pattern and must have one of the values below:




MATCHING STYLE OPTIONS


If all matching style options are omitted, the default matching
    style is -glob. If more than one matching style is specified, the
    last matching style given takes precedence.



  

  
Pattern is a literal string that is compared for exact equality
      against each list element.

  

  
Pattern is a glob-style pattern which is matched against each list
      element using the same rules as the string match command.

  

  
Pattern is treated as a regular expression and matched against each
      list element using the rules described in the re_syntax reference
      page.

  

  
The list elements are in sorted order. If this option is specified,
      lsearch will use a more efficient searching algorithm to search
      list. If no other options are specified, list is assumed to
      be sorted in increasing order, and to contain ASCII strings. This option
      is mutually exclusive with -glob and -regexp, and is treated
      exactly like -exact when either -all or -not are
      specified.








GENERAL MODIFIER OPTIONS


These options may be given with all matching styles.



  

  
Changes the result to be the list of all matching indices (or all matching
      values if -inline is specified as well.) If indices are returned,
      the indices will be in ascending numeric order. If values are returned,
      the order of the values will be the order of those values within the input
      list.

  

  
The matching value is returned instead of its index (or an empty string if
      no value matches.) If -all is also specified, then the result of
      the command is the list of all values that matched.

  

  
This negates the sense of the match, returning the index of the first
      non-matching value in the list.

  

  
The list is searched starting at position index. The interpretation
      of the index value is the same as for the command string
      index, supporting simple index arithmetic and indices relative to the
      end of the list.








CONTENTS DESCRIPTION OPTIONS


These options describe how to interpret the items in the list
    being searched. They are only meaningful when used with the -exact
    and -sorted options. If more than one is specified, the last one
    takes precedence. The default is -ascii.



  

  
The list elements are to be examined as Unicode strings (the name is for
      backward-compatibility reasons.)

  

  
The list elements are to be compared using dictionary-style comparisons
      (see lsort for a fuller description). Note that this only makes a
      meaningful difference from the -ascii option when the
      -sorted option is given, because values are only dictionary-equal
      when exactly equal.

  

  
The list elements are to be compared as integers.

  

  
Causes comparisons to be handled in a case-insensitive manner. Has no
      effect if combined with the -dictionary, -integer, or
      -real options.

  

  
The list elements are to be compared as floating-point values.








SORTED LIST OPTIONS


These options (only meaningful with the -sorted option)
    specify how the list is sorted. If more than one is given, the last one
    takes precedence. The default option is -increasing.



  

  
The list elements are sorted in decreasing order. This option is only
      meaningful when used with -sorted.

  

  
The list elements are sorted in increasing order. This option is only
      meaningful when used with -sorted.

  

  
Inexact search when the list elements are in sorted order. For an
      increasing list the last index where the element is less than or equal to
      the pattern is returned. For a decreasing list the last index where the
      element is greater than or equal to the pattern is returned. If the
      pattern is before the first element or the list is empty, -1 is returned.
      This option implies -sorted and cannot be used with either
      -all or -not.








NESTED LIST OPTIONS


These options are used to search lists of lists. They may be used
    with any other options.



  

  
If this option is specified, the list is treated as consisting of groups
      of strideLength elements and the groups are searched by either
      their first element or, if the -index option is used, by the
      element within each group given by the first index passed to -index
      (which is then ignored by -index). The resulting index always
      points to the first element in a group.




The list length must be an integer multiple of
    strideLength, which in turn must be at least 1. A strideLength
    of 1 is the default and indicates no grouping.



  

  
This option is designed for use when searching within nested lists. The
      indexList argument gives a path of indices (much as might be used
      with the lindex or lset commands) within each element to
      allow the location of the term being matched against.

  

  
If this option is given, the index result from this command (or every
      index result when -all is also specified) will be a complete path
      (suitable for use with lindex or lset) within the overall
      list to the term found. This option has no effect unless the -index
      is also specified, and is just a convenience short-cut.










EXAMPLES


Basic searching:






lsearch {a b c d e} c


      → 2
lsearch -all {a b c a b c} c


      → 2 5




Using lsearch to filter lists:






lsearch -inline {a20 b35 c47} b*


      → b35
lsearch -inline -not {a20 b35 c47} b*


      → a20
lsearch -all -inline -not {a20 b35 c47} b*


      → a20 c47
lsearch -all -not {a20 b35 c47} b*


      → 0 2




This can even do a “set-like” removal operation:






lsearch -all -inline -not -exact {a b c a d e a f g a} a


      → b c d e f g




Searching may start part-way through the list:






lsearch -start 3 {a b c a b c} c


      → 5




It is also possible to search inside elements:






lsearch -index 1 -all -inline {{a abc} {b bcd} {c cde}} *bc*


      → {a abc} {b bcd}




The same thing for a flattened list:






lsearch -stride 2 -index 1 -all -inline {a abc b bcd c cde} *bc*


      → {a abc b bcd}








SEE ALSO


foreach(3tcl), list(3tcl), lappend(3tcl), lassign(3tcl),
    ledit(3tcl), lindex(3tcl), linsert(3tcl), llength(3tcl), lmap(3tcl),
    lpop(3tcl), lrange(3tcl), lremove(3tcl), lrepeat(3tcl), lreplace(3tcl),
    lreverse(3tcl), lseq(3tcl), lset(3tcl), lsort(3tcl), string(3tcl)






KEYWORDS


binary search, linear search, list, match, pattern, regular
    expression, search, string







  

    8.6
    Tcl