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lsearch(n)                   Tcl Built-In Commands                  lsearch(n)



______________________________________________________________________________


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 spec-
       ified)  the  empty string.  The option arguments indicates how the ele-
       ments 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.

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

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

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

       -sorted
              The list elements are in sorted order.  If this option is speci-
              fied, 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  speci-
              fied.

   GENERAL MODIFIER OPTIONS
       These options may be given with all matching styles.

       -all   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 numeric order. If values
              are returned, the order of the values will be the order of those
              values within the input list.

       -inline
              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.

       -not   This negates the sense of the match, returning the index of  the
              first non-matching value in the list.

       -start index
              The  list is searched starting at position index.  The interpre-
              tation 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.

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

       -dictionary
              The list elements are to be compared using dictionary-style com-
              parisons  (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.

       -integer
              The list elements are to be compared as integers.

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

       -real  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 prece-
       dence.  The default option is -increasing.

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

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

       -bisect
              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.

       -index indexList
              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 ele-
              ment to allow the location of the term being matched against.

       -subindices
              If this option is given, the index result from this command  (or
              every  index  result when -all is also specified) will be a com-
              plete 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}


SEE ALSO

       foreach(n),  list(n),  lappend(n),  lindex(n),  linsert(n), llength(n),
       lset(n), lsort(n), lrange(n), lreplace(n), string(n)


KEYWORDS

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



Tcl                                   8.6                           lsearch(n)

tcl 8.6.11 - Generated Wed Jan 20 14:38:37 CST 2021
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