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
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.
-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
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.
-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 ascending 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
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.
-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
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.
-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
precedence. 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
element 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
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 {{abc abc} {abc bcd} {abc cde}} *bc*
-> {abc abc} {abc 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 8.6.16 - Generated Mon Jan 6 10:37:53 CST 2025