lsearch - See if a list contains a particular element
lsearch ?options? list pattern
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. The option
arguments indicates how the elements of the list are to be matched against
pattern and must have one of the values below:
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.
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 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.
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.
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.
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.
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}
foreach(3tcl), list(3tcl), lappend(3tcl), lindex(3tcl),
linsert(3tcl), llength(3tcl), lset(3tcl), lsort(3tcl), lrange(3tcl),
lreplace(3tcl), string(3tcl)
binary search, linear search, list, match, pattern, regular
expression, search, string