'\"
'\" Copyright (c) 2022 Eric Taylor.  All rights reserved.
'\"
'\" See the file "license.terms" for information on usage and redistribution
'\" of this file, and for a DISCLAIMER OF ALL WARRANTIES.
'\"
.TH lseq n 8.7 Tcl "Tcl Built-In Commands"
.so man.macros
.BS
'\" Note:  do not modify the .SH NAME line immediately below!
.SH NAME
lseq \- Build a numeric sequence returned as a list
.SH SYNOPSIS
\fBlseq \fIStart \fR?(\fB..\fR|\fBto\fR)? \fIEnd\fR ??\fBby\fR? \fIStep\fR?

\fBlseq \fIStart \fBcount\fR \fICount\fR ??\fBby\fR? \fIStep\fR?

\fBlseq \fICount\fR ?\fBby \fIStep\fR?
.BE
.SH DESCRIPTION
.PP
The \fBlseq\fR command creates a sequence of numeric values using the given
parameters \fIStart\fR, \fIEnd\fR, and \fIStep\fR. The \fIoperation\fR
argument ".." or "to" defines the range. The "count" option is used
to define a count of the number of elements in the list. A short form use of
the command, with a
single count value, will create a range from 0 to count-1.

The \fBlseq\fR command can produce both increasing and decreasing sequences. When
both Start and End are provided without a Step value, then if Start <= End,
the sequence will be increasing and if Start > End it will be decreasing. If a
Step vale is included, it's sign should agree with the direction of the
sequence (descending -> negative and ascending -> positive), otherwise an
empty list is returned.  For example:

.CS \"
    % lseq 1 to 5    ;# increasing
    1 2 3 4 5

    % lseq 5 to 1    ;# decreasing
    5 4 3 2 1

    % lseq 6 to 1 by 2   ;# decreasing, step wrong sign, empty list

    % lseq 1 to 5 by 0   ;# all step sizes of 0 produce an empty list

.\"
.CE

The numeric arguments, \fIStart\fR, \fIEnd\fR, \fIStep\fR, and \fICount\fR,
may also be a valid expression. The expression will be evaluate and the
numeric result be used.  An expression that does not evaluate to a number will
produce an invalid argument error.

.SH EXAMPLES
.CS
.\"

 lseq 3
 \(-> 0 1 2

 lseq 3 0
 \(-> 3 2 1 0

 lseq 10 .. 1 by -2
 \(-> 10 8 6 4 2

 set l [lseq 0 -5]
 \(-> 0 -1 -2 -3 -4 -5

 foreach i [lseq [llength $l]] {
   puts l($i)=[lindex $l $i]
 }
 \(-> l(0)=0
    l(1)=-1
    l(2)=-2
    l(3)=-3
    l(4)=-4
    l(5)=-5

 foreach i [lseq [llength $l]-1 0] {
    puts l($i)=[lindex $l $i]
 }
 \(-> l(5)=-5
    l(4)=-4
    l(3)=-3
    l(2)=-2
    l(1)=-1
    l(0)=0

 set sqrs [lmap i [lseq 1 10] {expr $i*$i}]
 \(-> 1 4 9 16 25 36 49 64 81 100
.\"
.CE
.SH "SEE ALSO"
foreach(n), list(n), lappend(n), lassign(n), lindex(n), linsert(n), llength(n),
lmap(n), lpop(n), lrange(n), lremove(n), lreplace(n),
lreverse(n), lsearch(n), lset(n), lsort(n)
.SH KEYWORDS
element, index, list
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