'\"
'\" 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
.nf
\fBlseq \fIstart \fR?(\fB..\fR|\fBto\fR)? \fIend\fR ??\fBby\fR? \fIstep\fR?
\fBlseq \fIstart \fBcount\fI count\fR ??\fBby\fR? \fIstep\fR?
\fBlseq \fIcount\fR ?\fBby \fIstep\fR?
.fi
.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 "\fB..\fR" or "\fBto\fR" defines the range. The "\fBcount\fR" 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
\fIcount\fR-1.
.PP
The \fBlseq\fR command can produce both increasing and decreasing
sequences. When both \fIstart\fR and \fIend\fR are provided without a
\fIstep\fR value, then if \fIstart\fR <= \fIend\fR, the sequence will be
increasing and if \fIstart\fR > \fIend\fR it will be decreasing. If a
\fIstep\fR 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:
.RS
.PP
.CS \"
% \fBlseq\fR 1 to 5    ;# increasing
\fI\(-> 1 2 3 4 5

% \fBlseq\fR 5 to 1    ;# decreasing
\fI\(-> 5 4 3 2 1

% \fBlseq\fR 6 to 1 by 2   ;# decreasing, step wrong sign, empty list

% \fBlseq\fR 1 to 5 by 0   ;# all step sizes of 0 produce an empty list
.\"
.CE
.RE
.PP
The numeric arguments, \fIstart\fR, \fIend\fR, \fIstep\fR, and \fIcount\fR,
may also be a valid expression. The expression will be evaluated and the
numeric result will be used.  An expression that does not evaluate to a number
will produce an invalid argument error.
.PP
\fIStart\fR defines the initial value and \fIend\fR defines the limit, not
necessarily the last value. \fBlseq\fR produces a list with \fIcount\fR
elements, and if \fIcount\fR is not supplied, it is computed as:
.RS
.PP
.CS
\fIcount\fR = int( (\fIend\fR - \fIstart\fR + \fIstep\fR) / \fIstep\fR )
.CE
.RE
.PP
The numeric arguments, \fIstart\fR, \fIend\fR, \fIstep\fR, and \fIcount\fR,
can also be a valid expression. the \fBlseq\fR command will evaluate the
expression (as if with \fBexpr\fR)
and use the numeric result, or return an error as with any invalid argument
value; a non-numeric expression result will result in an error.
.SH EXAMPLES
.CS
.\"
\fBlseq\fR 3
\fI\(-> 0 1 2\fR

\fBlseq\fR 3 0
\fI\(-> 3 2 1 0\fR

\fBlseq\fR 10 .. 1 by -2
\fI\(-> 10 8 6 4 2\fR

set l [\fBlseq\fR 0 -5]
\fI\(-> 0 -1 -2 -3 -4 -5\fR

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

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

set i 17
         \fI\(-> 17\fR
if {$i in [\fBlseq\fR 0 50]} { # equivalent to: (0 <= $i && $i <= 50)
    puts "Ok"
} else {
    puts "outside :("
}
\fI\(-> Ok\fR

set sqrs [lmap i [\fBlseq\fR 1 10] { expr {$i*$i} }]
\fI\(-> 1 4 9 16 25 36 49 64 81 100\fR
.\"
.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
'\" Local Variables:
'\" mode: nroff
'\" fill-column: 78
'\" End: