Pentagram: Difference between revisions

=={{header|Tcl}}==

This implementation draws a simple pentagram on a [http://wiki.tcl.tk/1415 Canvas] widget.

{{works with|Tcl|8.6}}

<lang Tcl>

package require Tk 8.6 ;# lmap is new in Tcl/Tk 8.6

set pi [expr 4*atan(1)]

pack [canvas .c] -expand yes -fill both ;# create the canvas

update ;# draw everything so the dimensions are accurate

set w [winfo width .c] ;# calculate appropriate dimensions

set h [winfo height .c]

set r [expr {min($w,$h) * 0.45}]

set points [lmap n {0 1 2 3 4 5} {

set n [expr {$n * 2}]

set y [expr {sin($pi * 2 * $n / 5) * $r + $h / 2}]

set x [expr {cos($pi * 2 * $n / 5) * $r + $w / 2}]

list $x $y

}]

set points [concat {*}$points] ;# flatten the list

puts [.c create line $points]

;# a fun reader exercise is to make the shape respond to mouse events,

;# or animate it!

</lang>