simple text plot

set plotsize 7
proc textplot {values} {
    set xvals [lmap {x y} $values {set x}]
    set yvals [lmap {x y} $values {set y}]
    set minx [tcl::mathfunc::min {*}$xvals]
    set miny [tcl::mathfunc::min 0 {*}$yvals]
    set maxx [tcl::mathfunc::max {*}$xvals]
    set maxy [tcl::mathfunc::max {*}$yvals]

    set maxx [expr {$maxx + 1}]
    set maxy [expr {$maxy + 1}]

    # 10x10 grid
    set grid [lrepeat $::plotsize [lrepeat $::plotsize {  }]]

    foreach {x y} $values {
        set gx [expr {int((double($x) - $minx) / (double($maxx) - $minx) * $::plotsize)}]
        set gy [expr {int((double($y) - $miny) / (double($maxy) - $miny) * $::plotsize)}]
        # puts "$gx $gy "
        for {set _y 0} {$_y <= $gy} {incr _y} {
            lset grid $_y $gx "**"
        }
    }

    foreach row [lreverse $grid] {
        puts "|[join $row ""]"
    }
    puts "+[string repeat "--" $::plotsize]"
}