math.tcl

#! /usr/bin/wish

package require Tk
tk scaling [expr {240/72}]
canvas  .cv -width 180m -height 270m  -bg white
pack   .cv
set font {Arial 24}
set l .label0
label $l -bd 0 -padx 0 -pady 0 -highlightthickness 0 -font $font -text "0"
set zero_width  [expr { 1.3 * [winfo reqwidth  $l]}]
set zero_height [expr { 1.4 * [winfo reqheight $l]}]
destroy $l

set page_width  [.cv cget -width]
set page_height [.cv cget -height]

proc one_equation {x y} {
    global font
    global zero_width
    global zero_height
    if { floor(2 * rand()) == 0 } {
        set sign "+"
    } else {
        set sign "-"
    }
    if { $sign == "-" } {
        set a [expr {1 + int(20 * rand ())}]
        set b [expr {1 + int(($a - 1) * rand())}]
    } else {
        set a [expr {int(20 * rand ())}]
        set b [expr {1 + int( (19 - $a) * rand())}]
    }
    set textid [.cv create text $x $y -text "$a $sign $b" -font $font -anchor nw]
    set bb [.cv bbox $textid]
    set bw [expr {[lindex $bb 2] - [lindex $bb 0]}]
    set iw [expr {7 * $zero_width}]
    set nx [expr {[lindex $bb 0] + ($iw - $bw) / 2}]
    .cv coords $textid $nx $y
    .cv create text [expr {$x + 6 * $zero_width}] $y -text "=" -font $font -anchor nw
}


for {set col 0} {$col < $page_width} {set col [expr {$col + $page_width/3}]} {
    for {set row [expr {$zero_height/2}]} {$row < $page_height - $zero_height / 2} {set row [expr {$row + $zero_height}]} {
        one_equation $col $row
    }
}

update
.cv postscript -file "m.ps"