# -*- tcl -*- tcl.tk//DSL diagram//EN//1.0
set boxwidth [3 cm]
proc achild {args} { arrow <- {*}$args}
proc char {pos x} {
    variable movelength
    move down [expr {0.5*$movelength}]
    box "\"$x\"" textcolor blue
    group {
	text text $pos with nw at [last box nw] textcolor red
    }
}
down
box "Expression 0 4"
achild
box "Factor 0 4"
group {
    achild down left left left left ; down
    box "Term 0 2"
    achild
    box "Number 0 2"
    group {
	achild down left left ; down
	box "Digit 0 0" ; char 0 1
    } ; group {
	achild down
	box "Digit 1 1" ; char 1 2
    } ; group {
	achild down right right ; down
	box "Digit 2 2" ; char 2 0
    }
} ; group {
    achild down down down down down
    box "AddOp 3 3" ; char 3 +
} ; group {
    achild down right right ; down
    box "Term 4 4"
    achild
    box "Number 4 4"
    achild down 
    box "Digit 4 4" ; char 4 5
}
line stroke 2 dotted \
    from [0.25 between [6th  box nw] [5th box sw ]] \
    to   [0.25 between [last box ne] [2nd last box se]]