# -*- tcl -*- tcl.tk//DSL diagram//EN//1.0
proc mark {at args} {
    circle radius 2 at $at color red {*}$args
}
proc vector {p args} {
    set e [arrow from [0 0] to $p ]
    mark [last arrow end] {*}$args 
    return $e
}

mark [0 0] "\[0 0\]" anchor se
vector [by 50 se] "\[by 50 se\]" anchor sw
vector [by 100 20] "\[by 100 20\]" anchor nw