[drawShifted] Shift a path by an absolute value in Asymptote

drawShifted.asy

void drawShifted(
    path g,
    pair trueshift,
    picture pic=currentpicture,
    Label label="",
    pen pen=currentpen,
    arrowbar arrow=None,
    arrowbar bar=None,
    margin margin=NoMargin,
    marker marker=nomarker
) {
    pic.add(new void(frame f, transform t) {
        picture opic;
        draw(
            opic,
            L=label,
            shift(trueshift) * t * g,
            p=pen,
            arrow=arrow,
            bar=bar,
            margin=margin,
            marker=marker
        );
        add(f, opic.fit());
    });
    pic.addBox(min(g), max(g), trueshift + min(pen), trueshift + max(pen));
}

// Examples
// drawshifted((x,barheight) -- (x+dx, barheight), trueshift=barshifty, label=dxlabel, bar=Bars);
// drawshifted((barx,0) -- (barx, f(x)), trueshift=barshiftx, label=fxlabel, arrow=Arrows(), bar=Bars);