begintemplate Gap
public src, target, g, valid, pr, set_gm, gm, cm
objref srcsec, targetsec, cm, gm, y, b, xvec, sl, lm, this, fih
strdef tstr

proc init(){
    g_     = 10
    valid_ = 0
    cm     = new Matrix(2,2,2)
    gm     = new Matrix(2,2)
    y      = new Vector(2)
    b      = new Vector(2)
    xvec   = new Vector(2)
}

func src() {
    srcsec = new SectionRef()
    xvec.x[0] = $1
    valid_ = 0
    return valid()
}

func target() {
    targetsec = new SectionRef()
    xvec.x[1] = $1
    valid_ = 0
    return valid()
}

func g() {
    if (numarg() > 0) {
        g_ = $1
        if (valid_) {
            set_gm()
        }
    }
    return g_
}

proc set_gm() { local us, a// conductance in nanosiemens
    if (valid_ == 0) { return }
    us = .001*g_
    srcsec.sec { a = 100/area(xvec.x[0]) }
    gm.x[0][0] = us*a
    gm.x[0][1] = -us*a
    targetsec.sec { a = 100/area(xvec.x[1]) }
    gm.x[1][1] = us*a
    gm.x[1][0] = -us*a
}

func valid() {
    if (valid_ == 0) {
        if (object_id(srcsec) && object_id(targetsec)) {
            mkgap()     
        }
    }
    return valid_
}

proc mkgap() {
    sl = new SectionList()
    srcsec.sec sl.append()
    targetsec.sec sl.append()
    valid_ = 1
    set_gm()
    lm = new LinearMechanism(cm, gm, y, b, sl, xvec)
    // only necessary because we anticpate changes in diameter
    // fih = new FInitializeHandler(0, "set_gm()")
    // unfortunately up through the  5.6 2004/02/09 Main (44)
    // version there is an error in parsing the third arg, so
    sprint(tstr, "%s.set_gm()", this)
    fih = new FInitializeHandler(0, tstr)
}

proc pr() {
    if (valid_) {
srcsec.sec printf("%s %s(%g)", this, secname(), xvec.x[0])
targetsec.sec printf("---%s(%g) \tg = %g (ns)\n", secname(), xvec.x[1], g())
    }else{
        printf("%s not used\n", this)
    }
}
endtemplate Gap