From Erights

Revision as of 10:31, 18 April 2007 by Mscheffler (Talk)
Jump to: navigation, search

An object declared as, for example

   def foo implements pbc {
       to __optUncall() { return [1, "add", [2]] }
       # ...

will be passed-by-construction across CapTP. This means that its __optUncall() method will be called on the sending side, the elements of the result triple will be passed, and the corresponding triple as received will be called (here, as “, "add", [2])”) to create the object as received.


The first part of the example is a maker for a 2D Vector. The created vectors are Pass By Construction, they should pass the guard :pbc. The method __optUncall is a miranda method. When the vector is copied to another vat, the method __optUncall is called by the CapTP networking subsystem of E. The result of the method is used to recreate the object in the destination vat. This code should be positioned in a file in the java classpath at the location "tests.makeVector.emaker"

def makeVector implements pbc {
    to run(var x, var y) {
        def vector implements pbc {
            to getX() :any { return x }
            to getY() :any { return y }
            to __optUncall() :any { return [makeVector, "run", [x,y]] }
            to __printOn(out) {out.print(`<Vector $x $y>`)}
        return vector
    to __optUncall() :any {
        return [<import>, "get", ["tests.makeVector"]]

Example of usage:

#create a new Vector object
? def makeVector := <import:tests.makeVector&lgt;
# value: <makeVector>

? def vector := makeVector(6.6,7.7)
# value: <Vector 6.6 7.7>

#create a new vat
? introducer.onTheAir()
# value: ["3DES_SDH_M2", "3DES_SDH_M"]

? def seedVatAuthor := <elang:interp.seedVatAuthor>(<unsafe>).virtualize((introducer))
# value: <virtualSeedVat>

# source code for the new vat
? def scriptSource:="def run(thing :pbc) {println(`Thing: $thing`)}"
# value: "def run(thing :near) {println(`Thing: $thing`)}"

? def [scriptObj, vat] := seedVatAuthor(scriptSource)
# value: [<Promise>, <Vat newVirtualSeedVat in <runs in newVirtualSeedVat>>]

? scriptObj <- run(vector)
# value: <Remote Promise>

? Thing: <Vector 6.6 7.7>
Personal tools
more tools