#multiplexer

12 messages · Page 1 of 1 (latest)

full totem
#

How to create a multiplexer using o1js?

slate ether
#

You can use ‘Provable.switch’

full totem
#

How to build the one-hot encoded bool array from UInt32 (the easy way)

marsh otter
#

what is needed here is a decoder.
for example, a 3-bit decoder will take input in the range 0-7 and output a 3-bit vectors
5 => [1,0,1] ; 4 => [1,0,0] ....
and you assert 5 == 4*1 + 2*0 + 1*1 etc
then you can use the switch.

I am not aware of any library support for this. if it already exists.

upbeat shore
#

Could probably use the packed bool class to achieve what @marsh otter is describing.

upbeat shore
# 
import { Field, Provable } from "o1js";
import { PackedBoolFactory } from "o1js-pack";

class EightBits extends PackedBoolFactory(8) {

}

class OneHot extends EightBits {
  static check(value: { packed: Field }): void {
    let countTrue = Field(0)
    const unpacked = OneHot.unpack(value.packed)
    for (let i = 0; i < OneHot.l; i++) {
      const isTrue = Provable.if(
        unpacked[i],
        Field(1),
        Field(0)
      )
      countTrue = countTrue.add(isTrue)
    }
    countTrue.assertEquals(Field(1));
  }
}

const valid = OneHot.fromBooleans([
  false, true, false, false,
  false, false, false, false
])
console.log(valid.toBooleans())
OneHot.check(valid)

const inValid = OneHot.fromBooleans([
  false, true, false, false,
  true, false, false, false
])
console.log(valid.toBooleans())
OneHot.check(inValid)

Sample usage

next cradle
full totem
#

I am checking whether a chess move is valid, here I wanted to select a piece using a provided "id" ,

# 
    const selfPieces=Provable.if(this.whitesMove.getAndAssertEquals(),this.whitePieces.getAndAssertEquals(),this.blackPieces.getAndAssertEquals());
    const oppPieces=Provable.if(this.whitesMove.getAndAssertEquals(),this.blackPieces.getAndAssertEquals(),this.whitePieces.getAndAssertEquals());
    const board=Board.fromEncoded(selfPieces,oppPieces);
    const piece=board.selfPieces[id];
    //verify:
    //piece should not be captured
    piece.captured.assertFalse();
    //piece can move to new position
    piece.canMoveTo(newPosition).assertTrue();
    //1.piece does not capture own piece
    board.selfPieces.forEach((piece) => {
      piece.position.equals(newPosition).assertFalse();
    }, 'piece cannot capture own piece');
    //2.piece does pass through other pieces
    Provable.switch([piece.type], {);
    //3.move does not put own king in check
    

    //update board
    piece.position.set(newPosition);
    let [a,b]=board.encode();
    this.whitePieces.set(a);
    this.blackPieces.set(b);
    this.whitesMove.set(this.whitesMove.get().not());
  }```
full totem
#

@upbeat shore If I want to pack/unpack a field X into arrays is manipulating X as a bigInt better than bool array?

full totem