Method add

bitvm/src/bigint/add.rs:37–64

Compute the sum of two BigInts

(a: u32, b: u32)

    /// Compute the sum of two BigInts
    pub fn add(a: u32, b: u32) -> Script {
        script! {
            { Self::zip(a, b) }

            { 1 << LIMB_SIZE }

            // A0 + B0
            limb_add_carry OP_TOALTSTACK

            // from     A1      + B1        + carry_0
            //   to     A{N-2}  + B{N-2}    + carry_{N-3}
            for _ in 0..Self::N_LIMBS - 2 {
                OP_ROT
                OP_ADD
                OP_SWAP
                limb_add_carry OP_TOALTSTACK
            }

            // A{N-1} + B{N-1} + carry_{N-2}
            OP_NIP
            OP_ADD
            { limb_add_nocarry(Self::HEAD_OFFSET) }

            for _ in 0..Self::N_LIMBS - 1 {
                OP_FROMALTSTACK
            }
        }
    }

    /// add one
    pub fn add1() -> Script {