swapn-dupn.md

Parameters

• DUPN_OPCODE = 0xE6
• SWAPN_OPCODE = 0xE7

Instructions

Upon activation of this EIP, introduce two new instructions SWAPN and DUPN, both with an immediate operand n ∈ [17, 235].

• SWAPN n:
• DUPN n:

Encoding

Each instruction spans 2 bytes. The first byte is either SWAPN_OPCODE or DUPN_OPCODE. The second byte is f(n) as defined by the following Python code:

def f(n: int) -> int:
    assert 17 <= n <= 235
    y = n - 17
    if y < 0x5B:
        return y
    else:
        return y - 0x5B + 0x80