ethereum.forks.byzantium.vm.instructions.comparison

Ethereum Virtual Machine (EVM) Comparison Instructions.

.. contents:: Table of Contents :backlinks: none :local:

Introduction

Implementations of the EVM Comparison instructions.

less_than

Checks if the top element is less than the next top element. Pushes the result back on the stack.

Parameters

evm : The current EVM frame.

def less_than(​evm: Evm​) -> None:
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    """
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    Checks if the top element is less than the next top element. Pushes the
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    result back on the stack.
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    Parameters
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    ----------
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    evm :
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        The current EVM frame.
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    """
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    # STACK
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    left = pop(evm.stack)
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    right = pop(evm.stack)
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    # GAS
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    charge_gas(evm, GAS_VERY_LOW)
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    # OPERATION
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    result = U256(left < right)
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    push(evm.stack, result)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

signed_less_than

Signed less-than comparison.

Parameters

evm : The current EVM frame.

def signed_less_than(​evm: Evm​) -> None:
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    """
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    Signed less-than comparison.
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    Parameters
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    ----------
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    evm :
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        The current EVM frame.
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    """
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    # STACK
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    left = pop(evm.stack).to_signed()
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    right = pop(evm.stack).to_signed()
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    # GAS
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    charge_gas(evm, GAS_VERY_LOW)
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    # OPERATION
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    result = U256(left < right)
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    push(evm.stack, result)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

greater_than

Checks if the top element is greater than the next top element. Pushes the result back on the stack.

Parameters

evm : The current EVM frame.

def greater_than(​evm: Evm​) -> None:
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    """
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    Checks if the top element is greater than the next top element. Pushes
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    the result back on the stack.
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    Parameters
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    ----------
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    evm :
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        The current EVM frame.
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    """
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    # STACK
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    left = pop(evm.stack)
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    right = pop(evm.stack)
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    # GAS
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    charge_gas(evm, GAS_VERY_LOW)
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    # OPERATION
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    result = U256(left > right)
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    push(evm.stack, result)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

signed_greater_than

Signed greater-than comparison.

Parameters

evm : The current EVM frame.

def signed_greater_than(​evm: Evm​) -> None:
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    """
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    Signed greater-than comparison.
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    Parameters
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    ----------
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    evm :
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        The current EVM frame.
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    """
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    # STACK
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    left = pop(evm.stack).to_signed()
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    right = pop(evm.stack).to_signed()
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    # GAS
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    charge_gas(evm, GAS_VERY_LOW)
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    # OPERATION
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    result = U256(left > right)
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    push(evm.stack, result)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

equal

Checks if the top element is equal to the next top element. Pushes the result back on the stack.

Parameters

evm : The current EVM frame.

def equal(​evm: Evm​) -> None:
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    """
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    Checks if the top element is equal to the next top element. Pushes
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    the result back on the stack.
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    Parameters
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    ----------
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    evm :
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        The current EVM frame.
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    """
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    # STACK
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    left = pop(evm.stack)
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    right = pop(evm.stack)
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    # GAS
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    charge_gas(evm, GAS_VERY_LOW)
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    # OPERATION
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    result = U256(left == right)
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    push(evm.stack, result)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)

is_zero

Checks if the top element is equal to 0. Pushes the result back on the stack.

Parameters

evm : The current EVM frame.

def is_zero(​evm: Evm​) -> None:
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    """
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    Checks if the top element is equal to 0. Pushes the result back on the
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    stack.
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    Parameters
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    ----------
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    evm :
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        The current EVM frame.
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    """
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    # STACK
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    x = pop(evm.stack)
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    # GAS
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    charge_gas(evm, GAS_VERY_LOW)
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    # OPERATION
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    result = U256(x == 0)
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    push(evm.stack, result)
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    # PROGRAM COUNTER
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    evm.pc += Uint(1)