埃菲尔铁塔:有没有办法在埃菲尔铁塔上表达双重隐含子句? [英] Eiffel: is there a way to express a double implies clause in eiffel?

问题描述

就像心理学中的双重约束一样，有没有办法告诉一个表达暗含另一表达呢?

Like double bind in psychology, is there a way to tell that one expression implies another and reversely?

valid_last_error: attached last_error implies not attached last_success_message
valid_last_success_message: attached last_success_message implies not attached last_error

会像

valid_last_error: attached last_error double_binded_not attached last_success_message

可能等同于

valid_last_error: attached last_error never_with attached last_success_message

• T 代表True布尔表达式
• F 为假
• R 作为结果
• T stands for True boolean expression
• F for False
• R for Result

a b R
T T T
T F F
F T T
F F T

和(a，b:BOOLEAN):BOOLEAN

a b R
T T T
T F F
F T F
F F F

或(a，b:BOOLEAN):BOOLEAN

a b R
T T T
T F T
F T T
F F F

xor(a，b:BOOLEAN):BOOLEAN

a b R
T T F
T F T
F T T
F F F

double_implies(a，b:BOOLEAN):BOOLEAN

a b R
T T F
T F T
F T T
F F T

作为一个可能更具解释性的示例(众所周知)，而不是写作

as a maybe more explaining example (more known) instead of writing

invalid_index_implies_off: index < 1 implies off
off_implies_invalid_index: off implies index < 1

我们可以这样写:

index_coherent_with_off: index < 1 never_both off

这只会向BOOLEAN类添加一个函数，例如

which would just add a function to BOOLEAN class such as

alias never_with, alias reversible_implies (v: like Current): like Current
    do
        if Current and v then
            Result := False
        else
            Result := True
        end
    end

希望每个人都明白我的意思...我不知道是否有这样的算术运算符.

Hope now everybody got my point... I don't know if there is such arithmetic operator.

我们可以将其扩展为可变数量的参数

推荐答案

我的问题的唯一答案是在util类之类的函数中定义一个函数

The only answer for my question is to define a function in an util class like

功能-可能在BOOLEAN类中

feature -- could be in class BOOLEAN

double_implies, reversible_implies, never_both (a, b: BOOLEAN): BOOLEAN
        -- Into boolean class with never_with
    do
        if a and b then
            Result := False
        else
            Result := True
        end
    end

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