How to remove negation in if block?-CodePudding

Followed the do..while pattern recommended here:

for {
    work()
    if !condition {
        break
    }
}

Below code is implementing do..while(condition) using for loop:

var r *s
var err error
counter := 0

for { // do..while(specificerror && < MAX && trigger_not_initiated)

    r, err = f()
    counter = counter   1
    if !(err != nil &&
        strings.Contains(err.Error(), "specificerror") &&
        counter < MAX &&
        !IsTriggerInitiated()) {
        break
    }
}

But review team suggests to make if condition more readable by removing negation in negation(condition) in if statement

How to remove negation in negation(condition) for if statement?

CodePudding user response：

The transformation you need is called De Morgan's Laws:

not (A or B) = (not A) and (not B)

not (A and B) = (not A) or (not B),

So if you have a statement like this:

if !(a && b && c) {}

It is equivalent to

if !a || !b || !c {}

In your example:

if !(err != nil &&
    strings.Contains(err.Error(), "specificerror") &&
    counter < MAX &&
    !IsTriggerInitiated()) {
    break
}

Translated version:

if err == nil ||
    !strings.Contains(err.Error(), "specificerror") ||
    counter >= MAX ||
    IsTriggerInitiated() {
    break
}

One thing that needs to be inspected: short-circuit evaluation. In a series of && if an expression is evaluated to false, the rest will not be evaluated (we know the result is false).

Luckily, this will remain the same in the translated version: short-circuit evaluation will be the same, because in a series of || if an expression is evaluated to true, the rest will not be evaluated (we know the result is true). So when in the original form a is false, that's exactly the same case when !a is true in the transformed form.

CodePudding user response：

How to remove negation in negation(condition) for if statement?

Exactly as suggested ("use ||")

if !(a && b)

is equivalent to

if !a || !b

For more information, see De Morgan's laws.