Add section about duplicated code to P.3 "Express Intent"

[peno2]

I suggest that a section about duplicated code is added to P.3 "Express Intent".

Duplicated code is a common source of a number of problems. I suggest to just ad a simple example without digging deeper into all issues related to the subject.

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Example

Redundant or duplicated code obscures intent and makes it harder to understand the logic. Avoid duplicated code.

void day(bool workday)    // Bad, duplicated code.
{
    if (workday) {
        breakfast();
        work();
        dinner();   
    }
    else {
        breakfast();
        readABook();
        dinner();
    }
}

void day(bool workday)    // Good, no duplicated code.
{
    breakfast();

    if (workday)
        work();
    else
        readABook();

    dinner();
}

See suggested solution here: P.3, "Duplicated Code"