How to avoid while-loop code duplication?

Question

string s = Console.ReadLine();
while(s != null)
{
    // do something 
    //   ....
    s = Console.ReadLine(); 
}

The code above is to get the input, verify it, process it and then input again, but obviously, s = Console.ReadLine(); is code duplication.

What tricks are there to avoid the duplication?

that is the typical pattern of while statement unless you do a while(true) — T McKeown
– T McKeown, Commented Apr 21, 2014 at 13:18
Which language is this? Most support a do-while loop that is useful for situations like this. — ajp15243
– ajp15243, Commented Apr 21, 2014 at 13:18

acushner · Accepted Answer · 2014-04-21 13:18:01Z

2

depending on language, you can often do something like this:

while (s = Console.ReadLine())
{
    ...
}

answered Apr 21, 2014 at 13:18

acushner

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2 Comments

T McKeown Over a year ago

Console.ReadLine() doesn't return a bool

Nacho Over a year ago

This is pretty clearly described as a language agnostic answer. If Java is indeed the target language, then this is pretty easily modified by using while (null != (s = Console.ReadLine()).

chepner · Accepted Answer · 2014-04-21 13:18:05Z

2

In Python (where there is no do-while loop to guaranteed at least one iteration), the trick is to use an infinite loop with an explicit break.

while( true )  // Or whatever evaluates to true unconditionally
{
    s = Console.ReadLine();
    if (s == null) {
        break;
    }
    // do something
}

answered Apr 21, 2014 at 13:18

chepner

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