CODEWITHSUNDEEP
c++
sonofzen1
sonofzen1

Reputation: 11

I don't understand how I'm getting out of range errors here

What I want to do is very very simple. Read through a string character by character and write the numbers to a separate string while including a space in between.

Ex. original string: "45+67-32" becomes "45 67 32"

Here's my logic:

while (i < line.length())
{
    char c = line.at(i);

    if (isdigit(c))
    {
        c = line.at(i);
        while (isdigit(c) || c == '.' && i < line.size())
        {
            expression = expression + line.at(i);
            i++;
        }
        expression = expression + ' ';
    }
    i++;
}

Upvotes: 1

Views: 98

Answers (1)

Yksisarvinen
Yksisarvinen

Reputation: 22176

C++ standard mandates a feature called short-circuiting. If a result of logical operation can be determined without evaluating all of the operands, it should be done so. There are two cases when this happens:

  1. In expression a || b (a or b), if a is true then expression must also be true and b is irrelevant,
  2. In expression a && b (a and b), if a is false then expression must also be false and b is irrelevant.

Because of short circuits, c == '.' && i < line.size() is not evaluated as long as isdigit(c) is true. Therefore you never know if you are already outside of the string or not.

You can fix your loop by using short circuits to your advantege:

while (i < line.size() && (isdigit(c) || c == '.'))

Upvotes: 1

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