CODEWITHSUNDEEP
c++if-statementwhile-loopc++17c++20
tsragravorogh
tsragravorogh

Reputation: 3153

Why we can have a semicolon in if but not in while loop

Why can I do this:

if (int result=getValue(); result > 100) {
}

but cannot do this:

while (int result=getValue(); result > 100) {
}

Why discriminate against while? A condition is a condition. Why while cannot evaluate it like if can?

In order to achieve the desired behavior with while, I'd have to implement it this this way:

int result = getValue();
while (result > 100) {
    //do something
    result = getValue();
}

Upvotes: 3

Views: 7298

Answers (2)

cigien
cigien

Reputation: 60258

There are 3 reasons I can think of for not adding this syntax.

  1. There is a perfectly suitable construct, namely the for loop, that can be used for exactly this purpose.

  2. Adding any feature to the language is a lot of work, and a very strong case needs to be made for such a proposal. Given the first point, I don't see this happening.

  3. In my opinion this is the most important one: If this feature were added to the language (let's say for a convenient syntax, or something like that), then it can essentially never be removed from the language. This means that the while (;) syntax is forever banned, and there could very well be some other semantics that we would like to express using such a syntax, and giving up this option is not something that should be done without careful thought.

Upvotes: 5

Barry
Barry

Reputation: 303457

Because we already have a while-loop-with-initializer. It's spelled:

for (int result=getValue(); result > 100;) {
}

Upvotes: 18

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