variables

khomeyni

thanks but: suppose i created a variable x:int x; and then during program i dont use it and at last i want to know if it is initialized or no?for example if a condition occured then it would be initialized else ... and i dont know anything about this condition. i can use some idea as initializing it by infinite value but i want to know how to compiler do it? or is another way for? valhamdolelah.

CPallini

You should initialize a variable as soon as possible in your program. :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

Maximilien

it could checks syntactically if the variable is on the left-hand side of an '=', of if syntactically if follows the syntax of an initializer... for example :

int i;
i = 0;

or

int i(123);

or

class Tata
{
Tata() : m_i(123){};

int m_i;
};

Or there might be other more advanced compiler tricks to keep track of variable assignments...

This signature was proudly tested on animals.

David Crow

If no '=' has been encountered for a given variable during the token-parsing phase, it is assumed to be uninitialized. This is covered in compiler classes, and books such as the dragon book. Keep in mind, though, all variables will have a value regardless of what that value is or where it came from.

"Old age is like a bank account. You withdraw later in life what you have deposited along the way." - Unknown

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

josda1000

How about this. Use a boolean along with the integer. for example: int x; bool xIsInitialized = false; And then, when you do start assigning some value to x, update the boolean to true. I think this is a big waste of time though. You should always have it initialized, possibly to -1 or 0 to show that it hasn't been assigned to yet.

Cedric Moonen

You should change your way of thinking: always initialize your variables. You should never have to test if a variable has been initialized or not.

Cédric Moonen Software developer
Charting control [v2.0] OpenGL game tutorial in C++

Maximilien

voted you down... 1- bad programming practice. 2- twice the danger of doing something stupid .. (change one and forget to change the other)

This signature was proudly tested on animals.

josda1000

Um. Yeah. I know. That's why I didn't suggest it. It was an idea. If you read my second line, I said I didn't suggest it. Next time, make sure you read my whole statement.

khomeyni

in the name of god thanks Maximilien. i don't know it up to now. i have also another question :you said that when we use = compiler knows that a variable is initialized so if it save any data for this?any data to know which variables are initialized if yes where? thanks. valhamdolelah.

David Crow

khomeyni wrote:

i don't know it up to now.

Don't know what?

khomeyni wrote:

i have also another question :you said that when we use = compiler knows that a variable is initialized so if it save any data for this?any data to know which variables are initialized if yes where?

The information you are after is not available via code. It's something that the compiler handles internally.

"Old age is like a bank account. You withdraw later in life what you have deposited along the way." - Unknown

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

khomeyni

hello how it saves that a variable is initialized or no.does it saves any data(where?)?or compiler uses a special method? valhamdolelah.

khomeyni

i don't care about = ,() , ... thanks.but indeed i want to know more ,but as it seem it is deep because of compilers. thanks. valhamdolelah.

David Crow

This is not a basic programming subject, and certainly does not belong in the C/C++ forum. Unless you've written a compiler/parser, or have studied the subject, any answer that you are provided will not make any sense.

"Old age is like a bank account. You withdraw later in life what you have deposited along the way." - Unknown

"Fireproof doesn't mean the fire will never come. It means when the fire comes that you will be able to withstand it." - Michael Simmons

CPallini

Inner details of compilers are secret! :suss: On the serious side: inner details of compilers are secret! :rolleyes: If you are still there, consider that compiler's developers may freely choose the implementation details, provided they fullfill the language specification requirements. Hence different compilers may use different strategies to deal with the same problem. If you are really interested in compiler inner mechanisms, I would suggest to start with some introductory material as, for instance, the excellent classic Wirth's "Compiler Construction", freely available (for instance here [^]). As further reading, you may consider Hanson & Fraser's book "A Retargetable C Compiler: Design and Implementation" (see [^]): since lcc is a real compiler and its sourc code is available, you may have a look at it (well, gcc source code too is available...If you are going to examine it, good luck!). :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

CPallini

josda1000 wrote:

How about this. Use a boolean along with the integer. for example: int x; bool xIsInitialized = false; And then, when you do start assigning some value to x, update the boolean to true.

As it stands it is just an abomination. :)

If the Lord God Almighty had consulted me before embarking upon the Creation, I would have recommended something simpler. -- Alfonso the Wise, 13th Century King of Castile.
This is going on my arrogant assumptions. You may have a superb reason why I'm completely wrong. -- Iain Clarke
[My articles]

khomeyni

in the name of god thanks everybody. i find my answer and thanks for everything. i promise you to don't question any other question that is irrelevant. thanks. valhamdolelah.