Macro definition 1

[powerb23]

Hi,
I would like to define a macro that returns 0 if it cannot open the file and returns 1 if it opens the file.

For example;

#define OPEN(fileHandle) (fileHandle = fopen("blah.dat", "r&quot)

I would like to use conditional logic but not sure of how to go around it. In this case, the return value of OPEN(fileHandle) would be 0 or 1

Your help will be appreciated.

 

[Salem]

Since you don't parameterise the rest of the macro (eg, the filename), it seems to me to be obfuscating the code more than it it helpful.

But anyway,

#define OPEN(fileHandle) ( (fileHandle = fopen("blah.dat", "r")) != NULL )

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[powerb23]

Thanks for the reply.

Your help was really appreciated.

 

[powerb23]

Hi,
I was having problems with how to put a while loop that ignores a line in a macro. I had:

#define IGNORELINE(fileHandle) ( while(c != '\n'){ c = fget(fileHandle);
if(c == EOF) break; })

I however get some errors. I would like to use this using the given macro name.

Your help will be appreciated.

 

[Salem]

Well the blank line in the middle of the #define will do you no good. Each continuation line needs a trailing \, even if there's nothing on it.

> I however get some errors
Since you neither state the errors, or provide a context in which you attempt to use this macro, its hard to say.

But I can't think of anywhere where

( while

is valid syntax.

Why are you writing everything as macros?
Why not use functions.

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[powerb23]

Hi,
it's some homework and i can't figure out how they would do this by passing in only the filename as the parameter. To me, it would seem more logical if i passed in two paramters like this.

#define IGNORELINE(fileHandle,c) ( while(c != '\n'){ c = fget(fileHandle); if(c == EOF) break; })

But i am sure how loops work in a macro. That is something really new to me.


Thanks

 

[Salem]

If you want to code arbitrary code as a single statement, then you do this

#define SOMETHING do { /* code goes here */ } while(0)

So for you, you could start with

#define SOMETHING do { int c; /* your code */ } while(0)

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[powerb23]

Hi Salem,
Many thanks for your help. I really appreciated your help. I got it to work.