Is this valid?

[Michael]

Hi i recently came across some code that looked like this which I've never
ever seen before! I appreicate it may be 'c' but is it valid in c++??


//main.c

int main()
{
int a;
int b;
//Get values for a & b;

if(a==1)
{
#include "DoA.c"
}
else
{
#include "DoB.c"
}

// More stuff


return 0;
}


//DoA.c
b =4;


//DoB.c
b=6;



Is this valid? Or just obscure?

 

[Ioannis Vranos]

Hi i recently came across some code that looked like this which I've never
ever seen before! I appreicate it may be 'c' but is it valid in c++??


//main.c

int main()
{
int a;
int b;
//Get values for a & b;

if(a==1)
{
#include "DoA.c"
}
else
{
#include "DoB.c"
}

// More stuff


return 0;
}


//DoA.c
b =4;


//DoB.c
b=6;



Is this valid? Or just obscure?

It is valid.

 

[Matt Wharton]

Hi i recently came across some code that looked like this which I've never
ever seen before! I appreicate it may be 'c' but is it valid in c++??


//main.c

int main()
{
int a;
int b;
//Get values for a & b;

if(a==1)
{
#include "DoA.c"
}
else
{
#include "DoB.c"
}

// More stuff


return 0;
}


//DoA.c
b =4;


//DoB.c
b=6;



Is this valid? Or just obscure?

Yes, it's valid. Yes, it's obscure (and entirely unnecessary in the example
you posted).

-Matt

 

[Michael]

in that case, does #include mean copy contents of file here ( with the
absence of pragma's)?

 

[Jonathan Turkanis]

in that case, does #include mean copy contents of file here ( with the
absence of pragma's)?

It means exactly the same thing as it does when used at the beginning of a file.
The preprocessor knows nothing about control structures such as if ( ) { }else
{ }, and so has no idea that headers are being #include'd in unusual places.

The ability to #include headers in the middle of a block of code is very useful
for preprocess metaprogramming (see
http://boost-consulting.com/tmpbook/preprocessor.html)

Jonathan

 

[Ioannis Vranos]

in that case, does #include mean copy contents of file here ( with the
absence of pragma's)?

#includes are processed by the preprocessor before the compilation. In
the final source code that gets compiled, the #includes have been
replaced by the text that they include.