1 
#ifndef FOO_H
#define FOO_H

struct Foo{
  int randInt = random(0, 101);
};

#endif

I have a header file with a struct like above but when I compile I get this error:

'random' was not declared in this scope

How can I use random() in a header file?

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2 Answers 2

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2

Add #include <Arduino.h> like this

#ifndef FOO_H
#define FOO_H

#include <Arduino.h>

struct Foo{
  int randInt = random(0, 101);
};

#endif
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2

The struct is a declaration of a type. You cannot mix it with the initialization. This is how it could be:

In foo.h:

#ifndef FOO_H
#define FOO_H

struct Foo{
  int randInt;
};

extern struct Foo foo;
struct Foo *initFoo(struct Foo *foo_ptr);
#endif

In foo.c:

#include "foo.h"

struct Foo foo;
struct Foo *initFoo(struct Foo *foo_ptr) {
  if (!foo_ptr)
    return NULL;
  foo_ptr->randInt = random(0, 101);
  return foo_ptr;
}

random() is a function and therefore its return value cannot be used as static initializer. Unless -std=c++11 or -std=gnu++11 are enabled.

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6
  • It's valid C++ code I don't see why it would be different for an Arduino. The code works fine after I #include <Arduino.h>. Commented Oct 19, 2015 at 23:16
  • What is the outcome? Did you try to compile exactly the code you put in your question? Commented Oct 19, 2015 at 23:23
  • I answered my question and it works as is. The only problem was that random() was defined in my header file so I had to include the Arduino library. Someone commented for me to do but it's gone now, I guess they deleted it. Commented Oct 19, 2015 at 23:27
  • With gcc, it works only with -std=c++11 or -std=gnu++11. Probably the Arduino ide turns them on by default. Commented Oct 19, 2015 at 23:31
  • 1
    Arduino does in fact have -std=gnu++11 by default Commented Oct 20, 2015 at 4:54

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