定义C结构时的问题…（又称沮丧）

Question

Hey so I'm simply trying to define a struct. I'm probably being an idiot, but hey, I'm trying.

Doing this:

struct Neuron{
    float mu;
    float stim[10];
    float hist[10];
    int ns[10000];
    float st[10000];
    float cup[8][10];

};


struct Neuron nur1;


nur1.mu = -0.7;

Getting this:

error: unknown type name 'nur1'

I do not understand why this is. It's all in the same .c file. Maybe compilation issues? Simply using gcc my_file.c on mac OS X. <3 <3

Answer 1

You can't just say nur1.mu = -0.7 like that. Try putting it in a function (maybe your main function):

int main()
{
nur1.mu = -0.7;
}

Answer 2

You need to have a main function; otherwise the complier doesn't know where to look for the start of the first function. The struct is declared outside of main() with everything else inside, like this:

struct Neuron{
    float mu;
    float stim[10];
    float hist[10];
    int ns[10000];
    float st[10000];
    float cup[8][10];
};

int main()
{

struct Neuron nur1;

    nur1.mu = -0.7;
    printf("%f\n", nur1.mu);

}

Answer 3

If it's just to initialize the struct properly, you can use an initializer. This is allowed at the file-level (using only a constant expression ), or for a local variable.

struct Neuron nur1 = {
    .mu = -0.7;
};

The syntax like .mu is called designated initializer (C99).

Note this will be performed once during program startup and will also initialize all not explicitly initialized fields to 0 as for any global object (see C11 6.7.9p10 ).