Setting up functions within structs

Question

I am having trouble understanding how to setup my functions within structs, this may have been covered before but in a slightly different way. Consider the code below written in C++,

//Struct containing useful functions.
typedef struct Instructions{
    void W(float);
    void X(float); 
    void Y(float); 
    void Z(int); 
}instruct;

I have started but defining my struct with these void functions, however i wish to define what each function does in the program lets say,

void Z(int x){
    do something...       
}

Both the struct and the function were defined in the global. My question is would i have to refer to the function(in this case void Z(int x)) as:

void instruct.Z(int x){
    do something...
}

or as i have previously done? Furthermore if there better ways of doing this please let me know.

Do not use C tag for C++ questions. These are different languages. — too honest for this site
– too honest for this site, Commented Dec 1, 2015 at 13:43
This is really basic C++ syntax and should be covered by any good book or tutorial. You might want to start there. — crashmstr
– crashmstr, Commented Dec 1, 2015 at 13:45

MikeCAT · Accepted Answer · 2015-12-01 13:44:50Z

2

I guess you want to use member functions

//Struct containing useful functions.
typedef struct Instructions{
    void W(float);
    void X(float); 
    void Y(float); 
    void Z(int); 
}instruct;

void instruct::Z(int x){ // use :: instead of .
    //do something...
}

or pointer-to-functions

//Struct containing useful functions.
typedef struct Instructions{
    void (*W)(float);
    void (*X)(float); 
    void (*Y)(float); 
    void (*Z)(int); 
}instruct;

void Z1(int x){
    //do something...
}

// in some function definition
instruct ins;
ins.Z = Z1;

answered Dec 1, 2015 at 13:44

MikeCAT

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2 Comments

juanchopanza Over a year ago

There's really no need for that typedef syntax.

Kudzai Over a year ago

Thanks for the reply, your second solution seems intriguing. For that would i then pass an integer(lets say int a= 5;) to Z1 by saying(in your case) ins.Z(a)?

PRIME · Accepted Answer · 2015-12-01 13:43:45Z

0

typedef struct Instructions{
    void W(float);
    void X(float); 
    void Y(float); 
    void Z(int); 
}instruct;

void instruct::Z(int x){
    do something...

}

this is how you have to refer if I understood your question correctly..

answered Dec 1, 2015 at 13:43

PRIME

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Comments

Richard Dally · Accepted Answer · 2015-12-01 13:53:56Z

0

Based on MikeCAT answer, std::function could be used to be more "modern".
Note this requires a C++11 compiler.

Live example

#include <functional>

struct Instructions
{
    std::function<void (float)> W;
    std::function<void (float)> X;
    std::function<void (float)> Y;
    std::function<void (int)> Z;
};

void Z1(int x)
{
}

int main()
{
    Instructions ins;
    ins.Z = Z1;

    return 0;
}

answered Dec 1, 2015 at 13:53

Richard Dally

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