CODEWITHSUNDEEP
c
Dave
Dave

Reputation: 1208

Trouble with complex numbers in C

I have a larger piece of code (I didn't write it) that makes use of complex numbers defined through a structure. I need to edit it and simply multiply a complex number by a real but cant seem to get it right. I keep getting the following error message. 

error: invalid operands to binary * (have ‘cplx’ and ‘double’)

I know this could be done using the complex.h library but that would mean a lot of rewriting so is there a simpler way? The code below reproduces my problem.

#include <stdio.h>
#include <math.h>

typedef struct cplxS {
    double re;
    double im;
} cplx;

int main()
{   
    double a = 1.3;
    cplx b = {1, 2};
    c = a * b;
}

Upvotes: 1

Views: 499

Answers (2)

Miket25
Miket25

Reputation: 1903

You will first have to initialize a node using malloc

 #include <stdlib.c>

 int main(){   
    double a = 1.3;

    //initialize struct
    struct cplxS* b = malloc(sizeof(struct cplxS));

    //set values for b
    b->re = 1;
    b->im = 2;

    //preform your multiplication
    double c = a*(b->re); //value c with re
    double d = a*(b->im); //value d with im

    //free node memory 
    free(b);
    b = NULL;
}

If you want to update the struct by multiplying c to its values, it would follow

 #include <stdlib.c>

 int main(){   
    double a = 1.3;

    //initialize struct
    struct cplxS* b = malloc(sizeof(struct cplxS));

    //set values for b
    b->re = 1;
    b->im = 2;

    //preform your multiplication
    b->re = a*(b->re); //update b with a*re
    b->im = a*(b->im); //value b with a*im

    //free node memory 
    free(b);
    b = NULL;
}

Hope this helps!

Upvotes: 1

David Manheim
David Manheim

Reputation: 2626

You need to either cast the double as a complex number, and use the complex multiplication function (which presumably exists, or could/should be written by overloading * operator)

int main()
{   
    double a = 1.3;
    cplx a_c = {1.3, 0}
    cplx b = {1, 2};
    c = a_c * b;
}

or actually perform the multiplication, either by building a definition for multiplication of reals and complex numbers (not shown), or just doing it yourself.

int main()
{   
    double a = 1.3;
    cplx b = {1, 2};
    cplx c = {b.re*a, b.im*a};
}

Upvotes: 0

Related Questions