qsort with array of structs?

Question

I am trying to use qsort on an array of structs but I get this error: expected primary-expression before '*' token

struct muchie {
    int x,y,c;
} a[100];

int cmp(const void* p, const void* q)
{
    muchie vp,vq;
    vp=*(muchie* p);
    vq=*(muchie* q);
    return vp.c-vq.c;
}

// ....

qsort(a,m,sizeof(muchie),cmp);

Provide correct cast operators: (muchie*)

πάντα ῥεῖ
– πάντα ῥεῖ

2016-01-16 15:25:55 +00:00
Commented Jan 16, 2016 at 15:25 — πάντα ῥεῖ
– πάντα ῥεῖ, Commented Jan 16, 2016 at 15:25
Just use std::sort, that's what it's for.

Cheers and hth. - Alf
– Cheers and hth. - Alf

2016-01-16 15:42:56 +00:00
Commented Jan 16, 2016 at 15:42 — Cheers and hth. - Alf
– Cheers and hth. - Alf, Commented Jan 16, 2016 at 15:42

Danny_ds · Accepted Answer · 2016-01-16 15:36:47Z

1

The casting of the parameters is wrong - should be *(muchie*)p instead of *(muchie* p).

Use:

int cmp(const void* p, const void* q)
{
    muchie vp,vq;
    vp=*(muchie*) p;
    vq=*(muchie*) q;
    return vp.c-vq.c;
}

answered Jan 16, 2016 at 15:36

Danny_ds

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2 Comments

Toma Radu-Petrescu Over a year ago

Oh, boy! Thanks a lot for pointing that out! I've been staring at the screen for a while!

Danny_ds Over a year ago

@rptoma - No problem, glad to help.

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