CODEWITHSUNDEEP
c++carrays
veta
veta

Reputation: 736

set array indexes many at once? compound literals?

index = {27,27,27,27,27}; //as many as rootsize

Compiler gives me an error when I try this in a function. Index is globally initialized in the same file with:

int index[5];

error: expected expression index = {27,27,27,27,27}; //as many as rootsize

Is this not legal? How would I set an array to some values all at once? Would I need a loop?

Upvotes: 1

Views: 202

Answers (4)

Vlad from Moscow
Vlad from Moscow

Reputation: 311078

In C++ you can use standard class std::array declared in header <array>.

For example

#include <array>

//...

std::array<int, 5> index;

//...

index = { 27, 27, 27, 27, 27 };

Otherwise you can use for example standard algorithms std::fill or std::fill_n declared in header <algorithm> to fill the array with a value.

For example

#include <algorithm>
#include <iterator>

//...

int index[5];

//...

std::fill( std::begin( index ), std::end( index ), 27 );
// or
std::fill( index, index + 5, 27 );

Or

#include <algorithm>

//...

int index[5];

//...

std::fill_n( index, 5, 27 );

In C you can also enclose the array in a structure and use a compound literal. For example

struct array_t 
{ 
    int index[5]; 
} a;

//...

a = ( struct array_t ){ { 27, 27, 27, 27, 27 } };   

for ( size_t i = 0; i < 5; i++ ) printf( "%i ", a.index[i] );

Of course you can initialize the array when it was declared

int index[5] = { 27, 27, 27, 27, 27 };

Upvotes: 2

caf
caf

Reputation: 239201

You cannot directly assign to an array. You can, however, memcpy() to it from a compound literal:

#include <string.h>

memcpy(index, (int [5]){ 27, 27, 27, 27, 27 }, sizeof index);

Note that compound literals like this are a C feature, but not C++.

Upvotes: 5

Pawan
Pawan

Reputation: 167

Just write int index[5] = {27,27,27,27,27}. and your problem resolved.

Upvotes: 2

Gopi
Gopi

Reputation: 19874

You can't initialize array as you are doing it because array name can't be a modifiable lvalue in C.

int index[5] = {27,27,27,27,27};

is a valid initialization

Upvotes: 2

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