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Full Discussion: Arrays in C++
Top Forums Programming Arrays in C++ Post 302584573 by John Tate on Friday 23rd of December 2011 05:03:25 PM
Old 12-23-2011
Arrays in C++

I've noticed something interesting in C++ programming. I've always done tricky stuff with pointers and references to have functions deal with arrays. Doing exercises again out of a C++ book has shown me an easier way, I didn't even know was there. It's weird to me.

When dealing with arrays, it seems if I pass an array to a function although I cannot return an array - if the array is changed it changes for the whole program. The array is seemingly global. Hence this code works (GCC 4.7)...

Code:
#include <iostream>

using namespace std;

int read_inputs(double inputs[], int capacity) {
    int current_size = 0;
    cout << "Please enter values, Q to quit:"<<endl;
    bool more = true;
    while (more)
    {
        double input;
        cin >> input;
        if (cin.fail()) {
            more = false;
        } else if (current_size < capacity) {
            inputs[current_size] = input;
            current_size++;
        }
    }
    return current_size;
}

void multiply(double values[], int size, double factor)
{
    for (int i = 0; i < size; i++)
    {
        values[i]=values[i] * factor;
    }
}

void print(double values[], int size)
{
    for (int i = 0; i < size; i++)
    {
        if (i > 0) {cout << ", ";}
        cout << values[i];
    }
    cout << endl;
}

int main() {
    const int CAPACITY = 1000;
    double values[CAPACITY];
    int size = read_inputs(values, CAPACITY);
    print(values, size);
    multiply(values, size, 2);
    print(values, size);

    return 0;
}

 

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xpc_array_create(3)					   BSD Library Functions Manual 				       xpc_array_create(3)

NAME
xpc_array_create -- creation and management of XPC arrays SYNOPSIS
#include <xpc/xpc.h> xpc_object_t xpc_array_create(const xpc_object_t *objects, size_t count); void xpc_array_set_value(xpc_object_t array, size_t index, xpc_object_t value); void xpc_array_append_value(xpc_object_t array, xpc_object_t value); xpc_object_t xpc_array_get_value(xpc_object_t array, size_t index); size_t xpc_array_get_count(xpc_object_t array); bool xpc_array_apply(xpc_object_t array, xpc_array_applier_t applier); void xpc_array_set_bool(xpc_object_t array, size_t index, bool value); void xpc_array_set_int64(xpc_object_t array, size_t index, int64_t value); void xpc_array_set_uint64(xpc_object_t array, size_t index, uint64_t value); void xpc_array_set_double(xpc_object_t array, size_t index, double value); void xpc_array_set_date(xpc_object_t array, size_t index, int64_t value); void xpc_array_set_data(xpc_object_t array, size_t index, const void *bytes, size_t length); void xpc_array_set_string(xpc_object_t array, size_t index, const char *value); void xpc_array_set_uuid(xpc_object_t array, size_t index, const uuid_t value); void xpc_array_set_fd(xpc_object_t array, size_t index, int value); void xpc_array_set_connection(xpc_object_t array, size_t index, xpc_connection_t value); bool xpc_array_get_bool(xpc_object_t array, size_t index); int64_t xpc_array_get_int64(xpc_object_t array, size_t index); uint64_t xpc_array_get_uint64(xpc_object_t array, size_t index); double xpc_array_get_double(xpc_object_t array, size_t index); int64_t xpc_array_get_date(xpc_object_t array, size_t index); const void * xpc_array_get_data(xpc_object_t array, size_t index, size_t *length); const uint8_t * xpc_array_get_uuid(xpc_object_t array, size_t index); const char * xpc_array_get_string(xpc_object_t array, size_t index); int xpc_array_get_fd(xpc_object_t array, size_t index); xpc_connection_t xpc_array_get_connection(xpc_object_t array, size_t index); ARRAYS
XPC arrays are collections of XPC objects ordered by index. The index is zero-based. XPC arrays are contiguous, and values must exist at all indexes between zero and the greatest index of the array. A hole in the array can be simulated by using a null object as returned by xpc_null_create(3). CREATION
The xpc_array_create() function returns a newly created array. The caller may optionally provide objects, a C array of XPC object references, to initialize the array. The count is used to specify the size of the C array. If objects is NULL, then count must be zero. If count speci- fies more elements than are actually present in values or if values is NULL and count is non-zero, the behavior is undefined. GETTING AND SETTING VALUES
The xpc_array_append_value() function may be used to append a value to the end of an array. This operation increases the count of the values in the array by one. The value of a specific index in the array may be set using the xpc_array_set_value() function. The value must be non-NULL, and the index must already exist (i.e. less than the count provided at creation or extended through previous append operations). The value at a specific index of an array may be retrieved using the xpc_array_get_value() function. The result of getting a non-existing index (i.e. one that was not specified at creation or through a previous append operation) in undefined. PRIMITIVE GET AND SET FUNCTIONS
Various functions exist for retrieving primitive C and operating system types directly from an array without the need for an intermediate boxed object. See xpc_object(3) for more information. The special XPC_ARRAY_APPEND constant may be used to append a value to the end of the array instead of operating on a specific index. SEE ALSO
xpc_object(3), xpc_objects(3), xpc_dictionary_create(3) Darwin 1 July, 2011 Darwin
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