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Thinking in C++
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static array initialization

Chapter 8 introduced the static const variable that allows you to define a constant value inside a class body. It’s also possible to create arrays of static objects, both const and non-const. The syntax is reasonably consistent:

//: C10:StaticArray.cpp
// Initializing static arrays in classes
class Values {
  // static consts are initialized in-place:
  static const int scSize = 100;
  static const long scLong = 100;
  // Automatic counting works with static arrays.
  // Arrays, Non-integral and non-const statics 
  // must be initialized externally:
  static const int scInts[];
  static const long scLongs[];
  static const float scTable[];
  static const char scLetters[];
  static int size;
  static const float scFloat;
  static float table[];
  static char letters[];

int Values::size = 100;
const float Values::scFloat = 1.1;

const int Values::scInts[] = {
  99, 47, 33, 11, 7

const long Values::scLongs[] = {
  99, 47, 33, 11, 7

const float Values::scTable[] = {
  1.1, 2.2, 3.3, 4.4

const char Values::scLetters[] = {
  'a', 'b', 'c', 'd', 'e',
  'f', 'g', 'h', 'i', 'j'

float Values::table[4] = {
  1.1, 2.2, 3.3, 4.4

char Values::letters[10] = {
  'a', 'b', 'c', 'd', 'e',
  'f', 'g', 'h', 'i', 'j'

int main() { Values v; } ///:~

With static consts of integral types you can provide the definitions inside the class, but for everything else (including arrays of integral types, even if they are static const) you must provide a single external definition for the member. These definitions have internal linkage, so they can be placed in header files. The syntax for initializing static arrays is the same as for any aggregate, including automatic counting.

You can also create static const objects of class types and arrays of such objects. However, you cannot initialize them using the “inline syntax” allowed for static consts of integral built-in types:

//: C10:StaticObjectArrays.cpp
// Static arrays of class objects
class X {
  int i;
  X(int ii) : i(ii) {}

class Stat {
  // This doesn't work, although 
  // you might want it to:
//!  static const X x(100);
  // Both const and non-const static class 
  // objects must be initialized externally:
  static X x2;
  static X xTable2[];
  static const X x3;
  static const X xTable3[];

X Stat::x2(100);

X Stat::xTable2[] = {
  X(1), X(2), X(3), X(4)

const X Stat::x3(100);

const X Stat::xTable3[] = {
  X(1), X(2), X(3), X(4)

int main() { Stat v; } ///:~

The initialization of both const and non-const static arrays of class objects must be performed the same way, following the typical static definition syntax.

Thinking in C++
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   Reproduced courtesy of Bruce Eckel, MindView, Inc. Design by Interspire