Creating const data

[Andrew Chalk]

I have a variable that is initialized with a value read from a configuration
file. Once initialized, it should not be changed anywhere in my program.
What is the best way to enforce this (it should be treated as const)?
Ideally, I would like a violation to generate a compile-time error.

Many thanks.

 

[Ian Collins]

I have a variable that is initialized with a value read from a configuration
file. Once initialized, it should not be changed anywhere in my program.
What is the best way to enforce this (it should be treated as const)?
Ideally, I would like a violation to generate a compile-time error.

Use a const member of a class or struct:

struct X {
const int value;

X( int v ) : value(v) {}
};

X constants( whatEver );

 

[Alf P. Steinbach]

* Andrew Chalk:

I have a variable that is initialized with a value read from a configuration
file. Once initialized, it should not be changed anywhere in my program.
What is the best way to enforce this (it should be treated as const)?
Ideally, I would like a violation to generate a compile-time error.

In addition to Ian Collins' reply, you can do

Type const myVariable = valueFromConfigFile();

which for purposes of handling exceptions etc. you can put inside a
function, with lazy initialization (singleton pattern)

Type const& value()
{
static Type const theValue = valueFromConfigFile();
return theValue;
}