Constants

A constant gives a name to a value known while the program is compiled:

namespace Limits

public const MaximumAttempts: Int = 3
const Greeting = "Welcome"

Constants live at namespace scope. Their names can be used by later declarations and executable code:

function main()
    print(Greeting)
    print(MaximumAttempts)
end

The type annotation is optional when Pop can determine the type from the initializer. Writing it can make a public constant’s contract clearer.

Unlike a local variable, a constant cannot be assigned a new value. Its initializer must be a compile-time expression; it cannot depend on command-line input, mutable state, runtime allocation, or an ordinary runtime-only function.

Compile-time evaluation uses the same checked numeric rules as executable code. Integer overflow, division by zero, invalid calls, and evaluation cycles are diagnosed during compilation rather than deferred to the finished program.

Constants are useful for shared limits, fixed labels, attribute arguments, and record or class field defaults. Prefer a local when the value belongs to one execution of a function, even if that local is never reassigned.