18. Globals

Valid global scope statements include:

• Variable Declarations

• Struct Declarations

• Function and Procedure Declarations

• Function and Procedure Prototypes

• Typealias

All global statements are considered declarations. Global statements may occur in any order, given respective symbols are defined before being referenced.

18.1. Variable Declarations

In Gazprea values can be assigned to a global identifier. All globals must be immutable (const). If a global identifier is declared with the var specifier, then an error should be raised. This restriction is in place since mutable global variables would ruin functional purity. If functions have access to mutable global state then we can not guarantee their purity.

Globals must be initialized with a valid constant expression. A global initializer may therefore reference other globals and use arithmetic and constexpr aggregates, but it must be fully evaluable by the compiler before the program runs. This preserves functional purity and enables compile-time optimizations. As a consequence:

• Functions, procedures, and I/O operations may not appear in a global’s initializer.

• A global may not have a vector type (the dynamically-sized type), because a vector’s size is determined at run time. An inferred-size array such as const integer[*] X = [1, 2, 3] is permitted: [*] denotes an inferred size that is fixed by its constexpr initializer at compile time.

• All globals are implicitly constexpr.