Scope

The scope of an identifier is the lexical range of a program throughout which the identifier means a particular type of, or instance of, an object. The same identifier can be associated with several different objects in different parts of the same program.

The names of members of an adt occupy a separate, nonconflicting space from other identifiers; they are declared in a syntactically distinct position, and are always used in a distinguishable way, namely after the . selection operator. Although the same scope rules apply to adt members as to other identifiers, their names can coincide with other entities in the same scope.

Similarly, the names of constants, functions, data objects, and types appearing within a module declaration are ordinarily qualified either with the name of the module or with a module variable using the -> notation. As discussed above, the import declaration lifts these names into the current scope.

Identifiers declared in a top-declaration (see above) have scope that lasts from the declaration throughout the remainder of the file in which it occurs, unless it is overridden by a redeclaration of that name within an inner scope. Each function definition, and each block within a function, introduces a new scope region. A name declared within the block or function (including a formal argument name of a function) has a scope that begins at the completion of its declaration and lasts until the end of the block or function. If an already-declared identifier is redeclared within such an inner scope, the declaration previously in force is used in any initialization expression that is part of the new declaration.

As discussed above, within case and alt, each qualifier and the statements following it form an inner scope just like a block.

The scope of a label is restricted to the labelled statement, and label names can coincide with those of other entities in the same scope.