- A return_statement is used to complete the execution of the innermost
enclosing subprogram_body, entry_body, or accept_statement.
return_statement ::= return [expression];
Name Resolution Rules
- The expression, if any, of a return_statement is called the return
expression. The result subtype of a function is the subtype denoted by the
subtype_mark after the reserved word return in the profile of the function.
The expected type for a return expression is the result type of the
- A return_statement shall be within a callable construct, and it applies
to the innermost one. A return_statement shall not be within a body that is
within the construct to which the return_statement applies.
- A function body shall contain at least one return_statement that applies
to the function body, unless the function contains code_statements. A
return_statement shall include a return expression if and only if it applies
to a function body.
- For the execution of a return_statement, the expression (if any) is first
evaluated and converted to the result subtype.
- If the result type is class-wide, then the tag of the result is the tag
of the value of the expression.
- If the result type is a specific tagged type:
- If it is limited, then a check is made that the tag of the value
of the return expression identifies the result type.
Constraint_Error is raised if this check fails.
- If it is nonlimited, then the tag of the result is that of the
- A type is a return-by-reference type if it is a descendant of one of the
- a task or protected type;
- a nonprivate type with the reserved word limited in its
- a composite type with a subcomponent of a return-by-reference
- a private type whose full type is a return-by-reference type.
- If the result type is a return-by-reference type, then a check is made
that the return expression is one of the following:
- a name that denotes an object view whose accessibility level is
not deeper than that of the master that elaborated the function
- a parenthesized expression or qualified_expression whose operand
is one of these kinds of expressions.
- The exception Program_Error is raised if this check fails.
- For a function with a return-by-reference result type the result is
returned by reference; that is, the function call denotes a constant view of
the object associated with the value of the return expression. For any other
function, the result is returned by copy; that is, the converted value is
assigned into an anonymous constant created at the point of the return_statement, and the function call denotes that object.
- Finally, a transfer of control is performed which completes the
execution of the callable construct to which the return_statement applies,
and returns to the caller.
- Examples of return statements:
return; -- in a procedure body, entry_body, or accept_statement
return Key_Value(Last_Index); -- in a function body
-- Email comments, additions, corrections, gripes, kudos, etc. to:
Magnus Kempe -- Magnus.Kempe@di.epfl.ch
Page last generated: 95-03-12