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6.5 Return Statements

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   A return_statement is used to complete the execution of the innermost enclosing subprogram_body, entry_body, or accept_statement.

Syntax

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return_statement ::= return [expression];

Name Resolution Rules

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   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 corresponding function.

Legality Rules

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   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.
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   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.

Dynamic Semantics

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   For the execution of a return_statement, the expression (if any) is first evaluated and converted to the result subtype.
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   If the result type is class-wide, then the tag of the result is the tag of the value of the expression.
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   If the result type is a specific tagged type:
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    A type is a return-by-reference type if it is a descendant of one of the following:
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    If the result type is a return-by-reference type, then a check is made that the return expression is one of the following:
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    The exception Program_Error is raised if this check fails.
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    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.
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    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

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    Examples of return statements:
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return;                         -- in a procedure body, entry_body, or accept_statement
return Key_Value(Last_Index);   -- in a function body

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