5.1 Simple and Compound Statements - Sequences of Statements

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A statement is either simple or compound. A simple_statement encloses no other statement. A compound_statement can enclose simple_statements and other compound_statements.


sequence_of_statements ::= statement {statement}

statement ::=
    {label} simple_statement | {label} compound_statement

simple_statement ::= null_statement
   | assignment_statement | exit_statement
   | goto_statement | procedure_call_statement
   | return_statement | entry_call_statement
   | requeue_statement | delay_statement
   | abort_statement | raise_statement
   | code_statement

compound_statement ::=
     if_statement | case_statement
   | loop_statement | block_statement
   | accept_statement | select_statement

null_statement ::= null;

label ::= <<label_statement_identifier>>

statement_identifier ::= direct_name

The direct_name of a statement_identifier shall be an identifier (not an operator_symbol).

Name Resolution Rules

The direct_name of a statement_identifier shall resolve to denote its corresponding implicit declaration (see below).

Legality Rules

Distinct identifiers shall be used for all statement_identifiers that appear in the same body, including inner block_statements but excluding inner program units.

Static Semantics

For each statement_identifier, there is an implicit declaration (with the specified identifier) at the end of the declarative_part of the innermost block_statement or body that encloses the statement_identifier. The implicit declarations occur in the same order as the statement_identifiers occur in the source text. If a usage name denotes such an implicit declaration, the entity it denotes is the label, loop_statement, or block_statement with the given statement_identifier.

Dynamic Semantics

The execution of a null_statement has no effect.

A transfer of control is the run-time action of an exit_statement, return_statement, goto_statement, or requeue_statement, selection of a terminate_alternative, raising of an exception, or an abort, which causes the next action performed to be one other than what would normally be expected from the other rules of the language. As explained in 7.6.1, a transfer of control can cause the execution of constructs to be completed and then left, which may trigger finalization.

The execution of a sequence_of_statements consists of the execution of the individual statements in succession until the sequence_ is completed.


1  A statement_identifier that appears immediately within the declarative region of a named loop_statement or an accept_statement is nevertheless implicitly declared immediately within the declarative region of the innermost enclosing body or block_statement; in other words, the expanded name for a named statement is not affected by whether the statement occurs inside or outside a named loop or an accept_statement -- only nesting within block_statements is relevant to the form of its expanded name.


Examples of labeled statements:

<<Here>> <<Ici>> <<Aqui>> <<Hier>> null;

<<After>> X := 1;

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Copyright © 2000 The MITRE Corporation, Inc. Ada Reference Manual