Ada 2012 Reference Manual
5.3 If Statements
An if_statement selects for execution at most one of the enclosed sequences_of_statements, depending on the (truth) value of one or more corresponding conditions.
Syntax
if_statement ::=
if condition then
sequence_of_statements
{elsif condition then
sequence_of_statements}
[else
sequence_of_statements]
end if;
if condition then
sequence_of_statements
{elsif condition then
sequence_of_statements}
[else
sequence_of_statements]
end if;
Paragraphs 3 and 4 were deleted.
Dynamic Semantics
For the execution of an if_statement, the condition specified after if, and any conditions specified after elsif, are evaluated in succession (treating a final else as elsif True then), until one evaluates to True or all conditions are evaluated and yield False. If a condition evaluates to True, then the corresponding sequence_of_statements is executed; otherwise, none of them is executed.
Examples
Examples of if statements:
if Month = December and Day = 31 then
Month := January;
Day := 1;
Year := Year + 1;
end if;
Month := January;
Day := 1;
Year := Year + 1;
end if;
if Line_Too_Short then
raise Layout_Error;
elsif Line_Full then
New_Line;
Put(Item);
else
Put(Item);
end if;
raise Layout_Error;
elsif Line_Full then
New_Line;
Put(Item);
else
Put(Item);
end if;
