Loop statement

 

LoopStatement ::= 
    "FOR" Ident "IN" LoopSetDefinition 
    "DO" StatementList "END" |
    "FOR" "IN" LoopSetDefinition 
    "DO" StatementList "END" 
LoopSetDefinition ::= 
    Expression ".." Expression |
    Expression

    A RainCode loop statement repeats the execution of a statement list for all values of a free variable taken from a reference set. This free variable does not have to be defined prior to the loop. If the free variable's identifier is not defined (second form in the grammar presented above), the predefined anonymous identifier X is to be used.

Hence, a statement such as:

FOR IN 1..10 DO
  OUT.WriteLn(X);
  END;

is equivalent to:

FOR X IN 1..10 DO
  OUT.WriteLn(X);
  END;

The reference set can be of two forms:

• It can be defined by two integer expressions, yielding an integer interval. The free variable successively takes all the integer values within the interval. If the second expression lies under the first expression, the interval is empty, and the statement list is not executed at all, as in 7..2.
• It can be defined as a single expression, that must denote a list. The free variable successively takes all the values in this reference list. If the reference list is empty, the statement list is not executed at all.