control structure
repeat over shelf-name (as alias)? (& shelf-name (as alias)?)* local-declaration* action* again
You can use repeat over
to process each item on a shelf in turn. The following program creates a shelf with five items and outputs each item in turn:
process local integer digits initial {1,2,3,4,5} repeat over digits & letters output "d" % digits || "%n" again
Within the body of the repeat over
loop, the current item on the shelf is advanced one position for each iteration of the loop. This means that you can refer to the current item by the name of the shelf alone, without an indexer, as in the example above. You can still reference other items on the shelf using indexers.
You can repeat over more that one shelf at a time, providing that all the shelves are the same size:
process local integer digits initial {1,2,3,4,5} local stream letters initial {"A", "B", "C", "D", "E"} repeat over digits & letters output letters || "d" % digits || "%n" again
Within a repeat over
loop, three built in variable are available to help you determine which iteration is being executed. #first and #last are switch variables that return true when the loop is in the first and last iterations respectively:
process local integer digits initial {1,2,3,4,5} local stream letters initial {"A", "B", "C", "D", "E"} repeat over digits & letters output "[" when #first output letters || "d" % digits output ", " unless #last output "]%n" when #last again
#item
returns an integer corresponding to the number of iterations of the loop, starting at 1 (one):
process local stream letters initial {"A", "B", "C", "D", "E"} repeat over letters output "[" when #first output letters || "d" % #item output ", " unless #last output "]%n" when #last again
You can specify an alias for the shelf that you are repeating over. The alias name is specified using the as
keyword following the name of the shelf. Specifying an alias is required when you iterate over a shelf that is a field of a record:
declare record foo field stream letters initial {"A", "B", "C", "D", "E"} process local foo x repeat over x:letters as letters output "[" when #first output letters || "d" % #item output ", " unless #last output "]%n" when #last again
A using
statement inside a repeat over loop will reset the current item to that specified in the using
but will not affect the sequence or number of iterations.
You can add an item to a shelf inside a repeat over loop, but only at a position greater that the size of the shelf when the loop began. The number of iterations in the loop is determined before the first iteration, and adding more items to the shelf from within the loop will not change the number of iterations being performed. You can remove items from a shelf within a repeat over loop, but only items that were added within the same loop.
repeat over
can also be used to process the following:
repeat over attribute
and repeat over data-attribute
repeat over attributes
and repeat over data-attributes
repeat over current elements
repeat over referents
repeat over xml-dtds
and repeat over sgml-dtds