Do is a method associated with collection objects. It iterates over every element
of the list and executes some action. Here is the format:
«listExpression».do { «parameter» ->
«action»
}
Where the quoted components, «listExpression», «parameter» and
«action», are replaced by Grace program elements. «listExpression» is any
expression that evaluates to a list, and «action» is any sequence of Grace
statements.
«parameter» is a fresh variable name, the parameter of the block.
You can use whatever name you wish; the name each is a good one if you can’t
think of soemthing more specific.
The parameter is declared just by writing its name between the opening brace {
and the arrow ->. Normally, «action» will involve the use of «parameter»;
if you don’t use «parameter», ask yourself why you are using do.
The do method acts in exactly the same way as a
for loop;
for compatibility with other languages, Grace also has
for loop,
although do methods are more concise.
Both the for loop and the do method execute a
block of code once for each
element of the collection. That element is bound to the parameter of the block.