graph reduction

A technique invented by Chris Wadsworth where an expression is

represented as a directed graph (usually drawn as an

inverted tree). Each node represents a function call and its

subtrees represent the arguments to that function. Subtrees

are replaced by the expansion or value of the expression they

represent. This is repeated until the tree has been reduced

to a value with no more function calls (a normal form).

In contrast to string reduction, graph reduction has the

advantage that common subexpressions are represented as

pointers to a single instance of the expression which is only

reduced once. It is the most commonly used technique for

implementing lazy evaluation.