Needed Computations Shortcutting Needed Steps

We define a compilation scheme for a constructor-based strongly-sequential graph rewriting system which shortcuts some needed steps. The object code, what the compiler produces on input the rewriting system, is another constructor-based graph rewriting system that is normalizing for the original system when using an innermost strategy. Hence, the object code can be easily implemented by eager functions in a variety of programming languages. We then modify our object code in a way that avoids totally or partially the construction of the contracta of some needed steps of a computation. When computing normal forms in this way, both memory consumption and execution time are reduced compared to ordinary rewriting computations in the original system.