Backwards Context Approximation

Context analysis calculates which components of arguments to functions may be evaluated eagerly without introducing non-termination. An amount of evaluation recommended by context analysis is less than the amount of evaluation which will occur at run-time. We may similarly derive contexts which are greater than the amount of run-time evaluation and hence determine which components of an expression are never evaluated and may be disposed of. 1 Introduction One of the major inefficiencies of functional language implementations is due to non-strict evaluation --- arguments which are passed lazily are stored with the values of the current variables until they need to be evaluated. The structure which associates an expression with the values of current variables is called a suspension, and it is the creation of this suspension which is wasteful. If we were to evaluate the expression when it is passed as an argument (as happens in common procedural languages), we would not need to create a ..