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Programming Paradigms
Evaluation Order and Infinite Lists
Arbitrary evaluation order - with some limits

In a functional program an expression is evaluated with the purpose of producing a value

An expression is composed of subexpressions

An illustration of an expression with subexpressions. In this context we will assume that and is defined as a function. In Scheme, and is not definede as a function, because of the short circuit evaluation rule. If and is short circuited the evaluation order of the surrounding expression is constrained.

  • Subexpressions can be evaluated in an arbitrary order provided that

    • no errors occur in subexpressions

    • the evaluation of all subexpressions terminate

  • It is possible to evaluate subexpressions in parallel