A Functional Web Service A web service, or web interface for the state-saving interpreter may contain algorithms that may have functional parts, or reusable intermediate algorithmic parts. The web service makes APIs (algorithms) available online (ubiquitously). The state-saving interpreter is an interpreter that saves its recursive and variable states so that the retry feature in trace may return to previous states in the trace. An example of functional parts in the state-saving interpreter is function calls in functions in the algorithm. An example of functional parts in a web service is a web interface for the previous idea. Functionalism in a state-saving interpreter could save time in development in using the retry feature. The user uses retry to restart a trace, e.g. when exiting a predicate. The user could debug possible bugs relating to functionalism using trace, for example to increase to a scope level, to correct a function or an argument in a call with functionalism, with retry to summarise a flaw. Functionalism could simplify development of a web-service. For example, the user uses an intermediate element to compute or display a result on a web service.