What (who) is interpreter - definition

In computer science, an interpreter is a computer program that directly executes instructions written in a programming or scripting language, without requiring them previously to have been compiled into a machine language program. An interpreter generally uses one of the following strategies for program execution:

<theory> Geoff Burn defines evaluators E0, E1, E2 and E3 which when applied to an expression, reduce it to varying degrees. E0 does no evaluation, E1 it evaluates to {weak head normal form} (WHNF), E2 evaluates the structure of a list, i.e. it evaluates it either to NIL or evaluates it to a CONS and then applies E2 to the second argument of the CONS. E3 evaluates the structure of a list and evaluates each element of the list to WHNF. This concept can be extended to data structures other than lists and forms the basis of the {evaluation transformer} style of strictness analysis. (1994-12-12)