If You See What I Mean. Landin 1966. ISWIM is {purely functional}, a sugaring of {lambda-calculus}, and the ancestor of most modern applicative languages. An ISWIM program is a single expression qualified by ' where' clauses (auxiliary definitions including equations among variables), conditional expressions and function definitions. ISWIM was the first language to use lazy evaluation and introduced the {offside rule} for indentation. ["The Next 700 Programming Languages", P.J. Landin, CACM 9(3):157-166 (Mar 1966)].