ISWIM

If You See What I Mean. Landin 1966. ISWIM is purelyfunctional, 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 offsiderule for indentation.

["The Next 700 Programming Languages", P.J. Landin, CACM

9(3):157-166 (Mar 1966)].