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ISWIM unimplemented computer programming language described in the article by {Peter J. Landin} cited below. Landin attempted to capture all known programming language concepts, including {assignment} and control operators such as {goto} and {coroutines}, within a single {lambda calculus} based framework. ISWIM is an {imperative language} with a functional core, consisting of {sugared} {lambda calculus} plus {mutable variables} and {assignment}. A powerful control mechanism, Landin's {J operator}, enables capture of the current {continuation} (the {call/cc} operator of {Scheme} is a simplified version). Being based on lambda calculus ISWIM had {higher order functions} and {lexically scoped} variables. The {operational semantics} of ISWIM are defined using Landin's {SECD machine} and use {call-by-value} ({eager evaluation}). To make ISWIM look more like mathematical notation, Landin replaced {ALGOL}'s semicolons and begin end blocks with the {off-side rule} and scoping based on indentation. An ISWIM program is a single {expression} qualified by "where" clauses (auxiliary definitions including equations among variables), conditional expressions and function definitions. With {CPL}, ISWIM was one of the first programming languages to use "where" clauses. New {data types} could be defined as a (possibly recursive) {sum of products} like the {algebraic data types} found in modern functional languages. ISWIM variables were probably {dynamically typed} but Landin may have planned some form of {type inference}. Concepts from ISWIM appear in Art Evan's {PAL} and John Reynold's {Gedanken}, Milner's {ML} and purely functional languages with lazy evaluation like {SASL}, {Miranda} and {Haskell}. [{"The Next 700 Programming Languages" (http://www.cs.utah.edu/~wilson/compilers/old/papers/p157-landin.pdf)}, P.J. Landin, CACM 9(3):157-166, Mar 1966]. (2007-03-20)
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