Euler (programming language)

Euler is a programming language created by Niklaus Wirth and Helmut Weber as an extension and generalization of ALGOL 60. Its designers wanted a language that was simpler yet more flexible than ALGOL 60, useful and processed with reasonable efficiency, and definable with rigorous formality. Sources indicate that it was operational by 1965. Where ALGOL treats arrays, procedures and switches as declared, named quantities, Euler places them on the level of constants, so that besides numbers and logical values it introduces references, labels, symbols, lists, procedures and an undefined value. Any constant can be assigned to a variable, because Euler uses dynamic typing rather than fixed variable types. A procedure can return a value of any type, lists can mix element types, and lists of labels give a switch while lists of lists give general tree structures. The language also provides general type-test and type-conversion operators.