Euler is a programming language created by Niklaus Wirth and Helmut Weber, conceived as an extension and generalization of ALGOL 60.
[1][2][3] The designers' goals were to create a language that is: Available sources indicate that Euler was operational by 1965.
Euler employs a general data type concept.
In Euler, arrays, procedures, and switches are not quantities which are declared and named by identifiers: in contrast to ALGOL, they are not quantities on the same level as variables.
If the elements are lists themselves, then a general tree structure is obtained.