Editing Euler (programming language)

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{{Infobox programming language
| name = Euler
| logo = 
| paradigms = [[Multi-paradigm programming language|Multi-paradigm]]: [[Procedural programming|procedural]], [[Imperative programming|imperative]], [[Structured programming|structured]]
| family = [[ALGOL]] [[Niklaus Wirth|Wirth]]
| designers = [[Niklaus Wirth]]<br />Helmut Weber
| developers = [[Stanford University]]<br />[[ETH Zurich]]
| released = {{Start date and age|1965}}
| latest release version =
| latest release date =
| typing = [[Dynamic typing|dynamic]]
| scope = [[Scope (computer science)|Lexical]]
| programming language = 
| platform = 
| operating system = 
| license = 
| file ext = 
| website = <!-- {{URL|www.example.com}} -->
| influenced by = [[ALGOL 60]]
| influenced = 
}}
'''Euler''' is a [[programming language]] created by [[Niklaus Wirth]] and Helmut Weber, conceived as an extension and generalization of [[ALGOL 60]].<ref>
{{Cite journal |last1=Wirth |first1=Niklaus |author-link=Niklaus Wirth |last2=Weber |first2=Helmut |date=1966 |title=Euler: a generalization of ALGOL, and its formal definition: Part I |journal=Communications of the ACM |volume=9 |issue=1 |pages=13–25}}</ref><ref>
{{Cite journal |last1=Wirth |first1=Niklaus |author-link=Niklaus Wirth |last2=Weber |first2=Helmut |date=1966 |title=Euler: a generalization of ALGOL, and its formal definition: Part II |journal=Communications of the ACM |volume=9 |issue=2 |pages=89–99}}</ref><ref>
{{Cite report |last=Christopher |first=Thomas W. |date=1997 |title=Euler: An Experiment in Language Definition |url=http://www.iit.edu/~tc/euler.pdf |publisher=Illinois Institute of Technology |archive-url=https://web.archive.org/web/20060901063907/http://www.iit.edu/~tc/euler.pdf |archive-date=1 September 2006 |url-status=dead}}</ref> The designers' goals were to create a language that is:
* Simpler, yet more flexible, than ALGOL 60
* Useful and processed with reasonable efficiency
* Definable with [[Formal methods|rigorous formality]]

Available sources indicate that Euler was operational by 1965.

==Overview==
Euler employs a general [[data type]] concept. In Euler, [[Array data type|arrays]], [[Subroutine|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 [[Variable (computer science)|variables]]. Rather, these quantities are on the level of numeric and boolean [[Constant (computer programming)|constants]]. Thus, besides the traditional numeric and logical constants, Euler introduces several added types:
* Reference
* [[Label (programming language)|Label]]
* [[Symbol (programming)|Symbol]]
* List (array)
* Procedure
* Undefined
All constants can be assigned to variables, which have the same form as in ALGOL, but for which no fixed types are specified: Euler uses [[dynamic typing]]. Further, a procedure can produce a value of ''any'' type when executed, and this type can vary ''from one call of the procedure to the next''.

Similarly, the elements of a list can have values of any type and these can differ from element to element within a list. So, when the list elements are labels, a switch is obtained. If the elements are procedures, a procedure list is obtained, which is unavailable in ALGOL 60. If the elements are lists themselves, then a general tree structure is obtained.

Euler provides general type-test and type-conversion operators.

== See also ==
* [[Wirth–Weber precedence relationship]]
* [[Simple precedence parser]]

== References ==
{{Reflist}}

== External links ==
* {{GitHub|pkimpel/retro-b5500/tree/master/source/EULER}} - EULER IV for the [[Burroughs Large Systems#B5000|Burroughs B5500]] from 1965
* {{GitHub|gtownsend/icon/tree/master/ipl/packs/euler}} - An implementation written in [[Icon (programming language)|Icon]] from 2000-2001

{{Wirth}}

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[[Category:Dynamically typed programming languages]]