alt Hacker News> Every language that has added sum types in the past twenty years has added, with its own syntax, what Ada's designers put in the original standard.
While true, that doesn't mean that other language's sum types originated in Ada. As [1] states,
> NPL and Hope are notable for being the first languages with call-by-pattern evaluation and algebraic data types
and a modern language like Haskell has origins in Hope (from 1980) through Miranda.
[1] https://en.wikipedia.org/wiki/Hope_(programming_language)
Replies
LLMCodeAuditor • today at 3:29 PM
[dead]
The origin of all sum types is in "Definition of new data types in ALGOL x", published by John McCarthy in October 1964, who introduced the keyword UNION for such types (he proposed "union" for sum types, "cartesian" for product types, and also operator overloading for custom types).
John McCarthy, the creator of LISP, had also many major contributions to ALGOL 60 and to its successors (e.g. he introduced recursive functions in ALGOL 60, which was a major difference between ALGOL 60 and most existing languages at that time, requiring the use of a stack for the local variables, while most previous languages used only statically-allocated variables).
The "union" of McCarthy and of the languages derived from his proposal is not the "union" of the C language, which has used the McCarthy keyword, but with the behavior of FORTRAN "EQUIVALENCE".
The concept of "union" as proposed by McCarthy was first implemented in the language ALGOL 68, then, as you mention, some functional languages, like Hope and Miranda, have used it extensively, with different syntactic variations.