Don Stewart wrote:
Which suggests that $ was already in the 1.0 report going to SIGPLAN. Perhaps Paul or Simon could shed light on it? Anyone have the 1.0 report lying around to check if it was in earlier?
As far as Haskell is concerned, the first "report"-ed occurrence of the $ operator was in the Haskell 1.2 report dated March 1992. I don't see any mention of the $ operator in either the 1.0 or the 1.1 reports (April 1990 and August 1991, respectively). The 1.0 report did define the following operator, which is a variant of $: let :: a -> (a -> b) -> b let x k = k x This was exported from the prelude, but its definition actually appeared in the PreludeIO section of the report, hinting at the main motivation for its introduction in support of continuation based I/O. (Monadic I/O didn't officially arrive until the 1.3 report in May 1996.) But the "let" operator was quickly promoted to a keyword in Haskell 1.1 with the introduction of let expressions, replacing the "where expressions" that Haskell 1.0 had provided for local definitions. With the move to 1.1, "where" became part of the syntax for definition right hand sides, able to scope across multiple guards and no longer part of the expression syntax. A little history can sometimes be fun. All the best, Mark