Hi Jens Axel, Thanks for replying and explaining. Can you discriminate between a+b and |a+b| or a|+|b? I don't see how without using a language with it's own key-binding for |. I prefer my infix to be usable without forcing the user to go into a specific language. For the moment I use spaces. As ugly that I probably are not going to use my own infix :) Allowing spaces to be omitted restricts the names of variables too much deviating from Racket, imho. As I wrote before, I am just playing with a parser without explicit use of a push down automaton. So far my experience is that this is very well possible, in fact much easier. Thanks again, Jos
_____ From: jensaxelsoega...@gmail.com [mailto:jensaxelsoega...@gmail.com] On Behalf Of Jens Axel Søgaard Sent: viernes, 24 de abril de 2015 14:50 To: Jos Koot Cc: racket-users@googlegroups.com Subject: Re: infix notation embedded in Racket 2015-04-23 18:51 GMT+02:00 Jos Koot <jos.k...@gmail.com>: Long ago I made various parsers (most of them in Fortran or assembler) for expressions with infix notation. I always used push-down automata with two or more stacks. Now I am playing with macros in Racket that allow infix notation embedded in Racket without explicitly using push-down automata. However, I encounter a contradiction in my desires as explained below. I have looked at 'Infix expressions for PLT Scheme' available in planet and made by Jens Axel Søgaard. In his approach a+b is evaluated as though written as (+ a b). However: #lang at-exp scheme (require (planet soegaard/infix)) (define a+b 4) (define a 1) (define b 2) @${a+b} ; evaluates to 3 A Racket variable can contain characters such as +, -, * etc. This makes @${a+b} confusing (not necessarily ambiguous, though, depending on syntax and semantics. The rule is that operators such as +,-, * behave as operators in infix expressions. My intention was to support identifiers with, say, - in them using bar notation as in |foo-bar| but I never got around to add them. If one want to allow the usual operators in identifiers without a quoting mechanism, then spaces are need to separate operators and identifiers - which may or may not fell annoying. /Jens Axel -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to racket-users+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
