Precedence David A. Wheeler 18 Sep 2012 03:24 UTC

As promised, here's a precedence thread.

I think precedence is overrated for an infix notation in Scheme.  In real code, more than two-thirds of actual examples didn't even mix operators, and thus by definition had no need for precedence.  In the rest, every different operator adds only two new characters, { and }, which would often be used anyway for clarity.  So while precedence support is *common* elsewhere, actual code use doesn't give much evidence for the utility of precedence in Scheme.  Expressions where it merely *might* be useful are probably less than 10% of all cases, given the sample set of actual code we have (posted earlier).

That said, it *would* be possible to add support for precedence to curly-infix.  Such approaches are documented in the current SRFI draft, and code to do it is trivial.

So, is adding precedence critically important to gain widespread implementation and use of curly-infix?  Would adding precedence harm its adoption?  Would it be a wash?  If you think precedence is critically necessary, what operators should be supported?  Are we just talking *, /, +, -  (I'll grant that everyone agrees on THEIR precedence and direction)?  More?  Why?  There are many options if we went down that road - what would be the principle to decide between them?  In particular: Would anyone use curly-infix *if* it had precedence, and *not* otherwise?

I am not committing to add precedence (obviously),  indeed, I'm rather skeptical on the grounds that the additional complexity doesn't seem justified.  But I'd be curious to hear people's thoughts.

--- David A. Wheeler