[r6rs-discuss] [Formal] "#! /usr/bin/env" is not "portable." It's Unix-specific.

[Anton van Straaten]

Jens Axel Søgaard wrote:
> I am not sure, but I think some Scheme implementations use the
> syntax #!name  for other stuff (keywords, optionals? - I
> can't remember exactly)

A number of implementations use #!optional to indicate optionals.  Other 
such keywords that can be found in various Schemes include #!rest, 
#!eof, #!void, and #!null.

R5.91RS codifies this practice: see section 3, page 10, second last 
paragraph before 3.1, as well as 3.2.2.

Anton