Re: [Flightgear-devel] Nasal advice...
Andy Ross wrote: More not-quite-FlightGear subject matter ahead. But I need advice: Nasal needs a character constant syntax. That is, the ability to write an ASCII charactrer as a numerical constant. In C/C++, you use single quotes to do this (e.g. the token 'A' is just a synonym for the integer value 65). (Brief background: I just added the ability to read and write individual bytes in a string with the [] operator, just like you can for elements of the vector. Thus the need for character constants to which to compare those bytes.) But Nasal can't do that, because it already uses single quotes for unescaped strings, something that will be really useful in the regular expression interface I am putting together. At first I was thinking using #'A' since # represents a number already in most cases, but then again; how about just using a new function? Erik ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
RE: [Flightgear-devel] Nasal advice...
Andy Ross wrote So anyway, which of the following are good/bad choices for a character constant syntax: `A` @A $A %A A @A $A %A A cA Anything but `A` - I'm bound to misread that in the future sometime. I favour a function. Regards, Vivian ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Nasal advice...
From: Andy Ross snip Perl and Python get away without having character constants at all. They do string indexing by making substrings at runtime. But substrings are garbage-collected, which makes them a little expensive. I don't want to thrash the heap just to iterate through a single string (the lack of the ability to do this really annoys me in perl). So basically, I can't just emulate C, perl or python here, I need to invent a new syntax. You could perhaps extend the w3 named entity syntax which uses as left delimiter and ; as right. So that A; would equal #65; But maybe the ; would be a parsing headache... Best regards, Jim ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
Re: [Flightgear-devel] Nasal advice...
Erik Hofman wrote: At first I was thinking using #'A' since # represents a number already in most cases, but then again; how about just using a new function? Just to be clear, there is a function to do this already: strc() returns the value of the Nth byte in a string. The index defaults to zero, so you can write strc(A) to get 65 right now. With the new syntax, you can even write A[0] to do the same. The problem (a minor one, admittedly) is that those are runtime operations that have to generate code. What I really want is the ability to just write the number 65 using some simple key combination involving the character A. :) I think I'm leaning towards back quotes, but I'm still not sure. Using backquotes has always meant something special, and character constants aren't very special... Andy ___ Flightgear-devel mailing list Flightgear-devel@flightgear.org http://mail.flightgear.org/mailman/listinfo/flightgear-devel 2f585eeea02e2c79d7b1d8c4963bae2d
