Wil Macaulay wrote:
Yes, I do have a suggestion: if you really want to implement a 'generic parser', start by choosing a standard to implement. If you want to suggest changes to the standard, do so as an independent process. Otherwise you'll end up with a parser that only parses non-standard abc...
I've chosen the following approach: - first of all be compliant with 2.0 draft standard, - then include 1.6 standard as long as it does not harm the 2.0 compliancy - than include "non standard" (but commonly used and/or useful) syntax.
For example, the 2.0 standard includes the "-8" keyword to transpose an octave down, I've added the -15 and -22 keyword (that are avalaible in other notation packages) and also extended it to other clefs so that "treble-8" is recognized (as the 2.0 standard requires) but so does "baritone+15"!
There is one important thing to note here. ABCp is, at the present stage, a scanner, not a parser. This means that, in this case, ABCp reports to the host program that the user specified a clef with TWO octave transposition. It is entirely to the host program to decide if this is acceptable or not!
ABCp is an "enabler" for programmers that want to write software that accept ABC files as input. Using ABCp they can concentrate on the functions of their software instead of losing time to accomodate this or that ABC extension.
This concept is very crucial. Let me bore you a little bit with an example:. This is a 2.0 compliant Key:
K:Bb mix ^^c_d mezzosoprano transpose=+5 stafflines=3
while this is the same key
K:Bb Mix Db C## \ mezzo t5 s3
that makes use of some "extensions".
As far as the host program is concerned, the two keys above get reported exactly in the same way:
"[EMAIL PROTECTED] Sf [EMAIL PROTECTED] 053 @ "
(The string above is a "serialized" version of the binary representation of the parsed key field.)
The host program will use a function like abcKeyTonic() to get "Bb" and abcKeySemitoneTranspose() to get "5" regardless the way those information are actually represented in the abc file.
A function abcError() will report if something went wrong (for example if "K:Lmin" was encountered).
If the host program wants to deal with the string itself, it may well do so using the abcString() function that returns the Key string as it appears in the file.
I hope I've been clear enough. Please feel free to comment!
BTW. I still have to figure out a clean interface! The functions above (abcKeySemitoneTranspose for example) are so ugly that I'm a little be ashamed to publicly release them!
R:D
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