tree 1a5168dbdfee27a74439fa1d662171ec431f612d
parent e9ffeb1074e374934093ac3a4eaf49f250291934
author Peter Kelly <peter@uxproductivity.com> 1438785442 +0700
committer Peter Kelly <peter@uxproductivity.com> 1438785825 +0700

Flat: Adjust syntax for grammar definitions

Change the syntax used for specifying grammar definitions as follows:

- Definitions contain a colon after the identifier instead of "<-", and
  must now end with a semicolon, e.g.:

    Grammar    : Spacing Definition+ EndOfFile;
    Definition : Identifier COLON Expression SEMI;

- Use | instead of / to delimit choices. The former is what is normally
  used for BNF-style grammar syntax and is likely to be more familiar to
  people. The original PEG grammar indicated that / was to denote
  ordered choice, but in Flat we'll just say that | is implicitly
  ordered choice.

- As a matter of style, use double quotes instead of single quotes for
  representing literals in the built-in grammar file, and when printing
  out grammars. This is not a change in the language, but just in the
  default representation.

The built-in grammar file, in experiments/flat/grammars, is now called
flat.flat instead of peg.peg, to reflect the fact that we're now moving
towards our own syntax, and adding new constructs that are not in pure
PEGs.