// Treerack syntax (self)

// whitespace handling:
wschar:alias        = [ \t\n\b\f\r\v];
wsc:ws              = wschar | comment;
ws-no-nl:alias:nows = [ \t\b\f\r\v]; // whitespace without newline

// comments:
block-comment:alias:nows   = "/*" ("*" [^/] | [^*])* "*/";
line-comment:alias:nows    = "//" [^\n]*;
comment-segment:alias:nows = line-comment | block-comment;
comment:nows               = comment-segment (ws-no-nl* "\n"? ws-no-nl* comment-segment)*;

// characters:
any-char        = "."; // equivalent to [^]
class-not       = "^";
class-char:nows = [^\\\[\]\^\-] | "\\" .; // caution: newline is accepted
char-range:nows = class-char "-" class-char; // foo
char-class:nows = "[" class-not? (class-char | char-range)* "]";

// strings (char sequence):
sequence-char:nows = [^\\"] | "\\" .; // caution: newline is accepted
char-sequence:nows = "\"" sequence-char* "\"";

// terminal parsers cannot be composed of other parsers:
terminal:alias = any-char | char-class | char-sequence;

// symbols can reference other parser definitions, or recursively the containing parser:
symbol:nows = [^\\ \n\t\b\f\r\v/.\[\]\"{}\^+*?|():=;]+;

// grouping allows, for example, use choices as sequence items:
group:alias      = "(" expression ")";
expression:alias = terminal | symbol | group | sequence | choice;

// sequences with ranges:
number:alias:nows = [0-9]+;
count             = number;
count-quantifier  = "{" count "}";
range-from        = number;
range-to          = number;
range-quantifier  = "{" range-from? "," range-to? "}";
one-or-more       = "+";
zero-or-more      = "*";
zero-or-one       = "?";
quantity:alias    = count-quantifier | range-quantifier | one-or-more | zero-or-more | zero-or-one;
item:nows         = (terminal | symbol | group) quantity?;
sequence          = item+;

// choices:
option:alias = terminal | symbol | group | sequence;
choice       = option ("|" option)+;

// flags control AST generation, whitespace handling and error propagation:
alias      = "alias";
ws         = "ws";
nows       = "nows";
kw         = "kw";
nokw       = "nokw";
failpass   = "failpass";
root       = "root";
flag:alias = alias | ws | nows | kw | nokw | failpass | root;

// a syntax document consists of definitions:
definition-name:alias:nows = symbol (":" flag)*;
definition                 = definition-name "=" expression;
definitions:alias          = definition (";"+ definition)*;
syntax:root                = ";"* definitions? ";"*;