antlr4 all words except the operators - antlr4

Question

grammar TestGrammar;
AND : 'AND' ;
OR : 'OR'|',' ;
NOT : 'NOT' ;
LPAREN : '(' ;
RPAREN : ')' ;
DQUOTE : '"' ;
WORD : [a-z0-9._#+=]+(' '[a-z0-9._#+=]+)* ;
WS : [ \t\r\n]+ -> skip ;
quotedword : DQUOTE WORD DQUOTE;
expression
: LPAREN expression+ RPAREN
| expression (AND expression)+
| expression (OR​ expression)+
| expression (NOT​ expression)+
| NOT expression+
| quotedword
| WORD;
I've managed to implement the above grammar for antlr4.
I've got a long way to go but for now my question is,
how can I make WORD generic? Basically I want this [a-z0-9._#+=] to be anything except the operators (AND, OR, NOT, LPAREN, RPAREN, DQUOTE, SPACE).

Answer 1

The lexer will use the first rule that can match the given input. Only if that rule can't match it, it will try the next one.
Therefore you can make your WORD rule generic by using this grammar:
AND : 'AND' ;
OR : 'OR'|',' ;
NOT : 'NOT' ;
LPAREN : '(' ;
RPAREN : ')' ;
DQUOTE : '"' ;
WS : [ \t\r\n]+ -> skip ;
WORD: .+? ;
Make sure to use the non-greedy operator ? in this case becaue otherwise once invoked the WORD rule will consume all following input.
As WORD is specified last, input will only be tried to be consumed by it if all previous lexer rules (all that have been defined above in the source code) have failed.
EDIT: If you don't want your WORD rule to match any input then you just have to modify the rule I provided. But the essence of my answer is that in the lexer you don't have to worry about two rules potentially matching the same input as long as you got the order in the source code right.

Answer 2

Try something like this grammar:
grammar TestGrammar;
...
WORD : Letter+;
QUOTEDWORD : '"' (~["\\\r\n])* '"' // disallow quotes, backslashes and crlf in literals
WS : [ \t\r\n]+ -> skip ;
fragment Letter :
[a-zA-Z$_] // these are the "java letters" below 0x7F
| ~[\u0000-\u007F\uD800-\uDBFF] // covers all characters above 0x7F which are not a surrogate
| [\uD800-\uDBFF] [\uDC00-\uDFFF] // covers UTF-16 surrogate pairs encodings for U+10000 to U+10FFFF
;
expression:
...
| QUOTEDWORD
| WORD+;
Maybe you want to use escape sequences in QUOTEDWORD, then look in this example how to do this.
This grammar allows you:
to have quoted words interpreted as string literals (preserving all spaces within)
to have multiple words separated by whitespace (which is ignored)