antlr4

Development/antlr4.md

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+# ANTLR4
+
+Read [Getting Started with ANTLR v4](https://github.com/antlr/antlr4/blob/master/doc/getting-started.md).
+
+Assume you use Archlinux.
+
+Install [antlr4](https://www.archlinux.org/packages/extra/any/antlr4/).
+
+Add to `~/.bashrc`, `~/.zshrc`, `~/.config/fish/config.fish`:
+
+```sh
+export CLASSPATH=".:/usr/share/java/antlr-complete.jar:$CLASSPATH"
+```
+
+Sample `Condition.g4`:
+
+```antlr4
+grammar Condition;
+
+ADD: '+';
+SUB: '-';
+MUL: '*';
+DIV: '/';
+MOD: '%';
+
+EQ: '==';
+NEQ: '!=';
+LT: '<';
+LTE: '<=';
+GT: '>';
+GTE: '>=';
+NOT: '!';
+
+AND: [Aa] [Nn] [Dd];
+OR: [Oo] [Rr];
+IN: [Ii] [Nn];
+NOTIN: [Nn] [Oo] [Tt] [Ii] [Nn];
+
+LEFT_PAREN: '(';
+RIGHT_PAREN: ')';
+LEFT_BRACKET: '[';
+RIGHT_BRACKET: ']';
+
+UNDERSCORE: '_';
+DOUBLE_QUOTE: '"';
+DOLLAR: '$';
+COMMA: ',';
+POINT: '.';
+
+WHITESPACE: [ \t\n\r]+ -> skip;
+
+fragment DIGIT: [0-9];
+fragment LETTER: [a-zA-Z];
+
+TRUE_LITERAL
+    : [Tt] [Rr] [Uu] [Ee]
+    ;
+FALSE_LITERAL
+    : [Ff] [Aa] [Ll] [Ss] [Ee]
+    ;
+FLOAT_LITERAL
+    : DIGIT+ (POINT DIGIT+)
+    ;
+INT_LITERAL
+    : DIGIT+
+    ;
+STRING_LITERAL
+    : DOUBLE_QUOTE (~['"\n])*? DOUBLE_QUOTE
+    ;
+
+VAR
+    : DOLLAR (LETTER | DIGIT | UNDERSCORE)+
+    ;
+
+start: expression EOF;
+
+expression
+    : LEFT_PAREN expression RIGHT_PAREN # Paren
+    | LEFT_BRACKET elements+=expression (COMMA elements+=expression)* RIGHT_BRACKET # Array
+    | TRUE_LITERAL # TrueLiteral
+    | FALSE_LITERAL # FalseLiteral
+    | FLOAT_LITERAL # FloatLiteral
+    | INT_LITERAL # IntLiteral
+    | STRING_LITERAL # StringLiteral
+    | VAR # Var
+    | operator=(NOT | ADD | SUB) expression # Unary
+    | expression operator=(MUL | DIV | MOD) expression # Binary
+    | expression operator=(ADD | SUB) expression # Binary
+    | expression operator=(EQ | NEQ | LT | LTE | GT | GTE | IN | NOTIN) expression # Binary
+    | expression operator=AND expression # Binary
+    | expression operator=OR expression # Binary
+    ;
+```