How do I put unicode characters in my Antlr grammar?

Question

I'm trying to build a grammar with the following:

NUMERIC: INTEGER | FLOAT | INFINITY | PI ... INFINITY: '∞' PI: 'π'

But Antlr refuses to load the grammar.

Answer 1

Use the Java expression representing the Unicode character:

• 'π' = '\u221E'
• '∞' = '\u03C0'

That will work up to '\uFFFF'; Java doesn't support five-digit Unicode.