How to place unicode characters in my Antlr grammar?

Question

I am trying to build a grammar with the following:

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

But Antlr refuses to load the grammar.

Answer 1

Use a Java expression representing a Unicode character:

• 'π' = '\ u03C0'
• '∞' = '\ u221E'

This will work until '\ uFFFF'; Java does not support five-digit Unicode.