factorExpr method
Unary operators +x, -x, ~x.
Implementation
Parser<ExpressionNode> factorExpr() => [
seq2(
[ref1(token, '+'), ref1(token, '-'), ref1(token, '~')].toChoiceParser(),
ref0(factorExpr),
).map2((op, expr) => UnaryOpNode(operator: op.value, operand: expr)),
ref0(powerExpr),
].toChoiceParser();