Function toNumber1_0

Converts a value to a number using XPath 1.0 rules (Appendix I.2).

XPath 1.0 numeric conversion rules:

• Number: as-is
• String: use fn:number() rules (parse as number, NaN if not parseable)
• Boolean: true = 1, false = 0
• Node-set: convert to string, then to number
• Empty sequence: NaN