Function jsonlogic_rs::js_op::parse_float_add

pub fn parse_float_add(vals: &Vec<&Value>) -> Result<f64, Error>

Add values, parsing to floats first.

The JSONLogic reference implementation uses the JS parseFloat operation on the parameters, which behaves quite differently from the normal JS numeric conversion with Number(val). While the latter uses the toPrimitive method on the base object Prototype, the former first converts any incoming value to a string, and then tries to parse it as a float. The upshot is that things that normally parse fine into numbers in JS, like bools and null, convert to NaN, because you can't make "false" into a number.

The JSONLogic reference implementation deals with any values that evaluate to NaN by returning null. We instead will return an error, the behavior for non-numeric inputs is not specified in the spec, and returning errors seems like a more reasonable course of action than returning null.