Method evaluate

src/xpath_functions.rs:349–390

eval function for IsNode errors happen for wrong number/kind of arg

(&self,
                        _context: &context::Evaluation<'_, 'd>,
                        args: Vec<Value<'d>>)

    // eval function for IsNode
    // errors happen for wrong number/kind of arg
    fn evaluate<'d>(&self,
                        _context: &context::Evaluation<'_, 'd>,
                        args: Vec<Value<'d>>)
                        -> Result<Value<'d>, Error>
    {

        let mut args = Args(args);
        args.exactly(2)?;
        let kind = args.pop_string()?;
        // FIX: there is some conflict problem with xpath errors and error-chain
        //                .chain_err(|e| format!("Second arg to is_leaf is not a string: {}", e.to_string()))?;
        match kind.as_str() {
            "simple" | "leaf" | "common_fraction" | "2D" | "modified" | "scripted" => (), 
            _ => return Err( Error::Other(format!("Unknown argument value '{}' for IsNode",  kind.as_str())) ),
        };

        let nodes = args.pop_nodeset()?;
        if nodes.size() == 0 {
            return Err(Error::Other("Missing argument for IsNode".to_string() ));
        };
        return Ok(
            Value::Boolean( 
                nodes.iter()
                    .all(|node|
                        if let Node::Element(e) = node {
                            match kind.as_str() {
                                "simple" => IsNode::is_simple(e),
                                "leaf"   => MATHML_LEAF_NODES.contains(name(&e)),
                                "2D" => IsNode::is_2D(&e),
                                "modified" => MATHML_MODIFIED_NODES.contains(name(&e)),
                                "scripted" => MATHML_SCRIPTED_NODES.contains(name(&e)),
                                "common_fraction" => IsNode::is_common_fraction(e, usize::MAX, usize::MAX), 
                                _        => true,       // can't happen due to check above
                            }    
                        } else {
                            // xpath is something besides an element, so no match
                            false
                        }
                    )
            )
        );
    }
}

struct ToOrdinal;