Function binary 

pub fn binary(op: BinOp, a: &Value, b: &Value) -> Value

A binary operator over two values: the left operand’s error first, then the right’s; arithmetic over the numbers each coerces to, & over their texts, a comparison in Excel’s order of kinds. Its arithmetic and its comparison of two numbers are [arithmetic] and [compares] over [compare_numbers], which an evaluation of many cells at once calls over its lanes of numbers (KERNEL.26), so that each rule is written once.