start of work to match cql2 against json

[bitner]

This PR adds a reduce and match function to Expr. Both functions take an optional json argument that will be used to get the values of any properties to compare against.

expr.reduce(json) will attempt to solve any operations. If there is no json, this will reduce the expression by evaluating any operations that use constants. If there is a json passed in, it will pull any properties from that json and turn them into constants before trying to reduce.

expr.matches(json) will attempt to reduce the expression and if that expression gets reduced to just a single Expr::Bool, it will return that value.

• Arithmetic Operators
• Comparison Operators for Number
• Comparison Operators for Boolean
• Comparison Operators for Text
• Spatial Operators
• Temporal Operators
• Testing Framework for Reduce
• Implement Array Operators
• Implement Like
• Implement In
• Implement Not
• Implement Between
• Implement Cast from BBox to geos geometry

[bitner]

So, trying to set this up so that the reduce function can actually be used for any CQL2 expression to collapse things that don't need to go through to the base data. So say you had a CQL2 query like foo = 2 +7, you could use reduce to convert that to foo = 9 . To do that, I'll need to make the json input an option, if it can look up a property in the json, it will replace it with the value in that json. The matches function just looks to see if running reduce has boiled the entire expression down into an Expr::Bool and if so returns that value, if it couldn't reduce it all the way it returns an error.

[kylebarron]

I don't really know CQL so I didn't look too closely at the body of reduce (yet)

[gadomski]

Should probably just return false if to_wkt fails, not unwrap