A simple query language.

crystal-query has not reached version 1.0.0; the interface and functionality may change at any time, and the documentation is incomplete.

crystal-query parses queries composed of lists of terms and logical operators (not, and, and or). A query conceptually defineds a predicate function over a set of objects.

A term consists of a field name, an operator, and a value.

A field name can be any word except the keywords not, and, and or.

The operators are :, >, >=, =, <=, and <.

A value can be any word except a keyword, or any string in double quotes ("a string"). Within a string, \ escapes the following character ("a double quote: \" and a backslash: \\").

Components of a term can be omitted.

Some valid fields: foo:bar, foo:"bar", foo>3, ="bar", foo, 3, "foo bar".

Terms can be modified and combined with not, and, and or. Expressions can be grouped with ().

foo>3 and not (foo<10 or bar:baz)

Terms can also be listed, which is equivalent to combining them with and.

"lorem" "ipsum" => "lorem" and "ipsum".