#zerkel An adzerk-based query-ish language.

###Language Zerkel provides primitive integer and string literals, identifiers, sets, and a selection of boolean operators:

| operator/type | comment | examples | |---------------|---------|----------| | integers | syntax | 42, -7 | | strings | syntax | "foo", "C:\\\\Windows\\System32", "^(foo|bar)\s+" | | variables | syntax | count, _foo_bar, $location.postalCode | | . | property accessor | $location.postalCode, foo.bar.baz | | [, ] | set construction | [42, "foo"] | | (, ) | expression grouping | x < 100 AND (y < 50 OR z < 10) | | = | | foo = 42 | | <> | not equal | foo <> "bar" | | =~ | regex match | foo =~ "^(some|regular|expression).*$" | | !~ | not regex match | foo !~ "^(some|regular|expression).*$" | | > | | foo > 42 | | < | | foo < 42 | | >= | | foo >= 42 | | <= | | foo <= 42 | | AND | | foo = 42 AND bar < 100 | | OR | | foo = 42 OR bar < 100 | | NOT | | NOT (bar =~ "^foo") | | LIKE | wildcard match | foo LIKE "ba*" | | CONTAINS | set membership / substring | ["foo", "bar"] CONTAINS "foo", "foobar" CONTAINS "foo" |

Thus, queries may be written like:

count > 43 and (user = "bob" or user = "alice")
keywords contains "awesome"

All operators are available in upper and lowercase forms.

###Demo

Check out the live Zerkel scratchpad demo app and try some zerkel queries in your browser.

###Usage Queries can executed in coffeescript/javascript using the zerkel module, like so:

zerkel = require 'zerkel'

query = 'count > 43 and (user = "bob" or user = "alice")'
matchFn = zerkel.compile query
matchFn {count: 50, user: 'bob'} # true
matchFn {count: 12, user: 'alice'} # false
matchFn {count: 50, user: 'George Michael'} # terribly, unfortunately, false

You can also access properties on passed in objects, like so:

zerkel = require 'zerkel'

query = 'user.location = "open field west of a white house"'
matchFn = zerkel.compile query
matchFn {user: {name: 'bob', location: 'open field west of a white house'}} # true
matchFn {user: {name: 'alice', location: 'middle earth'}} # false

###Gzip Set the parser.MIN_GZIP_SIZE to a number, and if the length of the compiled JavaScript is greater than that it will be gzipped and base64 encoded, with GZ: prepended. The zerkel#makePredicate function will unzip automatically as necessary.

parser = require 'zerkel-parser'

parser.MIN_GZIP_SIZE = 50
parser.parse 'foo = 42'              # _helpers['getIn'](_env, 'foo')==42'
parser.parse '[42, 43] contains foo' # GZ:H4sIAAAAAAAAA9OINjHSMTGOVVODMvQy81JSK/zTNOIzUnMKUouKo9XTU0s889RjNeJT88p0FNTT8vPVNTUV7GwVDDQBm8CsuD8AAAA=

###Status

###License Apache 2.0