stream-sift

A minimal high-performance specification-backed stateful object matching engine

Installation

Until this project is published do this:

npm install --save stream-sift

Overview

What

stream-sift is a document [1] pattern-matching library. If you have used mongoDB query search syntax, this will feel familiar. Also, because stream-sift works at the document level, it is suitable to build higher-level abstractions that compile down to a stream-sift schema (eg: a RQL-like library). However, direct document pattern-matching can be (or is the) correct API sometimes (eg: HTTP payloads, function argument pattern-matching, ...).

[1] "Document" in the NoSQL sense; JavaScript "objects", Ruby "hashes", Elm "records", etc.

How

stream-sift is divided into a "core" and "library". The core is an engine suitable for building arbitrary $functions on top of. Currently this project is "batteries included" meaning that a $function library is included, but is entirely modular and apart from core. In the future the $function library will be made its own project.

$fn API

$eq / $neq

Check for an exact match.

{ input: { percent: 10 } }

{ input: { percent: { $eq: 10 } } } // true
{ input: { percent: { $eq: 20 } } } // false

You should not have to use $eq directly because it is the default semantic:

{ input: { percent: 10 } // true
{ input: { percent: 20 } } // false

$gt / $gte / $lt / $lte

Check for numeric conditions.

{ input: { percent: 10 } }

{ input: { percent: { $gt: 9 } } } // true
{ input: { percent: { $gt: 10 } } } // false
{ input: { percent: { $gte: 9 } } } // true
{ input: { percent: { $gte: 10 } } } // true
{ input: { percent: { $lt: 9 } } } // false
{ input: { percent: { $lt: 10 } } } // false
{ input: { percent: { $lte: 9 } } } // false
{ input: { percent: { $lte: 10 } } } // true

$cross / $crossOrEqual

$c / $ce

Non-directional threshold functions. Check if a number crosses a given level.

{ input: { percent: 10 } },   { input: { percent: 50 } },   { input: { percent: 10 } }

{ input: { percent: { $cross: 50 } } } // false, false, false
{ input: { percent: { $cross: 40 } } } // false, true, true
{ input: { percent: { $crossOrEqual: 50 } } } // false, true, true

$crossGreaterThan / $crossGreaterThanOrEqual / $crossLessThan / $crossLessThanOrEqual

$cgt / $cgte / $clt / $clte

Directional threshold functions. Check if numbers rise/fall (respective to the function) past a given level.

{ input: { percent: 10 } },   { input: { percent: 70 } },   { input: { percent: 30 } }

{ input: { percent: { $crossGreaterThan: 69 } } } // false, true, false
{ input: { percent: { $crossGreaterThan: 70 } } } // false, false, false
{ input: { percent: { $crossGreaterThanOrEqual: 69 } } }  // false, true, false
{ input: { percent: { $crossGreaterThanOrEqual: 70 } } }  // false, true, false
{ input: { percent: { $crossLessThan: 30 } } } // false, false, false
{ input: { percent: { $crossLessThan: 31 } } } // false, false, true
{ input: { percent: { $crossLessThanOrEqual: 30 } } }  // false, false, true
{ input: { percent: { $crossLessThanOrEqual: 31 } } }  // false, false, true

$not

Negate the sub-expression.

{ input: { percent: 100, foo: 'bar' } }, { input: { percent: 100, foo: 'zed' } }, { input: { percent: 50, foo: 'zed' } }

{ input: { $not { percent: 100 } } } // false, false, true

$or / $nor / $xor / $and / $nand

Logical functions.

{ input: { percent: 100, foo: 'bar' } }, { input: { percent: 100, foo: 'zed' } }, { input: { percent: 50, foo: 'zed' } }

{ input: { $or [ { percent: 100 }, { foo: 'bar' } ] } } // true, true, false
{ input: { $nor [ { percent: 100 }, { foo: 'bar' } ] } } // false, false, true
{ input: { $xor [ { percent: 100 }, { foo: 'bar' } ] } } // false, true, false
{ input: { $and [ { percent: 100 }, { foo: 'bar' } ] } } // true, false, false
// $and is the default semantic; thus usually does not need to be used directly:
{ input: { percent: 100, foo: 'bar' } } // true, false, false
{ input: { $nand [ { percent: 100 }, { foo: 'bar' } ] } } // false, true, true

Roadmap

New $fns

• $in
• $nin
• $regex