GitHub user okram opened a pull request:
https://github.com/apache/tinkerpop/pull/729
TINKERPOP-1632: Create a set of default functions
https://issues.apache.org/jira/browse/TINKERPOP-1632
This is an implementation of lambda-less math capabilities in Gremlin
leveraging the String-based calculator model proposed by @twilmes. This model
deviates from Gremlin's standard function composition and nesting model to
provide a easy to read "math processor" that leverages Gremlin scopes for data
access (e.g. path data, map keys, and side-effects). The feature is
encapsulated in `MathStep` which implements `PathProcessor` and `Scoping`.
Furthermore, `by()`-modulation is supported. `by()`-modulators are applied in
the order in which the variable is first used in the equation. Thus:
```
g.V().as("a").out("knows").by("b").
math("b + a").
by(out().count()).
by("age")
```
In the above: `a` -> `age` and `b` -> `out().count()`. More complex
examples are provided below:
```
gremlin> g = TinkerFactory.createModern().traversal()
==>graphtraversalsource[tinkergraph[vertices:6 edges:6], standard]
gremlin> g.V().as('a').out('knows').as('b').math('a + b').by('age')
==>56.0
==>61.0
gremlin> g.V().as('a').out('created').as('b').
......1> math('b + a').
......2> by(both().count().math('_ + 100')).
......3> by('age')
==>132.0
==>133.0
==>135.0
==>138.0
gremlin> g.withSideEffect('x',10).V().values('age').math('_ / x')
==>2.9
==>2.7
==>3.2
==>3.5
gremlin>
g.withSack(1).V(1).repeat(sack(sum).by(constant(1))).times(10).emit().sack().math('sin
_')
==>0.9092974268256817
==>0.1411200080598672
==>-0.7568024953079282
==>-0.9589242746631385
==>-0.27941549819892586
==>0.6569865987187891
==>0.9893582466233818
==>0.4121184852417566
==>-0.5440211108893698
==>-0.9999902065507035
```
You can merge this pull request into a Git repository by running:
$ git pull https://github.com/apache/tinkerpop TINKERPOP-1632
Alternatively you can review and apply these changes as the patch at:
https://github.com/apache/tinkerpop/pull/729.patch
To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:
This closes #729
----
commit 6f1a1f7028f285c6e45b7e7596320710b91114c5
Author: Marko A. Rodriguez <[email protected]>
Date: 2017-10-03T23:37:10Z
first non-tested implementation of math()-step. It uses the @twilmes model
which parses a String representation of the expression.
commit 624a8d706e150cc15dc2412d66d3ac9a61b90682
Author: Marko A. Rodriguez <[email protected]>
Date: 2017-10-04T16:27:48Z
I wrote a small parser that is able to extract variables from an exp4j
equation. So far, it is pretty durable. This is a much cleaner way of
determining variables than via label, side-effect, and map analysis. However,
this means that the by()-modulations are with respects to the order in which
the variables are contained in the equation.
commit c36493b6d66406b0d6b50e6c292e6d43216b4c4c
Author: Marko A. Rodriguez <[email protected]>
Date: 2017-10-04T16:42:06Z
added MathTest to test math() using step labels, side-effects, and implicit
current -- and with various uses of by()-modulation. This is a really cool step.
commit dfddccaaa85898e046e6b7a5bd81da3d94777d7d
Author: Marko A. Rodriguez <[email protected]>
Date: 2017-10-04T17:01:53Z
added MathStepTest to test hashCode() and the custom variable finder. Found
a couple of problems in my parser and I fixed them. Forgot to make MathStep a
PathProcessor so that OLAP is smart about data access. Both OLTP and OLAP tests
pass.
commit 7217823c3ea73f2d32ffa975e417dcd49d40cbdd
Author: Marko A. Rodriguez <[email protected]>
Date: 2017-10-04T17:30:55Z
added math()-step to the reference docs and updated CHANGELOG and upgrade
docs.
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