Data.Greskell.GTraversal

This module defines GTraversal, greskell counterpart of GraphTraversal class object, and a DSL of composing graph traversal steps.

Types

GraphTraversal and others

newtype GTraversal c s e

GraphTraversal class object of TinkerPop. It takes data s from upstream and emits data e to downstream. Type c is called "walk type", a marker to describe the effect of the traversal.

GTraversal is NOT a Category. Because a GraphTraversal object keeps some context data, the starting (left-most) GraphTraversal object controls most of the behavior of entire composition of traversals and steps. This violates Category law.

Constructors

GTraversal

Fields

• unGTraversal :: Greskell (GraphTraversal c s e)

Instances

ToGTraversal GTraversal

Methods

toGTraversal :: WalkType c => GTraversal c s e -> GTraversal c s e

liftWalk :: (WalkType from, WalkType to, Lift from to) => GTraversal from s e -> GTraversal to s e

Bifunctor (GTraversal c)

Unsafely convert input and output types.

Methods

bimap :: (a -> b) -> (c -> d) -> GTraversal c a c -> GTraversal c b d

first :: (a -> b) -> GTraversal c a c -> GTraversal c b c

second :: (b -> c) -> GTraversal c a b -> GTraversal c a c

Functor (GTraversal c s)

Unsafely convert output type.

Methods

fmap :: (a -> b) -> GTraversal c s a -> GTraversal c s b

(<$) :: a -> GTraversal c s b -> GTraversal c s a

Show (GTraversal c s e)

Methods

showsPrec :: Int -> GTraversal c s e -> ShowS

show :: GTraversal c s e -> String

showList :: [GTraversal c s e] -> ShowS

ToGreskell (GTraversal c s e)

Unwrap GTraversal data constructor.

Associated Types

type GreskellReturn (GTraversal c s e) :: *

Methods

toGreskell :: GTraversal c s e -> Greskell (GreskellReturn (GTraversal c s e))

ProjectionLike (GTraversal Transform s e)

Associated Types

type ProjectionLikeStart (GTraversal Transform s e) :: *

type ProjectionLikeEnd (GTraversal Transform s e) :: *

ProjectionLike (GTraversal Filter s e)

Associated Types

type ProjectionLikeStart (GTraversal Filter s e) :: *

type ProjectionLikeEnd (GTraversal Filter s e) :: *

type GreskellReturn (GTraversal c s e)

type GreskellReturn (GTraversal c s e) = GraphTraversal c s e

type ProjectionLikeStart (GTraversal Transform s e)

type ProjectionLikeStart (GTraversal Transform s e) = s

type ProjectionLikeStart (GTraversal Filter s e)

type ProjectionLikeStart (GTraversal Filter s e) = s

type ProjectionLikeEnd (GTraversal Transform s e)

type ProjectionLikeEnd (GTraversal Transform s e) = e

type ProjectionLikeEnd (GTraversal Filter s e)

type ProjectionLikeEnd (GTraversal Filter s e) = e

data GraphTraversal c s e

Phantom type for GraphTraversal class. In greskell, we usually use GTraversal instead of Greskell GraphTraversal.

Instances

Bifunctor (GraphTraversal c)

Unsafely convert input and output types.

Methods

bimap :: (a -> b) -> (c -> d) -> GraphTraversal c a c -> GraphTraversal c b d

first :: (a -> b) -> GraphTraversal c a c -> GraphTraversal c b c

second :: (b -> c) -> GraphTraversal c a b -> GraphTraversal c a c

ProjectionLike (Greskell (GraphTraversal Transform s e))

Associated Types

type ProjectionLikeStart (Greskell (GraphTraversal Transform s e)) :: *

type ProjectionLikeEnd (Greskell (GraphTraversal Transform s e)) :: *

ProjectionLike (Greskell (GraphTraversal Filter s e))

Associated Types

type ProjectionLikeStart (Greskell (GraphTraversal Filter s e)) :: *

type ProjectionLikeEnd (Greskell (GraphTraversal Filter s e)) :: *

Functor (GraphTraversal c s)

Unsafely convert output type.

Methods

fmap :: (a -> b) -> GraphTraversal c s a -> GraphTraversal c s b

(<$) :: a -> GraphTraversal c s b -> GraphTraversal c s a

Show (GraphTraversal c s e)

Methods

showsPrec :: Int -> GraphTraversal c s e -> ShowS

show :: GraphTraversal c s e -> String

showList :: [GraphTraversal c s e] -> ShowS

type ProjectionLikeStart (Greskell (GraphTraversal Transform s e))

type ProjectionLikeStart (Greskell (GraphTraversal Transform s e)) = s

type ProjectionLikeStart (Greskell (GraphTraversal Filter s e))

type ProjectionLikeStart (Greskell (GraphTraversal Filter s e)) = s

type ProjectionLikeEnd (Greskell (GraphTraversal Transform s e))

type ProjectionLikeEnd (Greskell (GraphTraversal Transform s e)) = e

type ProjectionLikeEnd (Greskell (GraphTraversal Filter s e))

type ProjectionLikeEnd (Greskell (GraphTraversal Filter s e)) = e

class ToGTraversal g where

Types that can convert to GTraversal.

Minimal complete definition

toGTraversal, liftWalk

Methods

toGTraversal :: WalkType c => g c s e -> GTraversal c s e

liftWalk :: (WalkType from, WalkType to, Lift from to) => g from s e -> g to s e

Lift WalkType from to to. Use this for type matching.

Instances

ToGTraversal Walk

To convert a Walk to GTraversal, it calls its static method version on __ class.

Methods

toGTraversal :: WalkType c => Walk c s e -> GTraversal c s e

liftWalk :: (WalkType from, WalkType to, Lift from to) => Walk from s e -> Walk to s e

ToGTraversal GTraversal

Methods

toGTraversal :: WalkType c => GTraversal c s e -> GTraversal c s e

liftWalk :: (WalkType from, WalkType to, Lift from to) => GTraversal from s e -> GTraversal to s e

data Walk c s e

A chain of one or more Gremlin steps. Like GTraversal, type s is the input, type e is the output, and type c is a marker to describe the step.

Walk represents a chain of method calls such as .has(x).outE(). Because this is not a Gremlin (Groovy) expression, we use bare Walk, not Greskell Walk.

Walk is a Category. You can use functions from Control.Category to compose Walks. This is equivalent to making a chain of method calls in Gremlin.

Walk is not an Eq, because it's difficult to define true equality between Gremlin method calls. If we define it naively, it might have conflict with Category law.

Instances

ToGTraversal Walk

To convert a Walk to GTraversal, it calls its static method version on __ class.

Methods

toGTraversal :: WalkType c => Walk c s e -> GTraversal c s e

liftWalk :: (WalkType from, WalkType to, Lift from to) => Walk from s e -> Walk to s e

Bifunctor (Walk c)

Unsafely convert input and output types.

Methods

bimap :: (a -> b) -> (c -> d) -> Walk c a c -> Walk c b d

first :: (a -> b) -> Walk c a c -> Walk c b c

second :: (b -> c) -> Walk c a b -> Walk c a c

WalkType c => Category * (Walk c)

id is gIdentity.

Methods

id :: cat a a

(.) :: cat b c -> cat a b -> cat a c

Functor (Walk c s)

Unsafely convert output type

Methods

fmap :: (a -> b) -> Walk c s a -> Walk c s b

(<$) :: a -> Walk c s b -> Walk c s a

Show (Walk c s e)

Methods

showsPrec :: Int -> Walk c s e -> ShowS

show :: Walk c s e -> String

showList :: [Walk c s e] -> ShowS

WalkType c => Semigroup (Walk c s s)

Based on Category. <> is >>>.

Methods

(<>) :: Walk c s s -> Walk c s s -> Walk c s s

sconcat :: NonEmpty (Walk c s s) -> Walk c s s

stimes :: Integral b => b -> Walk c s s -> Walk c s s

WalkType c => Monoid (Walk c s s)

Based on Category and Semigroup. mempty is id.

Methods

mempty :: Walk c s s

mappend :: Walk c s s -> Walk c s s -> Walk c s s

mconcat :: [Walk c s s] -> Walk c s s

WalkType c => ToGreskell (Walk c s e)

The Walk is first converted to GTraversal, and it's converted to Greskell.

Associated Types

type GreskellReturn (Walk c s e) :: *

Methods

toGreskell :: Walk c s e -> Greskell (GreskellReturn (Walk c s e))

ProjectionLike (Walk Transform s e)

Associated Types

type ProjectionLikeStart (Walk Transform s e) :: *

type ProjectionLikeEnd (Walk Transform s e) :: *

ProjectionLike (Walk Filter s e)

Associated Types

type ProjectionLikeStart (Walk Filter s e) :: *

type ProjectionLikeEnd (Walk Filter s e) :: *

type GreskellReturn (Walk c s e)

type GreskellReturn (Walk c s e) = GraphTraversal c s e

type ProjectionLikeStart (Walk Transform s e)

type ProjectionLikeStart (Walk Transform s e) = s

type ProjectionLikeStart (Walk Filter s e)

type ProjectionLikeStart (Walk Filter s e) = s

type ProjectionLikeEnd (Walk Transform s e)

type ProjectionLikeEnd (Walk Transform s e) = e

type ProjectionLikeEnd (Walk Filter s e)

type ProjectionLikeEnd (Walk Filter s e) = e

data GraphTraversalSource

GraphTraversalSource class object of TinkerPop. It is a factory object of GraphTraversals.

Instances

Show GraphTraversalSource

Methods

showsPrec :: Int -> GraphTraversalSource -> ShowS

show :: GraphTraversalSource -> String

showList :: [GraphTraversalSource] -> ShowS

Walk types

class WalkType t

Class of phantom type markers to describe the effect of the walk/traversals.

Instances

WalkType SideEffect

WalkType Transform

WalkType Filter

data Filter

WalkType for filtering steps.

A filtering step is a step that does filtering only. It takes input and emits some of them without any modification, reordering, traversal actions, or side-effects. Filtering decision must be solely based on each element.

A Walk w is Filter type iff:

(gSideEffect w == gIdentity) AND (gFilter w == w)

If Walks w1 and w2 are Filter type, then

gAnd [w1, w2] == w1 >>> w2 == w2 >>> w1

Instances

WalkType Filter

WalkType p => Split Filter p

WalkType c => Lift Filter c

ProjectionLike (Greskell (GraphTraversal Filter s e))

Associated Types

type ProjectionLikeStart (Greskell (GraphTraversal Filter s e)) :: *

type ProjectionLikeEnd (Greskell (GraphTraversal Filter s e)) :: *

ProjectionLike (Walk Filter s e)

Associated Types

type ProjectionLikeStart (Walk Filter s e) :: *

type ProjectionLikeEnd (Walk Filter s e) :: *

ProjectionLike (GTraversal Filter s e)

Associated Types

type ProjectionLikeStart (GTraversal Filter s e) :: *

type ProjectionLikeEnd (GTraversal Filter s e) :: *

type ProjectionLikeStart (Greskell (GraphTraversal Filter s e))

type ProjectionLikeStart (Greskell (GraphTraversal Filter s e)) = s

type ProjectionLikeEnd (Greskell (GraphTraversal Filter s e))

type ProjectionLikeEnd (Greskell (GraphTraversal Filter s e)) = e

type ProjectionLikeStart (Walk Filter s e)

type ProjectionLikeStart (Walk Filter s e) = s

type ProjectionLikeStart (GTraversal Filter s e)

type ProjectionLikeStart (GTraversal Filter s e) = s

type ProjectionLikeEnd (Walk Filter s e)

type ProjectionLikeEnd (Walk Filter s e) = e

type ProjectionLikeEnd (GTraversal Filter s e)

type ProjectionLikeEnd (GTraversal Filter s e) = e

data Transform

WalkType for steps without any side-effects. This includes transformations, reordring, injections and graph traversal actions.

A Walk w is Transform type iff:

gSideEffect w == gIdentity

Obviously, every Filter type Walks are also Transform type.

Instances

WalkType Transform

WalkType p => Split Transform p

Transform effect in the child walk is rolled back in the parent walk.

Lift Transform SideEffect

Lift Transform Transform

ProjectionLike (Greskell (GraphTraversal Transform s e))

Associated Types

type ProjectionLikeStart (Greskell (GraphTraversal Transform s e)) :: *

type ProjectionLikeEnd (Greskell (GraphTraversal Transform s e)) :: *

ProjectionLike (Walk Transform s e)

Associated Types

type ProjectionLikeStart (Walk Transform s e) :: *

type ProjectionLikeEnd (Walk Transform s e) :: *

ProjectionLike (GTraversal Transform s e)

Associated Types

type ProjectionLikeStart (GTraversal Transform s e) :: *

type ProjectionLikeEnd (GTraversal Transform s e) :: *

type ProjectionLikeStart (Greskell (GraphTraversal Transform s e))

type ProjectionLikeStart (Greskell (GraphTraversal Transform s e)) = s

type ProjectionLikeEnd (Greskell (GraphTraversal Transform s e))

type ProjectionLikeEnd (Greskell (GraphTraversal Transform s e)) = e

type ProjectionLikeStart (Walk Transform s e)

type ProjectionLikeStart (Walk Transform s e) = s

type ProjectionLikeStart (GTraversal Transform s e)

type ProjectionLikeStart (GTraversal Transform s e) = s

type ProjectionLikeEnd (Walk Transform s e)

type ProjectionLikeEnd (Walk Transform s e) = e

type ProjectionLikeEnd (GTraversal Transform s e)

type ProjectionLikeEnd (GTraversal Transform s e) = e

data SideEffect

WalkType for steps that may have side-effects.

A side-effect here means manipulation of the "sideEffect" in Gremlin context (i.e. the stash of data kept in a Traversal object), as well as interaction with the world outside the Traversal object.

For example, the following steps (in Gremlin) all have side-effects.

.addE('label')
.aggregate('x')
.sideEffect(System.out.&println)
.map { some_variable += 1 }

Instances

WalkType SideEffect

Split SideEffect SideEffect

SideEffect in the child walk remains in the parent walk.

Lift SideEffect SideEffect

Lift Transform SideEffect

class Lift from to

Relation of WalkTypes where one includes the other. from can be lifted to to, because to is more powerful than from.

Instances

Lift SideEffect SideEffect

Lift Transform SideEffect

Lift Transform Transform

WalkType c => Lift Filter c

class Split c p

Relation of WalkTypes where the child walk c is split from the parent walk p.

When splitting, transformation effect done in the child walk is rolled back (canceled) in the parent walk.

Instances

Split SideEffect SideEffect

SideEffect in the child walk remains in the parent walk.

WalkType p => Split Transform p

Transform effect in the child walk is rolled back in the parent walk.

WalkType p => Split Filter p

GraphTraversalSource

source

Arguments

:: Text

variable name of GraphTraversalSource

-> Greskell GraphTraversalSource

Create GraphTraversalSource from a varible name in Gremlin

>>> toGremlin $ source "g"
"g"

sV

Arguments

:: Vertex v

=> [Greskell (ElementID v)]

vertex IDs

-> Greskell GraphTraversalSource

-> GTraversal Transform () v

.V() method on GraphTraversalSource.

sV' :: [Greskell Value] -> Greskell GraphTraversalSource -> GTraversal Transform () AVertex

Monomorphic version of sV.

>>> toGremlin (source "g" & sV' (map (value . Aeson.Number) [1,2,3]))
"g.V(1.0,2.0,3.0)"

sE

Arguments

:: Edge e

=> [Greskell (ElementID e)]

edge IDs

-> Greskell GraphTraversalSource

-> GTraversal Transform () e

.E() method on GraphTraversalSource.

sE' :: [Greskell Value] -> Greskell GraphTraversalSource -> GTraversal Transform () AEdge

Monomorphic version of sE.

>>> toGremlin (source "g" & sE' (map (value . Aeson.Number) [1]))
"g.E(1.0)"

GTraversal

(&.) :: GTraversal c a b -> Walk c b d -> GTraversal c a d infixl 1

Apply the Walk to the GTraversal. In Gremlin, this means calling a chain of methods on the Traversal object.

>>> toGremlin (source "g" & sV' [] &. gValues ["age"])
"g.V().values(\"age\")"

($.) :: Walk c b d -> GTraversal c a b -> GTraversal c a d infixr 0

Same as &. with arguments flipped.

>>> toGremlin (gValues ["age"] $. sV' [] $ source "g")
"g.V().values(\"age\")"

unsafeGTraversal :: Text -> GTraversal c s e

Unsafely create GTraversal from the given raw Gremlin script.

>>> toGremlin $ unsafeGTraversal "g.V().count()"
"g.V().count()"

Walk/Steps

Functions for TinkerPop graph traversal steps. For now greskell does not cover all graph traversal steps. If you want some steps added, just open an issue.

There may be multiple versions of Haskell functions for a single step. This is because Gremlin steps are too polymorphic for Haskell. greskell should be type-safe so that incorrect combination of steps is detected in compile time.

Low-level functions

unsafeWalk

Arguments

:: WalkType c

=> Text

step method name (e.g. "outE")

-> [Text]

step method arguments

-> Walk c s e

Unsafely create a Walk that represents a single method call on a GraphTraversal.

>>> toGremlin (source "g" & sV' [] &. unsafeWalk "valueMap" ["'foo'", "'bar'"])
"g.V().valueMap('foo','bar')"

modulateWith

Arguments

:: WalkType c

=> Walk c s e

the main Walk

-> [Walk c e e]

the modulating Walks

-> Walk c s e

Optionally modulate the main Walk with some modulating Walks.

>>> toGremlin (source "g" & sV' [] &. modulateWith (unsafeWalk "path" []) [unsafeWalk "by" ["'name'"], unsafeWalk "by" ["'age'"]])
"g.V().path().by('name').by('age')"

Filter steps

gIdentity :: WalkType c => Walk c s s

.identity step.

gIdentity' :: Walk Filter s s

Monomorphic version of gIdentity.

gFilter :: (ToGTraversal g, WalkType c, WalkType p, Split c p) => g c s e -> Walk p s s

.filter step that takes a traversal.

>>> toGremlin (source "g" & sV' [] &. gFilter (gOut' ["knows"]))
"g.V().filter(__.out(\"knows\"))"

Has steps

gHas1

Arguments

:: (WalkType c, Element s)

=> Key s v

property key

-> Walk c s s

.has step with one argument.

>>> toGremlin (source "g" & sV' [] &. gHas1 "age")
"g.V().has(\"age\")"

gHas1' :: Element s => Key s v -> Walk Filter s s

Monomorphic version of gHas1.

gHas2 :: (WalkType c, Element s) => Key s v -> Greskell v -> Walk c s s

.has step with two arguments.

>>> toGremlin (source "g" & sV' [] &. gHas2 "age" (31 :: Greskell Int))
"g.V().has(\"age\",31)"

gHas2' :: Element s => Key s v -> Greskell v -> Walk Filter s s

Monomorphic verson of gHas2.

gHas2P

Arguments

:: (WalkType c, Element s)

=> Key s v

property key

-> Greskell (P v)

predicate on the property value

-> Walk c s s

.has step with two arguments and P type.

>>> toGremlin (source "g" & sV' [] &. gHas2P "age" (pBetween (30 :: Greskell Int) 40))
"g.V().has(\"age\",P.between(30,40))"

gHas2P' :: Element s => Key s v -> Greskell (P v) -> Walk Filter s s

Monomorphic version of gHas2P.

gHasLabel :: (Element s, WalkType c) => Greskell Text -> Walk c s s

.hasLabel step.

>>> toGremlin (source "g" & sV' [] &. gHasLabel "person")
"g.V().hasLabel(\"person\")"

gHasLabel' :: Element s => Greskell Text -> Walk Filter s s

Monomorphic version of gHasLabel.

gHasLabelP

Arguments

:: (Element s, WalkType c)

=> Greskell (P Text)

predicate on Element label.

-> Walk c s s

.hasLabel step with P type. Supported since TinkerPop 3.2.7.

>>> toGremlin (source "g" & sV' [] &. gHasLabelP (pEq "person"))
"g.V().hasLabel(P.eq(\"person\"))"

gHasLabelP' :: Element s => Greskell (P Text) -> Walk Filter s s

Monomorphic version of gHasLabelP.

gHasId :: (Element s, WalkType c) => Greskell (ElementID s) -> Walk c s s

.hasId step.

>>> toGremlin (source "g" & sV' [] &. gHasId (value $ Aeson.Number 7))
"g.V().hasId(7.0)"

gHasId' :: Element s => Greskell (ElementID s) -> Walk Filter s s

Monomorphic version of gHasId.

gHasIdP :: (Element s, WalkType c) => Greskell (P (ElementID s)) -> Walk c s s

.hasId step with P type. Supported since TinkerPop 3.2.7.

>>> toGremlin (source "g" & sV' [] &. gHasIdP (pLte $ value $ Aeson.Number 100))
"g.V().hasId(P.lte(100.0))"

gHasIdP' :: Element s => Greskell (P (ElementID s)) -> Walk Filter s s

Monomorphic version of gHasIdP.

gHasKey :: (Element (p v), Property p, WalkType c) => Greskell Text -> Walk c (p v) (p v)

.hasKey step. The input type should be a VertexProperty.

>>> toGremlin (source "g" & sV' [] &. gProperties [] &. gHasKey "age")
"g.V().properties().hasKey(\"age\")"

gHasKey' :: (Element (p v), Property p) => Greskell Text -> Walk Filter (p v) (p v)

Monomorphic version of gHasKey.

gHasKeyP

Arguments

:: (Element (p v), Property p, WalkType c)

=> Greskell (P Text)

predicate on the VertexProperty's key.

-> Walk c (p v) (p v)

.hasKey step with P type. Supported since TinkerPop 3.2.7.

gHasKeyP' :: (Element (p v), Property p) => Greskell (P Text) -> Walk Filter (p v) (p v)

Monomorphic version of gHasKeyP.

gHasValue :: (Element (p v), Property p, WalkType c) => Greskell v -> Walk c (p v) (p v)

.hasValue step. The input type should be a VertexProperty.

>>> toGremlin (source "g" & sV' [] &. gProperties ["age"] &. gHasValue (32 :: Greskell Int))
"g.V().properties(\"age\").hasValue(32)"

gHasValue' :: (Element (p v), Property p) => Greskell v -> Walk Filter (p v) (p v)

Monomorphic version of gHasValue.

gHasValueP

Arguments

:: (Element (p v), Property p, WalkType c)

=> Greskell (P v)

predicate on the VertexProperty's value

-> Walk c (p v) (p v)

.hasValue step with P type. Supported since TinkerPop 3.2.7.

>>> toGremlin (source "g" & sV' [] &. gProperties ["age"] &. gHasValueP (pBetween (30 :: Greskell Int) 40))
"g.V().properties(\"age\").hasValue(P.between(30,40))"

gHasValueP' :: (Element (p v), Property p) => Greskell (P v) -> Walk Filter (p v) (p v)

Monomorphic version of gHasValueP.

Logic steps

gAnd :: (ToGTraversal g, WalkType c, WalkType p, Split c p) => [g c s e] -> Walk p s s

.and step.

>>> toGremlin (source "g" & sV' [] &. gAnd [gOut' ["knows"], gHas1 "age"])
"g.V().and(__.out(\"knows\"),__.has(\"age\"))"

gOr :: (ToGTraversal g, WalkType c, WalkType p, Split c p) => [g c s e] -> Walk p s s

.or step.

>>> toGremlin (source "g" & sV' [] &. gOr [gOut' ["knows"], gHas1 "age"])
"g.V().or(__.out(\"knows\"),__.has(\"age\"))"

gNot :: (ToGTraversal g, WalkType c, WalkType p, Split c p) => g c s e -> Walk p s s

.not step.

>>> toGremlin (source "g" & sV' [] &. gNot (gOut' ["knows"]))
"g.V().not(__.out(\"knows\"))"

Sorting steps

gOrder

Arguments

:: [ByComparator s]

following .by steps.

-> Walk Transform s s

.order step.

>>> let key_age = ("age" :: Key AVertex Int)
>>> toGremlin (source "g" & sV' [] &. gOrder [gBy1 key_age])
"g.V().order().by(\"age\")"
>>> toGremlin (source "g" & sV' [] &. gOrder [gBy2 key_age oDecr, gBy1 tId])
"g.V().order().by(\"age\",Order.decr).by(T.id)"
>>> toGremlin (source "g" & sV' [] &. gOrder [gBy2 (gOut' ["knows"] >>> gCount) oIncr, gBy2 tId oIncr])
"g.V().order().by(__.out(\"knows\").count(),Order.incr).by(T.id,Order.incr)"

Paging steps

gRange

Arguments

:: Greskell Int

min

-> Greskell Int

max

-> Walk Transform s s

.range step. This step is not a Filter, because the filtering decision by this step is based on position of each element, not the element itself. This violates Filter law.

>>> toGremlin (source "g" & sV' [] &. gRange 0 100)
"g.V().range(0,100)"

Transformation steps

gFlatMap :: ToGTraversal g => g Transform s e -> Walk Transform s e

.flatMap step.

.flatMap step is a Transform step even if the child walk is Filter type. This is because .flatMap step always modifies the path of the Traverser.

>>> toGremlin (source "g" & sV' [] &. gFlatMap (gOut' ["knows"] >>> gOut' ["created"]))
"g.V().flatMap(__.out(\"knows\").out(\"created\"))"

Accessor steps

gValues

Arguments

:: Element s

=> [Key s e]

property keys

-> Walk Transform s e

.values step.

>>> toGremlin (source "g" & sV' [] &. gValues ["name", "age"])
"g.V().values(\"name\",\"age\")"

gProperties :: (Element s, Property p, ElementProperty s ~ p) => [Key s v] -> Walk Transform s (p v)

.properties step.

>>> toGremlin (source "g" & sV' [] &. gProperties ["age"])
"g.V().properties(\"age\")"

Summarizing steps

gFold :: Walk Transform a [a]

.fold step.

gCount :: Walk Transform a Int

.count step.

Graph traversal steps

gOut

Arguments

:: (Vertex v1, Vertex v2)

=> [Greskell Text]

edge labels

-> Walk Transform v1 v2

.out step

gOut' :: Vertex v => [Greskell Text] -> Walk Transform v AVertex

Monomorphic version of gOut.

>>> toGremlin (source "g" & sV' ["person"] &. gOut' ["knows"])
"g.V(\"person\").out(\"knows\")"

gOutE

Arguments

:: (Vertex v, Edge e)

=> [Greskell Text]

edge labels

-> Walk Transform v e

.outE step

gOutE' :: Vertex v => [Greskell Text] -> Walk Transform v AEdge

Monomorphic version of gOutE

gIn

Arguments

:: (Vertex v1, Vertex v2)

=> [Greskell Text]

edge labels

-> Walk Transform v1 v2

.in step

gIn' :: Vertex v => [Greskell Text] -> Walk Transform v AVertex

Monomorphic version of gIn.

gInE

Arguments

:: (Vertex v, Edge e)

=> [Greskell Text]

edge labels

-> Walk Transform v e

.inE step.

gInE'

Arguments

:: Vertex v

=> [Greskell Text]

edge labels

-> Walk Transform v AEdge

Monomorphic version of gInE.

Side-effect steps

gSideEffect :: (ToGTraversal g, WalkType c, WalkType p, Split c p) => g c s e -> Walk p s s

.sideEffect step that takes a traversal.

gSideEffect' :: (ToGTraversal g, WalkType c, Split c SideEffect) => g c s e -> Walk SideEffect s s

Monomorphic version of gSideEffect. The result walk is always SideEffect type.

>>> toGremlin (source "g" & sV' [] & liftWalk &. gHas2 "name" "marko" &. gSideEffect' (gAddV' "toshio"))
"g.V().has(\"name\",\"marko\").sideEffect(__.addV(\"toshio\"))"

Graph manipulation steps

gAddV :: Vertex v => Greskell Text -> Walk SideEffect a v

.addV step with a label.

gAddV' :: Greskell Text -> Walk SideEffect a AVertex

Monomorphic version of gAddV.

gDrop :: Element e => Walk SideEffect e e

.drop step on Element.

>>> toGremlin (source "g" & sV' [] &. gHas2 "name" "marko" & liftWalk &. gDrop)
"g.V().has(\"name\",\"marko\").drop()"

gDropP :: Property p => Walk SideEffect (p a) (p a)

.drop step on Property.

>>> toGremlin (source "g" & sE' [] &. gProperties ["weight"] & liftWalk &. gDropP)
"g.E().properties(\"weight\").drop()"

.by steps

.by steps are not Walk on their own because they are always used in conjunction with other steps like gOrder.

data ByProjection s e where

Projection from type s to type e used in .by step. You can also use gBy to construct ByProjection.

Constructors

ByProjection :: (ProjectionLike p, ToGreskell p) => p -> ByProjection (ProjectionLikeStart p) (ProjectionLikeEnd p)

Instances

IsString (ByProjection s e)

Projection by literal property key.

Methods

fromString :: String -> ByProjection s e

ProjectionLike (ByProjection s e)

Associated Types

type ProjectionLikeStart (ByProjection s e) :: *

type ProjectionLikeEnd (ByProjection s e) :: *

type ProjectionLikeStart (ByProjection s e)

type ProjectionLikeStart (ByProjection s e) = s

type ProjectionLikeEnd (ByProjection s e)

type ProjectionLikeEnd (ByProjection s e) = e

class ProjectionLike p

Data types that mean a projection from one type to another.

Associated Types

type ProjectionLikeStart p

The start type of the projection.

type ProjectionLikeEnd p

The end type of the projection.

Instances

ProjectionLike (Greskell (s -> e))

Associated Types

type ProjectionLikeStart (Greskell (s -> e)) :: *

type ProjectionLikeEnd (Greskell (s -> e)) :: *

ProjectionLike (Greskell (T s e))

Associated Types

type ProjectionLikeStart (Greskell (T s e)) :: *

type ProjectionLikeEnd (Greskell (T s e)) :: *

ProjectionLike (Greskell (GraphTraversal Transform s e))

Associated Types

type ProjectionLikeStart (Greskell (GraphTraversal Transform s e)) :: *

type ProjectionLikeEnd (Greskell (GraphTraversal Transform s e)) :: *

ProjectionLike (Greskell (GraphTraversal Filter s e))

Associated Types

type ProjectionLikeStart (Greskell (GraphTraversal Filter s e)) :: *

type ProjectionLikeEnd (Greskell (GraphTraversal Filter s e)) :: *

ProjectionLike (Key s e)

Associated Types

type ProjectionLikeStart (Key s e) :: *

type ProjectionLikeEnd (Key s e) :: *

ProjectionLike (ByProjection s e)

Associated Types

type ProjectionLikeStart (ByProjection s e) :: *

type ProjectionLikeEnd (ByProjection s e) :: *

ProjectionLike (Walk Transform s e)

Associated Types

type ProjectionLikeStart (Walk Transform s e) :: *

type ProjectionLikeEnd (Walk Transform s e) :: *

ProjectionLike (Walk Filter s e)

Associated Types

type ProjectionLikeStart (Walk Filter s e) :: *

type ProjectionLikeEnd (Walk Filter s e) :: *

ProjectionLike (GTraversal Transform s e)

Associated Types

type ProjectionLikeStart (GTraversal Transform s e) :: *

type ProjectionLikeEnd (GTraversal Transform s e) :: *

ProjectionLike (GTraversal Filter s e)

Associated Types

type ProjectionLikeStart (GTraversal Filter s e) :: *

type ProjectionLikeEnd (GTraversal Filter s e) :: *

data ByComparator s where

Comparison of type s used in .by step. You can also use gBy1 and gBy2 to construct ByComparator.

Constructors

ByComparatorProj :: ByProjection s e -> ByComparator s

Type s is projected to type e, and compared by the natural comparator of type e.

ByComparatorComp :: Comparator comp => Greskell comp -> ByComparator (CompareArg comp)

Type s is compared by the Comparator comp.

ByComparatorProjComp :: Comparator comp => ByProjection s (CompareArg comp) -> Greskell comp -> ByComparator s

Type s is projected to type CompareArg comp, and compared by the Comparator comp.

Instances

IsString (ByComparator s)

ByComparatorProj by literal property key.

Methods

fromString :: String -> ByComparator s

gBy :: (ProjectionLike p, ToGreskell p) => p -> ByProjection (ProjectionLikeStart p) (ProjectionLikeEnd p)

.by step with 1 argument, used for projection.

gBy1 :: (ProjectionLike p, ToGreskell p) => p -> ByComparator (ProjectionLikeStart p)

.by step with 1 argumernt, used for comparison.

gBy2 :: (ProjectionLike p, ToGreskell p, Comparator comp, ProjectionLikeEnd p ~ CompareArg comp) => p -> Greskell comp -> ByComparator (ProjectionLikeStart p)

.by step with 2 arguments, used for comparison.