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"Take" (Incremental Object)

IncrementalObject["Take"] [{e1,e2,…},n]

creates an object that incrementally returns at most n values.

IncrementalObject["Take"] [inc,n]

creates an object that incrementally returns at most n values from the incremental object or incremental function inc.

Details

  • A "Take" incremental object is useful to limit the number of results that come from an incremental object.
  • The expression used as a source can be an object with any head, not necessarily List.
  • The expression inc can be an expression with head IncrementalObject.
  • The expression inc can be an object created by compiled code that uses IncrementalFunction.
  • The following functions are also supported:
  • dsi===dsjTrue, if dsi equals dsj
    FullForm[ds]full form of ds
    InputForm[ds]input form of ds

Examples

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Basic Examples  (1)

Create a new "Take" incremental object:

Wolfram Language code: obj = IncrementalObject["Take"][{1, 2, 3, 4, 5}, 2]

The first value:

Wolfram Language code: NextValue[obj]

The next value:

Wolfram Language code: NextValue[obj]

There are no more values, and a failure object is returned:

Wolfram Language code: NextValue[obj]

Scope  (4)

The expression argument does not have to be a list, just any compound expression:

Wolfram Language code: obj = IncrementalObject["Take"][f[a[], a[1]], 2];

The first value:

Wolfram Language code: NextValue[obj]

The next value:

Wolfram Language code: NextValue[obj]

The limit has been reached, and a failure object is returned:

Wolfram Language code: NextValue[obj]

An incremental object can be used in Table:

Wolfram Language code: obj = IncrementalObject["Take"][Range[10], 3]; Table[e, {e, obj}]

An incremental object can be used in Do:

Wolfram Language code: obj = IncrementalObject["Take"][Range[10], 3]; Do[Echo[e], {e, obj}]

"Take" incremental objects can use an IncrementalObject as a source:

Wolfram Language code: iobj = IncrementalObject["Range"][10];

Create an incremental object using the incremental object as a source:

Wolfram Language code: obj = IncrementalObject["Take"][iobj, 3]

A list of all the values in the incremental object:

Wolfram Language code: Table[e, {e, obj}]

"Take" incremental objects can use an IncrementalFunction as a source:

Wolfram Language code: ifun = FunctionCompile[IncrementalFunction[Function[{}, Do[IncrementalYield[i], {i, Infinity}]]]][];

Return the first value:

Wolfram Language code: NextValue[ifun]

Create an incremental object using the incremental function as a source:

Wolfram Language code: obj = IncrementalObject["Take"][ifun, 10]

Even though the underlying IncrementalFunction uses a limit of Infinity the number of values is limited by the "Take" incremental:

Wolfram Language code: Table[e, {e, obj}]

As expected there are 10 of them:

Wolfram Language code: Length[%]

Properties & Relations  (2)

InputForm  (1)

InputForm returns the serialized contents of a "Take" incremental object:

Wolfram Language code: InputForm[IncrementalObject["Take"][{1, 2, 3}, 3]]

This serialized form can be used to recreate the incremental object:

Wolfram Language code: IncrementalObject["Take", {"Source" :> IncrementalObject["Identity", {"Source" :> {1, 2, 3}, "Position" :> 1}], "Position" :> 1, "Start" :> 1, "End" :> 3, "Step" :> 1}]

SameQ  (1)

SameQ can be used to test whether two incremental objects contain the same sequence at the same position:

Wolfram Language code: obj1 = IncrementalObject["Take"][Range[1000], 100]; obj2 = IncrementalObject["Take"][Range[1000], 100]; obj1 === obj2

If one objects moves to the next value, the two objects are no longer the same:

Wolfram Language code: NextValue[obj1]; obj1 === obj2

Advancing the other object means that they are both now the same:

Wolfram Language code: NextValue[obj2]; obj1 === obj2