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"Identity" (Incremental Object)

IncrementalObject["Identity"] [{e1,e2,…}]

creates an object that incrementally returns the values e1, e2, ….

IncrementalObject["Identity"][inc]

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

Details

  • An "Identity" incremental object is useful as a source of values that come from the elements of an expression.
  • 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 "Identity" incremental object:

Wolfram Language code: obj = IncrementalObject["Identity"][{a, b}]

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["Identity"][f[a[1], b[1]]]; NextValue[obj]

An incremental object can be used in Table:

Wolfram Language code: obj = IncrementalObject["Identity"][{a, b}]; Table[e, {e, obj}]

An incremental object can be used in Do:

Wolfram Language code: obj = IncrementalObject["Identity"][{a, b}]; Do[Echo[e], {e, obj}]

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

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

Return the first value:

Wolfram Language code: NextValue[inc]

Create an incremental object using this as a source:

Wolfram Language code: obj = IncrementalObject["Identity"][inc]

The next value:

Wolfram Language code: NextValue[obj]

This underlying IncrementalFunction uses a limit of Infinity so the Table will not return:

Wolfram Language code: TimeConstrained[Table[e, {e, obj}], 1]

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

Wolfram Language code: obj1 = IncrementalObject["Range"][3]; obj = IncrementalObject["Identity"][obj1]

Return the values:

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

In practice it is not very useful to use an "Identity" incremental object in this way.

Properties & Relations  (2)

InputForm  (1)

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

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

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

Wolfram Language code: IncrementalObject["Identity", {"Source" :> {1, 2, 3}, "Position" :> 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["Identity"][{a, b, c, d}]; obj2 = IncrementalObject["Identity"][{a, b, c, d}]; 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