====== Number Value ======

===== Description =====

This hook functor identifies a value by assigning a number to it, so that a container built to consume numbered values — most commonly one of the calculator functors, such as [[Calculate Map]] — can pick it out by that number. It performs no computation itself: the enclosing container inspects its Value and Value Number ports and registers the value under that number, making it available as v''N'' inside the container's expression.

===== Inputs =====

^ Name  ^ Type  ^ Description  ^
| Value  | [[Real Value Type]]  | Value to identify.  |
| Value Number  | [[Positive Integer Value Type]]  | Number by which the value will be known inside the container — for example, 1 makes it available as v1.  |

===== Optional Inputs =====

None.

===== Outputs =====

None.

===== Group =====

[[Functor List#Map Algebra Supplementary | Map Algebra Supplementary]]

===== Notes =====

==== Purpose as a placeholder ====

Number Value only stores the value and the number under which it should be registered. The container it is placed inside inspects those ports and performs the actual registration.

==== Valid containers ====

This functor must be placed directly inside one of the containers that consume numbered values — [[Calculate Map]], [[Calculate Categorical Map]], [[Calculate Lookup Table Values]], [[Calculate Value]], [[Create String]], [[Calculate R Expression]], [[Calculate Python Expression]], or [[Calculate Lookup Table Keys And Values]]. Placing it inside any other functor is not supported and will fail validation.

==== Referencing the value in an expression ====

Once registered, the value is available inside the container's expression as vN (for example, Value Number = 1 gives v1). This applies to the verbose syntax only. The separate abbreviated syntax eliminates hook functors like Number Value entirely, referencing each connected input directly by its port name instead — see [[EGO Script#Calculator functor shorthand|Calculator functor shorthand]].

==== Visual banner ====

Value Number is normally set to a fixed constant chosen by the model author; connecting it to another functor's output instead reports a warning, since the identifier is meant to stay fixed and readable.

Once Value Number is set, this functor's banner in the model diagram shows "#N"; once the value itself is known, it reads "Value #N is X" (for example, "Value #1 is 42"), making the variable easy to identify in the diagram.

===== Internal Name =====

NumberValue

===== Usage examples =====

[[Calculate Map#Connecting data inputs|Connecting data inputs]] in the Calculate Map documentation — shows Number Value exposing a scalar as v1.