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number_value [2011/07/31 19:20]
hermann created 		number_value [2026/08/28 03:29] (current)
hermann Sync from local documentation review
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-====== Number Value ====== ​+====== Number Value ======
  
 ===== Description ===== ===== Description =====
  
-This hook identifies a value by assigning a number to it.+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 ===== ===== Inputs =====
  
-^ Name ^ Type ^ Description ^ +^ Name  ^ Type  ^ Description ​ ^ 
-| Value  | [[Double ​Type|Double]]  | Any value.  | +| Value  | [[Real Value Type]] ​ | Value to identify.  | 
-| Value Number ​ | [[Positive ​Int Type|Positive Int]]  | Value number identifier.  |+| 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 ===== ===== Optional Inputs =====
 +
 +None.
  
 ===== Outputs ===== ===== Outputs =====
 +
 +None.
  
 ===== Group ===== ===== Group =====
  
-[[Functor List#Map Algebra Supplementary ​ | Map Algebra Supplementary ]]+[[Functor List#Map Algebra Supplementary | Map Algebra Supplementary]]
  
-===== Notes ===== +===== Notes =====
  
-A hook is usually used to enter a type of data into a container that performs some operation.+==== Purpose as a placeholder ====
  
-===== Internal Name ===== +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 NumberValue
 +
 +===== Usage examples =====
 +
 +[[Calculate Map#​Connecting data inputs|Connecting data inputs]] in the Calculate Map documentation — shows Number Value exposing a scalar as v1.