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calculate_value [2026/07/04 23:47]
hermann 		calculate_value [2026/08/28 03:14] (current)
hermann Sync from local documentation review
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 ===== Description ===== ===== Description =====
  
-Evaluates an expression ​**once** and returns a single ​**scalar value**. Unlike the map and lookup table calculators,​ there is no current cell, row, or spatial grid — the expression is evaluated in a purely scalar context.+Evaluates an algebraic or logical ​expression once and returns a single scalar value. Unlike the map and lookup table calculators,​ there is no current cell, row, or spatial grid: the expression is evaluated in a purely scalar context, drawing only on tables, lookup tables, and scalar values connected through hooks.
  
-This functor ​is one of five in the [[calculate_functors|calculator ​family]]. Use it to compute a single parameter — such as a global threshold, a weighted sum of scalar inputs, or a value derived from a table — that can then be passed as input to other functors. +This is one of Dinamica EGO'​s ​five calculator functors. ​Its abbreviated (shorthand) ​syntax ​is ''​$''​. See [[ego_script#​calculator_functor_shorthand|Calculator functor shorthand]] in the EGO Script documentation for the verbose and abbreviated forms, and [[Calculate Functors|Calculate Functors — Complete Operator Documentation]] for the full expression language reference.
- +
-The **abbreviated ​syntax** ​(also called **shorthand**) for this functor ​is ''​$''​. See [[ego_script#​calculator_functor_shorthand|Calculator functor shorthand]] in the EGO Script documentation for the full syntax of both the verbose and abbreviated forms, and [[calculate_functors|Calculate Functors — Complete Operator Documentation]] for the complete ​expression language reference.+
  
 ===== Inputs ===== ===== Inputs =====
  
-^ Name ^ Type ^ Description ^ +^ Name  ^ Type  ^ Description ​ ^ 
-| Expression | [[Image Expression Type]] | The algebraic ​or logical ​formula ​that evaluates to a single numeric result, written using the [[Image Expression Type|image expression editor]]. Must be enclosed in square brackets ''​[ ]''​ in EGO Script. |+| Expression ​ | [[Image Expression Type]] ​ | Algebraic ​or logical ​expression ​that evaluates to a single numeric result. Must be enclosed in square brackets ''​[ ]''​ in EGO Script. ​ |
  
 ===== Optional Inputs ===== ===== Optional Inputs =====
  
-^ Name ^ Type ^ Default ​^ Description ^ +^ Name  ^ Type  ^ Description ​ ^ Default Value  ​^ 
-| Default Value | [[Real Value Type]] ​| None | Value returned if the expression produces an algebraic error. When provided, ​acts as a catch-all fallback equivalent to wrapping the entire expression in the ''?''​ operator. |+| Default Value  | [[Real Value Type]] ​ | Value returned if evaluating ​the expression produces an algebraic error. When not provided, ​evaluation errors are propagated. This is an advanced port.  | .none  ​|
  
-===== Output ​=====+===== Outputs ​=====
  
-^ Name ^ Type ^ Description ^ +^ Name  ^ Type  ^ Description ​ ^ 
-| Result | [[Real Value Type]] | The computed scalar value. |+| Result ​ | [[Real Value Type]] ​ | The computed scalar value. ​ |
  
 ===== Group ===== ===== Group =====
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 ==== Connecting data inputs ==== ==== Connecting data inputs ====
  
-Tables, lookup tables, and scalar values referenced in the expression must be connected to the functor'​s ports before writing the expression, using **hook** functors:+Tables, lookup tables, and scalar values referenced in the expression must be connected to the functor'​s ports before writing the expression, using hook functors:
  
-  * Tables and lookup tables → [[Number Table]] → referenced in the expression as ''​t1''​, ''​t2''​, …, ''​t100''​ +  * Tables and lookup tables → [[Number Table]] → referenced in the expression as t1, t2, …, t100 
-  * Scalar values → [[Number Value]] → referenced as ''​v1''​, ''​v2''​, …, ''​v100''​+  * Scalar values → [[Number Value]] → referenced as v1, v2, …, v100
  
 Maps cannot be connected — there is no cell context in this functor. In the abbreviated syntax, tables are referenced as ''​%variableName''​ and values as ''​$variableName''​. Maps cannot be connected — there is no cell context in this functor. In the abbreviated syntax, tables are referenced as ''​%variableName''​ and values as ''​$variableName''​.
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 ==== Available expression features ==== ==== Available expression features ====
  
-Image operators (''​iX''​),​ the ''​line'' ​and ''​column'' ​spatial keywords, neighbourhood functions, neighbourhood indexing, and convolution are not available — there is no cell or row context. Available features are arithmetic and logical operators and lookup table queries (''​tX[...]''​) in all single-key and multi-column forms. See [[calculate_functors#the_expression_language|The Expression Language]] for the complete reference, or [[Image Expression Type]] for the navigable operator index.+Image operators (''​iX''​),​ the line and column spatial keywords, neighbourhood functions, neighbourhood indexing, and convolution are not available — there is no cell or row context. Available features are arithmetic and logical operators ​and table and lookup table queries (''​tX[...]''​) in all single-key and multi-column forms. See [[Calculate Functors#The Expression Language|The Expression Language]] for the complete reference, or [[Image Expression Type]] for the navigable operator index. 
 + 
 +All operations are performed using the precision defined by ImageExpression::​Value;​ the final result is then converted to a double-precision real. See [[Calculate Value 2]] for a variant that instead performs all operations using double precision throughout.
  
 ==== Null value handling ==== ==== Null value handling ====
  
-Null propagation rules and defensive patterns are covered in [[calculate_functors#null_value_handling|Null Value Handling]] in the Calculate Functors documentation.+Null propagation rules and defensive patterns are covered in [[Calculate Functors#Null Value Handling|Null Value Handling]] in the Calculate Functors documentation.
  
 ===== Internal Name ===== ===== Internal Name =====
  
-''​CalculateValue''​+CalculateValue
  
 ===== Usage examples ===== ===== Usage examples =====
  
-  * [[calculate_functors#calculatevalue_examples|CalculateValue practical examples]] in the Calculate Functors documentation+  * [[Calculate Functors#CalculateValue practical examples|CalculateValue practical examples]] in the Calculate Functors documentation
   * [[lesson_8|Lesson 8: Inserting and getting a specific value into a table]]   * [[lesson_8|Lesson 8: Inserting and getting a specific value into a table]]
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