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 is one of Dinamica EGO's five calculator functors. Its abbreviated (shorthand) syntax is $. See Calculator functor shorthand in the EGO Script documentation for the verbose and abbreviated forms, and Calculate Functors — Complete Operator Documentation for the full expression language reference.
| Name | Type | Description |
|---|---|---|
| Expression | Image Expression Type | Algebraic or logical expression that evaluates to a single numeric result. Must be enclosed in square brackets [ ] in EGO Script. |
| Name | Type | Description | Default Value |
|---|---|---|---|
| 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 |
| Name | Type | Description |
|---|---|---|
| Result | Real Value Type | The computed scalar value. |
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:
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.
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 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 propagation rules and defensive patterns are covered in Null Value Handling in the Calculate Functors documentation.
CalculateValue