====== Calculate Lookup Table Keys And Values ======

===== Description =====

Generates a new lookup table by evaluating **two separate expressions** once per row of a base lookup table — one expression for the output key and one for the output value. This allows complete transformation of a table's key-value structure, or construction of an entirely new lookup table row by row.

This functor is one of five in the [[calculate_functors|calculator family]]. Use it when you need to recompute both the keys and the values of a lookup table. If only the values need to be recomputed and the keys should be inherited from the base table, use [[Calculate Lookup Table Values]] instead.

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 =====

^ Name ^ Type ^ Description ^
| Key Column Expression | [[Image Expression Type]] | The formula evaluated for each row to produce the output key. Must be enclosed in square brackets ''[ ]'' in EGO Script. |
| Value Column Expression | [[Image Expression Type]] | The formula evaluated for each row to produce the output value. Must be enclosed in square brackets ''[ ]'' in EGO Script. |

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

^ Name ^ Type ^ Default ^ Description ^
| Key Column Name | [[Name Type]] | None | Name of the key column in the output lookup table. If omitted, the corresponding name from the base table is used. |
| Value Column Name | [[Name Type]] | None | Name of the value column in the output lookup table. If omitted, the corresponding name from the base table is used. |
| Base Lookup Table | [[Lookup Table Type]] | None | The lookup table whose row set drives iteration. When not provided, the [[Number Table]] hook with the lowest list index that is connected to a **lookup table** (not a regular table) is used as the row source (verbose form), or the first lookup table referenced by name in the expression (abbreviated form) — not a union of all connected tables. Prefer this port over a ''Number Table'' hook when the table is needed only to define the row set and is not referenced in the expression, to keep abbreviated syntax available. |

===== Output =====

^ Name ^ Type ^ Description ^
| Result | [[Lookup Table Type]] | A lookup table with both keys and values computed by the respective expressions. |

===== Group =====

[[Functor List#Table | Table]]

===== Notes =====

==== Connecting data inputs ====

Tables, lookup tables, and scalar values referenced in either expression must be connected to the functor's ports before writing the expressions, using **hook** functors:

  * Tables and lookup tables → [[Number Table]] → referenced in the expression as ''t1'', ''t2'', …, ''t100''
  * 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''. Both expressions share the same set of connected operands.

==== Row iteration context ====

Both expressions are evaluated once per row of the base lookup table. Two keywords reflect the current row inside each expression:

  * ''line'' — the **key** of the current row
  * ''column'' — the **value already associated with that key** in the base lookup table

If the key expression produces a key that already exists in the output table, the newly computed value replaces the existing one.

==== Available expression features ====

Identical to [[Calculate Lookup Table Values]]: arithmetic and logical operators, scalar references (''vX''), table and lookup table queries (''tX[...]'') in all single-key and multi-column forms, and the ''line'' and ''column'' row-context keywords are available. Image operators (''iX''), neighbourhood functions, neighbourhood indexing, and convolution are not available. See [[calculate_functors#the_expression_language|The Expression Language]] for the complete reference, or [[Image Expression Type]] for the navigable operator index.

==== 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.

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

''CalculateLookupTableKeysAndValues''