pub fn derived_shape(
model: &Model,
target: MeasureId,
name: &str,
formula: &Formula,
) -> Result<(ValueType, Vec<CategoryId>)>Expand description
The shape a new derived measure target named name takes from its
formula: its value type and its categories, as the engine computes them
(an OVER drops categories, @ITEM is text, DATE a date). A formula
that reads the measure itself (a PREV recurrence) is typed with a
provisional measure over the categories of the other measures it reads.