1. But

Build a function or function_c concept from a FORMULE function with 1 or 2 variables. Real functions with real variables, complex functions with real variables, and sheets can be defined.

It is also possible to produce a new real or complex function, or a sheet, by interpolating another function of the same type (real, complex or a sheet).

The use of CALC_FONC_INTERP allows a tabulation of the formula prior to the calculation. Its use is recommended before any transient and/or non-linear analysis for performance reasons.

The operator is not reentering, he is producing a new function or a tablecloth.