(Plus42) Cash Flow Analysis: NPV, IRR%, MIR%, FMR%

[Thomas Okken]

(02-09-2022 10:54 AM)Werner Wrote:  If I understood the rules correctly, it should use the direct solver for NPV and the iterative one for IRR%, but how can I tell?

Hmmm... that's something I haven't really dealt with yet. The numerical solver puts several items on the stack: the solution in X, the last approximation before the solution in Y, the final function value in Z, and the exit status in T. The direct solver only puts the solution in X, and nothing else, so there's no reliable way of distinguishing the two cases.

There are workarounds, like putting something like L(COUNT:G(COUNT)+1) in the equation, to see how often it is being called. Or use TRACE mode: if the function is being called repeatedly, the numerical solver is at work; if it runs only once and the equation source code isn't shown, the direct solver is at work, evaluating a transformed equation; and if it runs only once and the equation source code is shown, the direct solver is at work, running an un-transformed equation, which happens when solving for a variable that is already isolated in the original equation, e.g. solving for X in X=Y+Z.

(Or use NSTK mode, when you can tell which solver was used by how much stuff there is on the stack when the solver returns.)