Feature Request: Mutual Recursion
Several classes of problem (eg, context-free grammar interpreters) are easily thought about and implemented by mutually recursive function calls,
For example, one of the Rosetta Code programming challenges is to implement the Hofstadter Female and Male Sequences (http://rosettacode.org/wiki/Mutual_recursion#PureBasic). As far as I'm aware, this isn't possible in Mathcad, but appears to be in a whole host of other languages including Matlab and Mathematica (two of Mathcad's major competitors). As the ultimate humilation, I wrote my first program in LibreOffice Basic to show that even a word processor can do mutual recursion whereas a mathematical application can't. Indeed, it seems as if even a pocket calculator can do it (see Ti-89 entry in the Rosetta listing).
Stuart
Rosetta Code Hofstadter Female and Male Sequence Challenge
Two functions are said to be mutually recursive if the first calls the second, and in turn the second calls the first.
Write two mutually recursive functions that compute members of the Hofstadter Female and Male sequences defined as:
F(0) = 1 ; M(0)=0
F(n) = n - M(F(n-1)), n > 0
M(n) = n - F(M(n-1)), n > 0
n = 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
F(n) = 1 1 2 2 3 3 4 5 5 6 6 7 8 8 9 9 10 11 11 12 13
M(n) = 0 0 1 2 2 3 4 4 5 6 6 7 7 8 9 9 10 11 11 12 12
LibreOffice Basic Function Definitions:
Function F(n as long) as long
If n = 0 Then
F = 1
ElseIf n > 0 Then
F = n - M(F(n - 1))
EndIf
End Function
Function M(n)
If n = 0 Then
M = 0
ElseIf n > 0 Then
M = n - F(M(n - 1))
EndIf
End Function
