Wronskian

[salvomic]

A little better version:

Code:


ChooseType()
BEGIN
LOCAL choice;
CHOOSE(choice,"Matrix or Wronskian","Fundamental Matrix","Wronskian");
RETURN choice;
END;

#cas
// Wronskian - input a [vector] of functions
// i.e. W(f,g)= fg'-f'g
wronskian(flist):=
BEGIN
local mat, s, j, k, d;
s:= size(flist);

IF (  (s < 2) OR (TYPE(flist) == 2) OR (TYPE(flist(1))==2) OR (TYPE(flist(2))==2) ) THEN return "Input a [vector] of functions";
ELSE
IF (instring(string(flist),"[")==0) THEN  MSGBOX("It would be better use [vector] in []"); END;
mat:= makemat(0, s, s);
mat[1]:= flist;
FOR j FROM 2 TO s DO // diff

FOR k FROM 1 TO s DO // items
d:=diff(mat[j-1,k],x);
mat[j, k]:= d;

END; // for k
END; // for j
IF EXPR(" wronskian.ChooseType()")=1 THEN
return mat;
ELSE
return det(mat);
END; // if

END; // 1st if

END;
#end

It is not so elegant (it's perhaps "folkloristic", but with

Code:


IF (instring(string(flist),"[")==0) THEN  MSGBOX("It would be better use [vector] in []"); END;

I control if a list has [ bracket, and if not the program accepts also input with {} or simple list a,b,c..., but with a MSGBOX with a warning... better than nothing