MaplePrimes - answers and comments on Question, modulo, not only for integers

frac

Robert Israel — Fri, 01 Jan 2010 01:08:22 Z

frac(x/n) almost does it: the only problem is that frac(x) < 0 if x < 0. Instead try

> `&discretemod`:= proc(x::complexcons, n::realcons)
     if type(x, realcons) then x/n - floor(x/n)
     else Re(x)/n - floor(Re(x)/n) + I*(Im(x)/n - floor(Im(x)/n))
    end if
    end proc;

> (-3.2 - 7.6 * I) &discretemod 2;

.400000000+.200000000*I

thank you

Axel Vogt — Fri, 01 Jan 2010 01:21:00 Z

Thank you! That problem seems minor, I will care for it later:

  argument(exp(phi*I))=-argument(exp(-I*phi)); eval(%, phi=-Pi);
  map('t -> &discretemod(t, 2*Pi)', %);
  is(%);

                               Pi = -Pi
                              1/2 = 1/2
                                 true

method

jakubi — Fri, 01 Jan 2010 02:32:00 Z

I have posted a procedure for that here:

ar2:=y->y-2*Pi*ceil((y-Pi)/(2*Pi)):
argument(exp(phi*I))=-argument(exp(-I*phi)): 
eval(%, phi=-Pi);
map(ar2, %);
is(%);


                               Pi = -Pi

                               Pi = Pi

                                 true

b.t.w. another problem with evalc and argument

Axel Vogt — Sat, 02 Jan 2010 00:53:19 Z

Not sure whether I posted it already (Maple 12):

  A:=argument(exp(phi*I))+argument(1/exp(I*phi));
  B:=simplify(%);

  eval(B, phi=Pi);
                                 2 Pi
  evalc(B);
                                  0

  evalc(A);
  eval(%, phi=Pi);

                  phi + arctan(-sin(phi), cos(phi))

                                 2 Pi

method with 'ceil'

Axel Vogt — Fri, 01 Jan 2010 03:08:42 Z

Thank you, seems have had read your response at that time with the wrong eyeglasses :-(

problem with evalc

jakubi — Sat, 02 Jan 2010 01:42:37 Z

Probably, it would be better to report this problem.