NULL;
help("nops");
restart;
X := 1, 2, 3, 4;
                        X := 1, 2, 3, 4
Y := 0, 1, 2;
                          Y := 0, 1, 2
Nx := nops([X]);
                            Nx := 4
Ny := nops([Y]);
                            Ny := 3
for i to Nx do lx[i] := mul((x-X[k])/(X[i]-X[k]), k = 1 .. i-1)*mul((x-X[k])/(X[i]-X[k]), k = i+1 .. Nx) end do;
for j to Ny do ly[j] := mul((y-Y[k])/(Y[j]-Y[k]), k = 1 .. j-1)*mul((y-Y[k])/(Y[j]-Y[k]), k = j+1 .. Ny) end do;
F := lx[3]*ly[1];
           /1     1\                           /  1      \
      F := |- x - -| (x - 2) (-x + 4) (-y + 1) |- - y + 1|
           \2     2/                           \  2      /
eval(F, {x = 1.5, y = 1.7});
                         0.03281250000

NULL;
restart;
X := 1, 2, 3, 4;
                        X := 1, 2, 3, 4
Y := 0, 1, 2;
                          Y := 0, 1, 2
Nx := nops([X]);
                            Nx := 4
Ny := nops([Y]);
                            Ny := 3
F := [[-3, 7, 5], [0, 6, 0], [2, 4, -4], [3, 6, 1]];
      F := [[-3, 7, 5], [0, 6, 0], [2, 4, -4], [3, 6, 1]]
punkty := NULL;
                           punkty :=
for i to Nx do for j to Ny do punkty := punkty, [X[i], Y[j], F[i, j]] end do end do;
F;
         [[-3, 7, 5], [0, 6, 0], [2, 4, -4], [3, 6, 1]]
licznik := 1;
                          licznik := 1
for i to Nx do for j to Ny do F[i, j] := punkty[licznik][3]; licznik := licznik+1 end do end do;
F;
         [[-3, 7, 5], [0, 6, 0], [2, 4, -4], [3, 6, 1]]
obszar := 1;
                          obszar := 1
with(LinearAlgebra);

for i to Nx-1 do for j to Ny-1 do Fi := Matrix([[1, X[i], Y[j], X[i]*Y[j]], [1, X[i], Y[j+1], X[i]*Y[j+1]], [1, X[i+1], Y[j], X[i+1]*Y[j]], [1, X[i+1], Y[j+1], X[i+1]*Y[j+1]]]); Ff := Vector([F[i, j], F[i, j+1], F[i+1, j], F[i+1, j+1]]); a := 1/Fi.Ff; funkcja || obszar := x*y*a[4]+x*a[2]+y*a[3]+a[1]; przedzial || obszar := X[i] <= x and x <= X[i+1] and Y[j] <= y and y <= Y[j+1]; obszar := obszar+1 end do end do;
Dane := NULL;
                            Dane :=
for i to obszar-1 do Dane := Dane, przedzial || i, funkcja || i end do;

wykr := piecewise(Dane);
wykr := PIECEWISE([-4 x y + 3 x + 14 y - 6,

  1 <= x and x <= 2 and 0 <= y and y <= 1], [

  -4 x y + 3 x + 2 y + 6, 1 <= x and x <= 2 and 1 <= y and y <= 2

  ], [-4 x y + 2 x + 14 y - 4,

  2 <= x and x <= 3 and 0 <= y and y <= 1],

  [-2 x y - 2 y + 12, 2 <= x and x <= 3 and 1 <= y and y <= 2],

  [x y + x - y - 1, 3 <= x and x <= 4 and 0 <= y and y <= 1],

  [3 x y - x - 17 y + 15, 3 <= x and x <= 4 and 1 <= y and y <= 2

  ], [-4 x y + 3 x + 14 y - 6,

  1 <= x and x <= 2 and 0 <= y and y <= 1], [

  -4 x y + 3 x + 2 y + 6, 1 <= x and x <= 2 and 1 <= y and y <= 2

  ], [-4 x y + 2 x + 14 y - 4,

  2 <= x and x <= 3 and 0 <= y and y <= 1],

  [-2 x y - 2 y + 12, 2 <= x and x <= 3 and 1 <= y and y <= 2],

  [x y + x - y - 1, 3 <= x and x <= 4 and 0 <= y and y <= 1],

  [3 x y - x - 17 y + 15, 3 <= x and x <= 4 and 1 <= y and y <= 2]

  )
eval(wykr, {x = 1.5, y = 1});
                              6.5
NULL;
restart;
N := 20;
                            N := 20
with(RandomTools);
XY := evalf(Generate(listlist(rational(range = 0 .. 1), N, 2)));
Fi := Matrix(N);
           FiAssignMatrix(%id = 18446744074636050430)
c := .7;
                            c := 0.7
for i to N do for j to N do Fi[i, j] := sqrt((XY[i][1]-XY[j][1])^2+(XY[i][2]-XY[j][2])^2+c^2) end do end do;
with(LinearAlgebra);
ConditionNumber(Fi);
                                      7
                        9.736052966 10
``;