Random walk — Georg Nees, 1969

Reading of the prose · no original listing

ALGOL 60

'BEGIN' 'COMMENT' IRRWEG.,
OPEN(0,0).,
LEER(-130,-90)., LINE(130,-90).,
LINE(130,90)., LINE(-130,90)., LINE(-130,-90).,
X.=0., Y.=0., LEER(X,Y).,
'FOR' I.=1 'STEP' 1 'UNTIL' 2000 'DO'
'BEGIN'
   'IF' 2*(I/2) 'NOTEQUAL' I 'THEN'
      X.= Reflexion(X + K1)
   'ELSE'
      Y.= Reflexion(Y + K2).,
   LINE(X,Y)
'END'.,
CLOSE
'END' IRRWEG.,

C K1, K2: same generators as J,
C interval −10…+10. Seed K2 = first power
C minus 1, K1 = K2 − 52.
C Fig. 6: 64 … Fig. 10: 1024 … Fig. 12: 4096.

Figs. 6–12 · kernel from p. 125

JavaScript

const K1 = makeGenerator(p1 - 53, [4*p1, 2*p1, p1]);
const K2 = makeGenerator(p1 - 1,  [4*p1, 2*p1, p1]);
let x = 0, y = 0;
LEER(0, 0);
for (let I = 1; I <= 2000; I++) {
  const d = Math.round(I % 2 === 1 ? K1(-10, 10) : K2(-10, 10));
  if (I % 2 === 1) x = bounce(x, d, -130, 130);
  else             y = bounce(y, d, -90, 90);
  LINE(x, y);
}
// Fig. 6: p1=64 · Fig. 10: p1=1024 · Fig. 12: p1=4096

Approximate rendering. The book prints no ALGOL listing for figs. 6–12; the code could not be reconstructed. Left: a reading of the prose (p. 125). The program on p. 124 is ZUFALLSFOLGE 2 — the lower spectrum of fig. 5, not these walks.