Next: 8 Adapting a new terminal Up: 7 Internal programs Prev: 7.8 Implementation aids Contents

7.9 Unclassed

•       REAL FUNCTION RANDOM(I)
        INTEGER I
  

  generates random   numbers .
  

  On entry:
  

  I < 0: initialization of the generator (we advise abs(I) = "big" first number);

  For I 0, we obtain a real number between 0 and 1.

•       REAL FUNCTION ATANG(Y, X)
        REAL X, Y
  

  This is the same as function  ARC-TANGENT with two arguments, but it does not crash if X and Y equals 0; in this case ATANG(0.,0.) = 0.

  The result is a number between 0. and 2*PI.
  

  Y: corresponds to MODULE * SIN(ALPHA);

  X: corresponds to MODULE * COS(ALPHA).
  

•  
  
        SUBROUTINE CXHULL(X, Y, CRITER, REFPTS, NBPTS, HULL, NBHULL)
        REAL X(NBPTS), Y(NBPTS)
        REAL CRITER(2, NBPTS)
        INTEGER NBPTS, REFPTS(NBPTS), HULL(NBPTS), NBHULL
  

  calculates the convex hull of a collection of points .
  

  On entry:
  

  NBPTS, X(NBPTS), Y(NBPTS): definition of the collection of points;

  CRITER(2, NBPTS) and REFPTS(NBPTS): the work arrays for the sort.
  

  On exit:
  

  HULL(NBHULL): the convex hull of NBHULL points;

  HULL: X and Y references defining the convex hull.
  

  The points in the hull are input by turning in the positive direction.
  

•       REAL FUNCTION CPXLIN(X,Y,N,HULL,NBHULL)
        INTEGER N,NBHULL,HULL(NBHULL)
        REAL X(N),Y(N)
  

  computes the "complexity" of the   polygon X,Y.

  CPXLIN= 2*length of the line/perimeter of the convex hull.
  

  On entry:
  

  X, Y: line through N points;

  HULL: convex hull of NBHULL points.
  

  On exit:
  

  CPXLIN= 2*length of the line/perimeter of the convex hull.
  

•       SUBROUTINE NNUEES(X, Y, Z, N, BX, BY, BZ, NBBARY, CHAINE)
        INTEGER N, NBBARY, CHAINE(N)
        REAL X(N), Y(N), Z(N), BX(NBBARY), BY(NBBARY), BZ(NBBARY)
  

  Algorithm for   dynamic clusters .
  

  On entry:
  

  N Points X, Y, Z and NBBARY initial barycenters BX, BY, BZ.
  

  On exit:
  

  The NBBARY barycenters found: BX, BY, BZ;

  CHAINE(I): which points to the barycenter to which the point X(I), Y(I), Z(I) belongs.
  

•       SUBROUTINE BBLOCS(X, Y, Z, N, BX, BY, BZ, NBBARY, CHAINE)
        INTEGER N, NBBARY, CHAINE(N)
        REAL X(N), Y(N), Z(N), BX(NBBARY), BY(NBBARY), BZ(NBBARY)
  

  On entry:
  

  N points X, Y, Z and NBBARY, the number   of barycenters desired.
  

  On exit:
  

  The NBBARY barycenters found: BX, BY, BZ;

  CHAINE(I): which points to the barycenter to which the point X(I), Y(I), Z(I) belongs.
  

•       INTEGER FUNCTION ISIGNE(I)
        INTEGER I
  

  returns 1 if I > 0, 0 if I = 0 or -1 if I < 0.