add a randomwalking prog

.gitignore

@@ -8,4 +8,5 @@
 
 spirale
 starfield
+randomwalk
 

Makefile

@@ -11,6 +11,9 @@ genplotting.o:	genplotting.f90 Makefile
 starfield:	starfield.f90 Makefile genplotting.o
 	gfortran -Wall $< genplotting.o -o $@
 
+randomwalk:	randomwalk.f90 Makefile genplotting.o
+	gfortran -Wall $< genplotting.o -o $@
+
 # -----------------------------------------------
 
 spirale:	spirale.f90 Makefile genplotting.o

randomwalk.f90

@@ -0,0 +1,36 @@
+!
+!                R A N D O M W A L K
+!        la marche de l'ivrogne qui cherche ses clefs sous
+!        le lampadaire, juste là où il y a de la lumière.
+!
+program randomwalk
+  use genplotting
+  implicit none
+  integer    foo, col
+
+  write (0, '(A)') "----[ genplotting randomwalk ]----"
+  call srand(time())
+  call genp_init (0, 'randomwalk.scratch')
+  do foo=1, 51
+    col = 2 + mod(foo, 4)
+    call do_randomwalk(42, col)
+  enddo
+  call genp_end (0)
+contains
+! ---------------------------------------------------------
+subroutine do_randomwalk(nbre, col)
+  integer, intent(in)         :: nbre, col
+  integer                     :: idx
+  real                        :: px, py, px2, py2
+
+  px = 0.0        ;       py = 0.0
+  call genp_move(px, py)
+  do idx=1, nbre
+    px2 = px + rand(0) - 0.50
+    py2 = py + rand(0) - 0.50
+    call genp_line(px, py, px2, py2, col)
+    px = px2  ;  py = py2
+  enddo
+end subroutine
+! ---------------------------------------------------------
+end program