Added possibility to select random number within range

README.md

@@ -281,3 +281,5 @@ Specifying positions in cacmb can be done through a variety of ways. Examples of
 
 `rand` - Returns a random position that lies within the simulation cell.
 
+`rand[val1:val2]` - returns a random position that lies within the range
+

src/subroutines.f90

@@ -172,20 +172,33 @@ module subroutines
         return
     end subroutine parse_ori_vec
 
-    subroutine parse_pos(i, pos_string, pos)
+    recursive subroutine parse_pos(i, pos_string, pos)
         !This subroutine parses the pos command allowing for command which include inf
         integer, intent(in) ::  i !The dimension of the position
         character(len=100), intent(in) :: pos_string !The position string
         real(kind=dp), intent(out) :: pos !The output parsed position value
 
         integer :: iospara
-        real(kind=dp) :: rand
+        real(kind=dp) :: rand, rone, rtwo
+        character(len=100) :: cone, ctwo
 
         iospara = 0
         if(trim(adjustl(pos_string)) == 'inf') then 
             pos=box_bd(2*i)
         else if(trim(adjustl(pos_string)) == '-inf') then
             pos=box_bd(2*i-1)
+
+        else if (trim(adjustl(pos_string)) == 'rand') then 
+            call random_number(rand)
+            pos = (box_bd(2*i)-box_bd(2*i-1))*rand + box_bd(2*i-1)
+
+        else if (index(pos_string,'rand')>0) then 
+            call random_number(rand)
+            cone = pos_string(index(pos_string, '[')+1:index(pos_string,':')-1)
+            call parse_pos(i, cone, rone)
+            ctwo = pos_string(index(pos_string, ':')+1:index(pos_string,']')-1)
+            call parse_pos(i, ctwo, rtwo)
+            pos = (rtwo - rone)*rand + rone            
         else if ((index(pos_string,'-') > 0).and.(index(pos_string,'inf')>0)) then 
             !Now extract the number we are reducing from infinity
             if(index(pos_string,'inf') < index(pos_string,'-')) then 
@@ -211,9 +224,6 @@ module subroutines
             end if
             pos = (box_bd(2*i)-box_bd(2*i-1))*pos + box_bd(2*i-1)
 
-        else if (trim(adjustl(pos_string)) == 'rand') then 
-            call random_number(rand)
-            pos = (box_bd(2*i)-box_bd(2*i-1))*rand + box_bd(2*i-1)
         else
             read(pos_string, *, iostat=iospara) pos
         end if