Loop in PLT Scheme

Question

How can I implement loop in plt-scheme like in java-

for(int i=0;i<10;){
     for(int j=0;j<3;){
          System.out.println(\"\"+j);
          j++;
         


        

Answer 1

The iteration construct in Scheme is "do", you can look it up in the R5RS specification.

The example you gave would look something like this:

(do ((i 0 (+ i 1))) ((> i 9))
  (do ((j 0 (+ j 1))) ((> j 2))
    (display j)
    (newline))
  (display i)
  (newline))

(do ...) is a bit more general than what shows up in this example. You can for example make it return a value instead of just using it for its side effects. It is also possible to have many "counters":

(do ((i 0 (+ i 1) 
     (j 0 (+ j 2)) 
    ((stop? i j) )
   exprs...)