Comment by digging

3 months ago

I don't write a lot of while loops so this is just a bit unfamiliar to me, but I'm not really understanding how this isn't the same as `do{block}while(condition);`? Could you give a simple example of what kind of work `prepare` is doing?

2 comments

digging

TrianguloY 3 months ago

Think of a producer (a method that returns data each time you request one, like reading a file line by line or extracting the top of a queue for example) that you need to parse and process until you find a special element that means "stop".

Something like

  do{
    raw_data=produce.get()
    data=parse(raw_data)
  }while(data!=STOP){
    process(data)
  }

I'm aware this example can be trivially replaced with a while(data=parse(producer.get())){process(data)} but you are forced to have a method, and if you need both the raw and parsed data at the same time, either you mix them into a wrapper or you need to somehow transfer two variables at the same time from the parse>condition>process

A do-while here also has the same issue, but in this case after you check the condition you can't do any processing afterwards (unless you move the check and process into a single check_and_process method...which you can totally do but again the idea is to not require it)

bandie91 3 months ago

i often want to write:

  do {
    offset = tell(filehandle)
  } while(line = readline(filehandle))
  {
    print "line starts at offset: ", offset
  }