Printing to screen while in loop

Question

I have this:

(loop for i below x
            do (update-world)
            if (zerop (mod i 1000))
            do (princ #\.))

It is working, except that all the princ invokations arrive at once, at the end. The idea here is that they are a progress indicator, printing a period to the screen every 1000 iterations. This is from the Land of Lisp book, and I'm wondering if expecting printing in the middle of a loop is not a portable expectation?

possible duplicate of [slime prints my (format ...) calls only when called function ends](http://stackoverflow.com/questions/19204332/slime-prints-my-format-calls-only-when-called-function-ends) — Joshua Taylor, Nov 27 '13 at 12:10

score 4 · Accepted Answer · answered Nov 27 '13 at 10:16

4

Add a (finish-output) after the princ.

http://clhs.lisp.se/Body/f_finish.htm

answered Nov 27 '13 at 10:16

Lars Brinkhoff

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`finish-output` isn't the only option, though. There's also `force-output`, as described in [slime prints my (format …) calls only when called function ends](http://stackoverflow.com/q/19204332/1281433) (of which I think this question qualifies as a duplicate). – Joshua Taylor Nov 27 '13 at 12:11

Printing to screen while in loop

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