[taos-glug] how do you do formatted printing in Scheme?

Suppose I want to print a number with four digits of precision, i.e., rounded
to the nearest 1/10000th?

For example, suppose I multiply 3.14159 times two.   I want to display the
result as 6.2832 (not as 6.28318).

I figured one way in Scheme, using "round" and "expt".  But, does anybody know
of a more concise way?

Here's how I did it.  Multiply by 10 to the 4th power, round, then divide the
result by 10 to the 4th.

(define val (* 2 3.14159))
(define rounded_val (/ (round (* val (expt 10 4))) (expt 10 4)))
(display rounded_val)
(newline)

By contrast, C would be something like:

  printf("%.4f\n", 2*3.14159);

Other related posts: