ref: 2c454342da4593b2457ec4b39958cef9bfcaa0b3
dir: femtolisp/tests/pisum.lsp
(define (pisum)
(dotimes (j 500)
((label sumloop
(lambda (i sum)
(if (> i 10000)
sum
(sumloop (+ i 1) (+ sum (/ (* i i)))))))
1.0 0.0)))