number->string's precision must be positive

Procedure number->string's precision is required be positive as [1], but

$ ypsilon
Ypsilon 0.9.6-trunk/r503 Copyright (c) 2009 Y.Fujita, LittleWing Company 
Limited.
> (number->string 3.14 10 0)
"3.14"
> (number->string 3.14 10 -1)

error in number->string: expected exact non-negative integer, but got -1, as 
argument 3

irritants:
  (3.14 10 -1)

backtrace:
  0  (number->string 3.14 10 -1)
  ..."/dev/stdin" line 1

> 

[1] http://www.r6rs.org/final/html/r6rs/r6rs-Z-H-14.html#node_idx_578

Original issue reported on code.google.com by tabe.fix...@gmail.com on 14 Aug 2009 at 12:10

david135 / ypsilon

number->string's precision must be positive #122