| // Copyright 2009 The Go Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style |
| // license that can be found in the LICENSE file. |
| |
| package eval |
| |
| import ( |
| "bignum" |
| ) |
| |
| // TODO(austin): Maybe add to bignum in more general form |
| func ratToString(rat *bignum.Rational) string { |
| n, dnat := rat.Value() |
| d := bignum.MakeInt(false, dnat) |
| w, frac := n.QuoRem(d) |
| out := w.String() |
| if frac.IsZero() { |
| return out |
| } |
| |
| r := frac.Abs() |
| r = r.Mul(bignum.Nat(1e6)) |
| dec, tail := r.DivMod(dnat) |
| // Round last digit |
| if tail.Cmp(dnat.Div(bignum.Nat(2))) >= 0 { |
| dec = dec.Add(bignum.Nat(1)) |
| } |
| // Strip zeros |
| ten := bignum.Nat(10) |
| for !dec.IsZero() { |
| dec2, r2 := dec.DivMod(ten) |
| if !r2.IsZero() { |
| break |
| } |
| dec = dec2 |
| } |
| out += "." + dec.String() |
| return out |
| } |
