math/big: add example for RoundingMode
Updates #11241
Change-Id: I0614c5a9a7a4c399ad5d664f36c70c3210911905
Reviewed-on: https://go-review.googlesource.com/14356
Reviewed-by: Robert Griesemer <gri@golang.org>
diff --git a/src/math/big/floatexample_test.go b/src/math/big/floatexample_test.go
index 358776e..d135243 100644
--- a/src/math/big/floatexample_test.go
+++ b/src/math/big/floatexample_test.go
@@ -109,3 +109,34 @@
// +Inf 1.2 1
// +Inf +Inf 0
}
+
+func ExampleRoundingMode() {
+ operands := []float64{2.6, 2.5, 2.1, -2.1, -2.5, -2.6}
+
+ fmt.Printf("x ")
+ for mode := big.ToNearestEven; mode <= big.ToPositiveInf; mode++ {
+ fmt.Printf(" %s", mode)
+ }
+ fmt.Println()
+
+ for _, f64 := range operands {
+ fmt.Printf("%4g", f64)
+ for mode := big.ToNearestEven; mode <= big.ToPositiveInf; mode++ {
+ // sample operands above require 2 bits to represent mantissa
+ // set binary precision to 2 to round them to integer values
+ f := new(big.Float).SetPrec(2).SetMode(mode).SetFloat64(f64)
+ format := fmt.Sprintf(" %%%dg", len(mode.String()))
+ fmt.Printf(format, f)
+ }
+ fmt.Println()
+ }
+
+ // Output:
+ // x ToNearestEven ToNearestAway ToZero AwayFromZero ToNegativeInf ToPositiveInf
+ // 2.6 3 3 2 3 2 3
+ // 2.5 2 3 2 3 2 3
+ // 2.1 2 2 2 3 2 3
+ // -2.1 -2 -2 -2 -3 -3 -2
+ // -2.5 -2 -3 -2 -3 -3 -2
+ // -2.6 -3 -3 -2 -3 -3 -2
+}
