strconv: slightly simplified roundShortest; better comments
Change-Id: If886f15468680f7e1c589873066b4391eb9784b5
Reviewed-on: https://go-review.googlesource.com/14856
Reviewed-by: Alan Donovan <adonovan@google.com>
diff --git a/src/strconv/ftoa.go b/src/strconv/ftoa.go
index 468c37f..9ff5d10 100644
--- a/src/strconv/ftoa.go
+++ b/src/strconv/ftoa.go
@@ -286,25 +286,23 @@
// Now we can figure out the minimum number of digits required.
// Walk along until d has distinguished itself from upper and lower.
for i := 0; i < d.nd; i++ {
- var l, m, u byte // lower, middle, upper digits
+ l := byte('0') // lower digit
if i < lower.nd {
l = lower.d[i]
- } else {
- l = '0'
}
- m = d.d[i]
+ m := d.d[i] // middle digit
+ u := byte('0') // upper digit
if i < upper.nd {
u = upper.d[i]
- } else {
- u = '0'
}
// Okay to round down (truncate) if lower has a different digit
- // or if lower is inclusive and is exactly the result of rounding down.
- okdown := l != m || (inclusive && l == m && i+1 == lower.nd)
+ // or if lower is inclusive and is exactly the result of rounding
+ // down (i.e., and we have reached the final digit of lower).
+ okdown := l != m || inclusive && i+1 == lower.nd
- // Okay to round up if upper has a different digit and
- // either upper is inclusive or upper is bigger than the result of rounding up.
+ // Okay to round up if upper has a different digit and either upper
+ // is inclusive or upper is bigger than the result of rounding up.
okup := m != u && (inclusive || m+1 < u || i+1 < upper.nd)
// If it's okay to do either, then round to the nearest one.
diff --git a/src/strconv/ftoa_test.go b/src/strconv/ftoa_test.go
index 1b4dcd9..0b9f0fe 100644
--- a/src/strconv/ftoa_test.go
+++ b/src/strconv/ftoa_test.go
@@ -18,7 +18,7 @@
s string
}
-func fdiv(a, b float64) float64 { return a / b } // keep compiler in the dark
+func fdiv(a, b float64) float64 { return a / b }
const (
below1e23 = 99999999999999974834176
@@ -94,8 +94,8 @@
{above1e23, 'f', -1, "100000000000000010000000"},
{above1e23, 'g', -1, "1.0000000000000001e+23"},
- {fdiv(5e-304, 1e20), 'g', -1, "5e-324"},
- {fdiv(-5e-304, 1e20), 'g', -1, "-5e-324"},
+ {fdiv(5e-304, 1e20), 'g', -1, "5e-324"}, // avoid constant arithmetic
+ {fdiv(-5e-304, 1e20), 'g', -1, "-5e-324"}, // avoid constant arithmetic
{32, 'g', -1, "32"},
{32, 'g', 0, "3e+01"},
