fmt: support sharp flag for float and complex value printing
Added an alternate form of printing floats and complex values
by specifying the sharp flag.
Output formatted using the the verbs v, e, E, f, F, g and G in
combination with the sharp flag will always include a decimal point.
The alternate form specified by the sharp flag for %g and %G verbs
will not truncate trailing zeros and assume a default precision of 6.
Fixes #18857.
Change-Id: I4d776239e06d7a6a90f2d8556240a359888cb7c3
Reviewed-on: https://go-review.googlesource.com/37051
Reviewed-by: Rob Pike <r@golang.org>
diff --git a/src/fmt/format.go b/src/fmt/format.go
index f770483..d4b92f8 100644
--- a/src/fmt/format.go
+++ b/src/fmt/format.go
@@ -480,6 +480,46 @@
f.zero = oldZero
return
}
+ // The sharp flag forces printing a decimal point for non-binary formats
+ // and retains trailing zeros, which we may need to restore.
+ if f.sharp && verb != 'b' {
+ digits := 0
+ switch verb {
+ case 'v', 'g', 'G':
+ digits = prec
+ // If no precision is set explicitly use a precision of 6.
+ if digits == -1 {
+ digits = 6
+ }
+ }
+
+ // Buffer pre-allocated with enough room for
+ // exponent notations of the form "e+123".
+ var tailBuf [5]byte
+ tail := tailBuf[:0]
+
+ hasDecimalPoint := false
+ // Starting from i = 1 to skip sign at num[0].
+ for i := 1; i < len(num); i++ {
+ switch num[i] {
+ case '.':
+ hasDecimalPoint = true
+ case 'e', 'E':
+ tail = append(tail, num[i:]...)
+ num = num[:i]
+ default:
+ digits--
+ }
+ }
+ if !hasDecimalPoint {
+ num = append(num, '.')
+ }
+ for digits > 0 {
+ num = append(num, '0')
+ digits--
+ }
+ num = append(num, tail...)
+ }
// We want a sign if asked for and if the sign is not positive.
if f.plus || num[0] != '+' {
// If we're zero padding to the left we want the sign before the leading zeros.
