fmt, strconv: document that exponent is always two digits

Except for %b where it is only one.

Fixes #70862

Change-Id: Ic423a799b73bfa534f4083f6544bb9cd639fef06
Reviewed-on: https://go-review.googlesource.com/c/go/+/636915
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Ian Lance Taylor <iant@google.com>

diff --git a/src/fmt/doc.go b/src/fmt/doc.go
index b90db7bedc684bb6b22f7088e528c465974c451d..fa0ffa7f00ccc7c93454c0e9292a7e92df0b84c6 100644 (file)
--- a/src/fmt/doc.go
+++ b/src/fmt/doc.go
@@ -50,6 +50,9 @@ Floating-point and complex constituents:
        %x      hexadecimal notation (with decimal power of two exponent), e.g. -0x1.23abcp+20
        %X      upper-case hexadecimal notation, e.g. -0X1.23ABCP+20
 
+       The exponent is always a decimal integer.
+       For formats other than %b the exponent is at least two digits.
+
 String and slice of bytes (treated equivalently with these verbs):
 
        %s      the uninterpreted bytes of the string or slice

diff --git a/src/strconv/ftoa.go b/src/strconv/ftoa.go
index 6db0d47e0f7ae2e41a89a6382fcf798e60c2c3f9..bfe26366e12c136fbc1954ac0e62cc0b32b6f064 100644 (file)
--- a/src/strconv/ftoa.go
+++ b/src/strconv/ftoa.go
@@ -44,6 +44,8 @@ var float64info = floatInfo{52, 11, -1023}
 // zeros are removed).
 // The special precision -1 uses the smallest number of digits
 // necessary such that ParseFloat will return f exactly.
+// The exponent is written as a decimal integer;
+// for all formats other than 'b', it will be at least two digits.
 func FormatFloat(f float64, fmt byte, prec, bitSize int) string {
        return string(genericFtoa(make([]byte, 0, max(prec+4, 24)), f, fmt, prec, bitSize))
 }