code review 99420048: fmt: fix floating-point padding once and for all

fmt: fix floating-point padding once and for all
Rewrite formatFloat to be much simpler and clearer and
avoid the tricky interaction with padding.
The issue refers to complex but the problem is just floating-point.
The new tests added were incorrectly formatted before this fix.
Fixes issue 8064.

[r, 2014-05-21 17:43:58]

Hello rsc (cc: golang-codereviews@googlegroups.com),

I'd like you to review this change to
https://code.google.com/p/go/

[jscrockett01, 2014-05-21 17:52:56]

Is there still a width issue?

https://codereview.appspot.com/99420048/diff/1/src/pkg/fmt/fmt_test.go
File src/pkg/fmt/fmt_test.go (right):

https://codereview.appspot.com/99420048/diff/1/src/pkg/fmt/fmt_test.go#newcod...
src/pkg/fmt/fmt_test.go:558: {"%+010.2f", -104.66 - 440.51i,
"(-000104.66-00440.51i)"},
The first four expected outputs are one char longer than the last four expected
outputs. ??

[r, 2014-05-21 17:57:59]

Hello rsc@golang.org, jscrockett01@gmail.com (cc:
golang-codereviews@googlegroups.com),

Please take another look.

[jscrockett01, 2014-05-21 18:00:40]

LGTM

Thanks.

[rsc, 2014-05-21 18:44:41]

LGTM

https://codereview.appspot.com/99420048/diff/20001/src/pkg/fmt/format.go
File src/pkg/fmt/format.go (right):

https://codereview.appspot.com/99420048/diff/20001/src/pkg/fmt/format.go#newc...
src/pkg/fmt/format.go:366: sign := byte('+')
I found it confusing to have both sign and slice[0] and to use each at different
times.
I also found 'slice' confusing; better to say what it is - the comments call it
the number, so 'num'.
I also found the slice[1] == '+' test confusing: if AppendFloat could do that,
we wouldn't need the [0:1] trick.
Suggestion:

// Format number, reserving space for leading + sign if needed.
num := strconv.AppendFloat(f.intbuf[0:1], v, verb, prec, n)
if num[1] == '-' {
    num = num[1:]
} else {
    num[0] = '+'
}

,s/slice/num/g
,s/sign/num[0]/g

[r, 2014-05-21 19:30:17]

almost  - you need to check for num[0]=='+' as well, because Inf does that.

[r, 2014-05-21 19:30:46]

*** Submitted as https://code.google.com/p/go/source/detail?r=e8b79e17dc85 ***

fmt: fix floating-point padding once and for all
Rewrite formatFloat to be much simpler and clearer and
avoid the tricky interaction with padding.
The issue refers to complex but the problem is just floating-point.
The new tests added were incorrectly formatted before this fix.
Fixes issue 8064.

LGTM=jscrockett01, rsc
R=rsc, jscrockett01
CC=golang-codereviews
https://codereview.appspot.com/99420048