code review 1252045: fmt.Scan, fmt.Scanln: Start of a simple scanning package.

fmt.Scan, fmt.Scanln: Start of a simple scanning API in the fmt package.
Still to do:
	- composite types
	- user-defined scanners
	- format-driven scanning
The package comment will be updated when more of the functionality is in place.

[r, 2010-05-24 20:53:58]

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

I'd like you to review this change.

[rsc1, 2010-05-25 23:48:21]

LGTM

http://codereview.appspot.com/1252045/diff/1/3
File src/pkg/fmt/scan.go (right):

http://codereview.appspot.com/1252045/diff/1/3#newcode32
src/pkg/fmt/scan.go:32: // readRune is a structure to enable reading UTF-8
encoded code points
// TODO: readByteRune for things that can read bytes

http://codereview.appspot.com/1252045/diff/1/3#newcode57
src/pkg/fmt/scan.go:57: if c, w := utf8.DecodeRune(r.buf[0:size]); w == size{
Should use utf8.FullRune to handle malformed encodings correctly.

http://codereview.appspot.com/1252045/diff/1/3#newcode93
src/pkg/fmt/scan.go:93: _ = ssFree <- s
s.rr = nil first

http://codereview.appspot.com/1252045/diff/1/3#newcode135
src/pkg/fmt/scan.go:135: if err == os.EOF {
Not sure EOF is a special case here.
The buffer is non-empty - should use it first before getting to the error.

http://codereview.appspot.com/1252045/diff/1/3#newcode150
src/pkg/fmt/scan.go:150: // Scan parses text read from r, storing successive
white-space-separated
s/white-//
again throughout

http://codereview.appspot.com/1252045/diff/1/3#newcode197
src/pkg/fmt/scan.go:197: real, str = floatPart(str)
Looks like this will parse 1.0.2i as a complex 1.0 + 0.2i
Must have + or - at beginning of str at this point.

http://codereview.appspot.com/1252045/diff/1/3#newcode207
src/pkg/fmt/scan.go:207: func floatPart(str string) (first, last string) {
More checks: must have integer digits or fraction.
Must have digits after e±.

http://codereview.appspot.com/1252045/diff/1/3#newcode320
src/pkg/fmt/scan.go:320: for n, param := range a {
Maybe do s.getToken() once here instead of in some of the getters below.

[r, 2010-05-26 04:02:42]

*** Submitted as http://code.google.com/p/go/source/detail?r=b0cbd8aa908e ***

fmt.Scan, fmt.Scanln: Start of a simple scanning API in the fmt package.
Still to do:
	- composite types
	- user-defined scanners
	- format-driven scanning
The package comment will be updated when more of the functionality is in place.

R=rsc
CC=golang-dev
http://codereview.appspot.com/1252045

http://codereview.appspot.com/1252045/diff/1/3
File src/pkg/fmt/scan.go (right):

http://codereview.appspot.com/1252045/diff/1/3#newcode32
src/pkg/fmt/scan.go:32: // readRune is a structure to enable reading UTF-8
encoded code points
On 2010/05/25 23:48:21, rsc1 wrote:
> // TODO: readByteRune for things that can read bytes
> 

Done.

http://codereview.appspot.com/1252045/diff/1/3#newcode57
src/pkg/fmt/scan.go:57: if c, w := utf8.DecodeRune(r.buf[0:size]); w == size{
On 2010/05/25 23:48:21, rsc1 wrote:
> Should use utf8.FullRune to handle malformed encodings correctly.
>  

Done.

http://codereview.appspot.com/1252045/diff/1/3#newcode93
src/pkg/fmt/scan.go:93: _ = ssFree <- s
On 2010/05/25 23:48:21, rsc1 wrote:
> s.rr = nil first
> 

Done.

http://codereview.appspot.com/1252045/diff/1/3#newcode135
src/pkg/fmt/scan.go:135: if err == os.EOF {
it's a special case. consider scanning a (Reader) string "123" looking for an
integer. we hit EOF in this case, but it's not an error.

http://codereview.appspot.com/1252045/diff/1/3#newcode150
src/pkg/fmt/scan.go:150: // Scan parses text read from r, storing successive
white-space-separated
On 2010/05/25 23:48:21, rsc1 wrote:
> s/white-//
> again throughout
> 
> 

Done.

http://codereview.appspot.com/1252045/diff/1/3#newcode197
src/pkg/fmt/scan.go:197: real, str = floatPart(str)
On 2010/05/25 23:48:21, rsc1 wrote:
> Looks like this will parse 1.0.2i as a complex 1.0 + 0.2i
> Must have + or - at beginning of str at this point.
> 
> 

Done.

http://codereview.appspot.com/1252045/diff/1/3#newcode207
src/pkg/fmt/scan.go:207: func floatPart(str string) (first, last string) {
not needed. this code does not need to handle erroneously formatted floats; atof
will report the error.

http://codereview.appspot.com/1252045/diff/1/3#newcode320
src/pkg/fmt/scan.go:320: for n, param := range a {
On 2010/05/25 23:48:21, rsc1 wrote:
> Maybe do s.getToken() once here instead of in some of the getters below.
> 

Done.