Commit graph

7 commits

Author SHA1 Message Date
Robert Griesemer
d0c17461a7 go/constant: switch to floating-point representation when fractions become too large
Use two internal representations for Float values (similar to what is done
for Int values). Transparently switch to a big.Float representation when
big.Rat values become unwieldy. This is almost never needed for real-world
programs but it is trivial to create test cases that cannot be handled with
rational arithmetic alone.

As a consequence, the go/constant API semantics changes slightly: Until now,
a value could always be represented in its "smallest" form (e.g., float values
that happened to be integers would be represented as integers). Now, constant
Kind depends on how the value was created, rather than its actual value. (The
reason why we cannot automatically "normalize" values to their smallest form
anymore is because floating-point numbers are not exact in general; and thus
normalization is often not possible in the first place, or would throw away
precision when it is not desired.) This has repercussions as to how constant
Values are used go/types and required corresponding adjustments.

Details of the changes:

go/constant package:
- use big.Rat and big.Float values to represent floating-point values
  (internal change)
- changed semantic of Value.Kind accordingly
- String now returns a short, human-readable form of a value
  (this leads to better error messages in go/types)
- added ToInt, ToFloat, and ToComplex conversion functions
- added ExactString to obtain an exact string form of a value

go/types:
- adjusted and simplified implementation of representableConst
- adjusted various places where Value.Kind was expected to be "smallest"
  by calling the respective ToInt/Float/Complex conversion functions
- enabled 5 disabled tests in stdlib_test.go that now work

api checker:
- print all constant values in a short human-readable form (floats are
  printed in floating-point form), but also print an exact form if it
  is different from the short form
- adjusted test golden file and go.1.1.text reference file

Fixes #11327.

Change-Id: I492b704aae5b0238e5b7cee13e18ffce61193587
Reviewed-on: https://go-review.googlesource.com/17360
Reviewed-by: Alan Donovan <adonovan@google.com>
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
2015-12-14 23:42:01 +00:00
Brad Fitzpatrick
39e004b69e api: update go1.1, except and next.txt with constant values
O_SYNC changes only on linux-arm (and linux-arm-cgo), but
changes to match O_SYNC on linux-{386,amd64} and what Linux
upstream now uses.  See discussion and links on
https://golang.org/cl/13261050/

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/13575045
2013-09-06 12:01:18 -07:00
Russ Cox
54bdfc007f encoding/xml: add, support Marshaler interface
See golang.org/s/go12xml for design.

Repeat of CL 12603044, which was submitted accidentally
and then rolled back.

Fixes #2771.
Fixes #4169.
Fixes #5975.
Fixes #6125.

R=golang-dev
CC=golang-dev
https://golang.org/cl/12919043
2013-08-14 14:58:28 -04:00
Russ Cox
56ce83f7ba undo CL 12603044 / 2ca230b93195
fat fingers - did not intend to submit.
depends on the Unmarshaler CL anyway.

««« original CL description
encoding/xml: add, support Marshaler interface

See golang.org/s/go12xml for design.

Fixes #2771.
Fixes #4169.
Fixes #5975.
Fixes #6125.

R=golang-dev, iant, dan.kortschak
CC=golang-dev
https://golang.org/cl/12603044
»»»

TBR=golang-dev
CC=golang-dev
https://golang.org/cl/12918043
2013-08-14 00:20:55 -04:00
Russ Cox
85f3acd788 encoding/xml: add, support Marshaler interface
See golang.org/s/go12xml for design.

Fixes #2771.
Fixes #4169.
Fixes #5975.
Fixes #6125.

R=golang-dev, iant, dan.kortschak
CC=golang-dev
https://golang.org/cl/12603044
2013-08-14 00:17:42 -04:00
Robert Griesemer
9449c18ac8 cmd/api: rewrite using go/types
- adjusted test files so that they actually type-check
- adjusted go1.txt, go1.1.txt, next.txt
- to run, provide build tag: api_tool

Fixes #4538.

R=bradfitz
CC=golang-dev
https://golang.org/cl/12300043
2013-08-08 14:10:59 -07:00
Brad Fitzpatrick
9e93d5014e api: add go1.1.txt; update cmd/api to use it
R=golang-dev, adg, r
CC=golang-dev
https://golang.org/cl/9250043
2013-05-06 17:25:09 -07:00