d0c17461a7
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> |
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The Go Programming Language
Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.
For documentation about how to install and use Go, visit https://golang.org/ or load doc/install-source.html in your web browser.
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Binary Distribution Notes
If you have just untarred a binary Go distribution, you need to set the environment variable $GOROOT to the full path of the go directory (the one containing this file). You can omit the variable if you unpack it into /usr/local/go, or if you rebuild from sources by running all.bash (see doc/install-source.html). You should also add the Go binary directory $GOROOT/bin to your shell's path.
For example, if you extracted the tar file into $HOME/go, you might put the following in your .profile:
export GOROOT=$HOME/go
export PATH=$PATH:$GOROOT/bin
See https://golang.org/doc/install or doc/install.html for more details.