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fmt: get wrong result when using "%.30f" in fmt.Sprintf #47931

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xiaoyang-chen opened this issue Aug 24, 2021 · 1 comment
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fmt: get wrong result when using "%.30f" in fmt.Sprintf #47931

xiaoyang-chen opened this issue Aug 24, 2021 · 1 comment
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@xiaoyang-chen
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xiaoyang-chen commented Aug 24, 2021 •
edited

What version of Go are you using (go version)?

$ go version

go playground. and. go version go1.16.6 darwin/amd64

Does this issue reproduce with the latest release?

unknown, reproduce in go playground and go version go1.16.6 darwin/amd64

What operating system and processor architecture are you using (go env)?

go env Output
$ go env
GO111MODULE="" GOARCH="amd64" GOBIN="" GOCACHE="/Users/xxx/Library/Caches/go-build" GOENV="/Users/xxx/Library/Application Support/go/env" GOEXE="" GOFLAGS="" GOHOSTARCH="amd64" GOHOSTOS="darwin" GOINSECURE="" GOMODCACHE="/Users/xxx/go/pkg/mod" GONOPROXY="" GONOSUMDB="" GOOS="darwin" GOPATH="/Users/xxx/go" GOPRIVATE="" GOPROXY="https://goproxy.io,direct,https://proxy.golang.org,direct" GOROOT="/usr/local/Cellar/go/1.16.6/libexec" GOSUMDB="sum.golang.org" GOTMPDIR="" GOTOOLDIR="/usr/local/Cellar/go/1.16.6/libexec/pkg/tool/darwin_amd64" GOVCS="" GOVERSION="go1.16.6" GCCGO="gccgo" AR="ar" CC="clang" CXX="clang++" CGO_ENABLED="1" GOMOD="/dev/null" CGO_CFLAGS="-g -O2" CGO_CPPFLAGS="" CGO_CXXFLAGS="-g -O2" CGO_FFLAGS="-g -O2" CGO_LDFLAGS="-g -O2" PKG_CONFIG="pkg-config" GOGCCFLAGS="-fPIC -arch x86_64 -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/v8/lqjftghd06x4bdc946hl2gsc0000gn/T/go-build4061609802=/tmp/go-build -gno-record-gcc-switches -fno-common"

What did you do?

fmt.Println(fmt.Sprintf("%.30f", 5.400000*float64(0.400000)))
https://play.golang.org/p/o4ARzVQfsw_0

What did you expect to see?

get. 2.160000000000000000000000000000

What did you see instead?

get 2.160000000000000142108547152020
@xiaoyang-chen xiaoyang-chen changed the title get wrong data when using "%.30f" in fmt.Sprintf fmt: get wrong data when using "%.30f" in fmt.Sprintf Aug 24, 2021
@seankhliao
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Floating points are limited in accuracy and cannot represent all numbers

@xiaoyang-chen xiaoyang-chen changed the title fmt: get wrong data when using "%.30f" in fmt.Sprintf fmt: get wrong result when using "%.30f" in fmt.Sprintf Aug 24, 2021
@golang golang locked and limited conversation to collaborators Aug 24, 2022
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