I am attempting to get the following code to compile:
package main
import (
"fmt"
"code.google.com/p/go.text/unicode/norm"
)
func main() {
fmt.Println(norm.IsNormalString("ŋ̊"))
}
I have installed the unicode/norm package. I compile with the command:
go build -o ipa ipa.go
Unfortunately, I get the following error:
# command-line-arguments
./ipa.go:9: undefined: norm.IsNormalString
make: *** [ipa] Error 2
It seems that the package is being imported correctly, but I cannot access any of its members. I have tried changing the method from being called to another from norm, but I still get the error. This leads me to believe that I'm fundamentally misunderstanding something about go's package system.
func (Form) IsNormalString
func (f Form) IsNormalString(s string) bool
IsNormalString returns true if s == f(s).
IsNormalString is not a function, it's a method on type Form. For example,
package main
import (
"code.google.com/p/go.text/unicode/norm"
"fmt"
)
func main() {
fmt.Println(norm.NFC.IsNormalString("ŋ̊"))
}
Output:
true
Related
I'm trying to get GO to compile a simple test script on Windows 10 using GoLand but am running into problems. Here is the code:
package main
import "fmt"
import "C"
import (
"math"
)
func main() {
fmt.Println("working")
}
//export add
func add( a , b int) int {
return a + b
}
//export Cosine
func Cosine(x float64) float64 {
return math.Cos(x)
}
When I comment out the import "C" line the code compiles fine but when its there I get
exec: "gcc": executable file not found in %PATH%
So I installed MinGW and added its bin to the PATH variable so that in a cmd prompt I can run
C:\GolandProjects\LearnGoProject>gcc
gcc: fatal error: no input files
compilation terminated.
However I'm still getting the error. Could anybody suggest how to fix the issue?
I could override the builtin print() function's behavior by defining another print() in scope, as in https://play.golang.org/p/Y2ly31oXU67
Is it possible in go to alter the behavior on-the-fly of an imported function, say fmt.Println()?
If you want to 'alter' a builtin function, look at the very fine monkey patch utility https://github.com/bouk/monkey (And pay attention to the warnings, it's only really useful in test functions, and I for one reject any prod code that imports that package)
Import a different package with name "fmt" and implement whatever functions you need in that package. Here's an example:
File go.mod:
module test
File main.go
package main
import (
"test/fmt"
)
func main() {
fmt.Println("Hello, playground")
}
File fmt/fmt.go:
package fmt
import (
"fmt"
"log"
)
func Println(format string, args ...interface{}) {
msg := fmt.Sprintf(format, args...)
log.Printf(msg)
}
Run it on the playground.
The code in this answer does not modify the imported function as asked in the question.
I can't understand why this :/
I tried go get -u ** with every url that I found.
Thanks
Golang:
$ go version
go version go1.13.3 windows/amd64
Source test:
package main
import (
"fmt"
"cloud.google.com/go/datastore"
)
var client *datastore.Client
func main() {
fmt.Println("Work")
}
Error:
$ go run main.go
# google.golang.org/grpc/internal/transport
..\..\..\..\google.golang.org\grpc\internal\transport\http_util.go:270:23: cannot use hf (type "vendor/golang.org/x/net/http2/hpack".HeaderField) as type
"golang.org/x/net/http2/hpack".HeaderField in argument to d.processHeaderField
..\..\..\..\google.golang.org\grpc\internal\transport\http_util.go:675:23: cannot use "golang.org/x/net/http2/hpack".NewDecoder(http2InitHeaderTableSize,
nil) (type *"golang.org/x/net/http2/hpack".Decoder) as type *"vendor/golang.org/x/net/http2/hpack".Decoder in assignment
Go requires you make use of any package that you import. In this case you are importing "cloud.google.com/go/datastore" but not doing anything with it. The global variable that you declared is also not being used. Since it seems you are just trying to test, so I would recommend you do something with it (atleast print it). Like-
package main
import (
"fmt"
"cloud.google.com/go/datastore"
)
var client *datastore.Client
func main() {
fmt.Println(client)
}
I have put a small code file in $GOPATH which is ~/go/src. Here I have made a folder mysrc and there I have kept a file mytest.go, which is as follows:
package mytest
import ("fmt")
func myfn(){
fmt.Println("My own fn")
}
I try to import above code with following file:
package main
import ("mysrc")
main(){
myfn()
}
When I try to run above file, I get error:
# command-line-arguments
./useMyfn.go:3:1: syntax error: non-declaration statement outside function body
Where is the problem and how can it be solved? Thanks for your help.
Edit: I corrected the main fn to func main() but now the errors are:
# command-line-arguments
./useMyfn.go:2:9: imported and not used: "mysrc" as mytest
./useMyfn.go:4:2: undefined: myfn
You need to do few things
I suggest to use a package name that the name is same with the folder name.
The myfn() function need to be exported. How to do it: simply set the first character of the function name to uppercase.
package mysrc // <-- 1
import (
"fmt"
)
func Myfn() { // <-- 2
fmt.Println("My own fn")
}
The func keyword is required before main() statement.
To access a function from other package, you need to write down the package name before the function name. In this context it'll be mysrc.Myfn().
package main
import (
"mysrc"
)
func main() { // <-- 3
mysrc.Myfn() // <-- 4
}
I have created a library by the name libfastget which is in the src with my program as
src
|-libfastget
| |-libfastget.go
|
|-MainProgram
|-main.go
and the libfastget exports a funtion fastget as follows
package libfastget
import (
"fmt"
"io"
)
func fastget(urlPtr *string, nPtr *int, outFilePtr *string) download {
.....
return dl
}
When I use the library in my main program
package main
import (
"fmt"
"net/http"
"os"
"libfastget"
"path/filepath"
"strings"
"flag"
"time"
)
func uploadFunc(w http.ResponseWriter, r *http.Request) {
n:=libfastget.fastget(url,4,filename)
}
}
I get the following error upon trying to build with go build
# FServe
./main.go:94: cannot refer to unexported name libfastget.fastget
./main.go:94: undefined: libfastget.fastget
The strange thing is that the library file libfastget.a is present in the pkg folder.
you would need to make your function exportable with an uppercase for its name:
func Fastget(...
Used as:
n:=libfastget.Fastget(url,4,filename)
The spec mentions: "Exported identifiers":
An identifier may be exported to permit access to it from another package. An identifier is exported if both:
the first character of the identifier's name is a Unicode upper case letter (Unicode class "Lu"); and
the identifier is declared in the package block or it is a field name or method name.
All other identifiers are not exported.
to export a function into another package the function identifier must start with a capital letter.
I recently started learning GO Lang (2 days back)
And what I found was you need to setup a workspace folder to make the local packages import into other projects or main.go files. I'm using VS Code editor. Please correct me if Im wrong, but this setup works fine for me.
Inside your bash_profile OR .zshrc file add below lines, update the GOPATH as per your folder path.
export GOPATH=~/projects/GO_PROJECTS
export PATH=$PATH:$GOPATH/bin:$PATH
and this is my sayHello.go file, please note to be able to export a function the func name should start with a CapitalCase SayHello
package utils
import "fmt"
func SayHello() {
fmt.Println("Hello, Ajinkya")
}
and now I am able to import utils package into main.go file
package main
import (
"go_proj1/utils"
)
func main() {
utils.SayHello()
}
set the current directory as GOPATH
or you can use local import as follows
move your main.go to the ../ directory to the libfastget.go.
i mean the files looks like:
src
|-libfastget
| |-libfastget.go
|
|-main.go
import "./libfastget"