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@kjk
Created Nov 5, 2019
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Variables
// :collection Essential Go
package main
import (
"bytes"
"fmt"
"io"
)
// :show start
// declaration of a single top-level variable
var topLevel int64 = 5
// grouping of multiple top-level declarations
var (
intVal int // value is initialized with zero-value
str string = "str" // assigning
// functions are first-class values so can be assigned to variables
// fn is variable of type func(a int) string
// it's uninitialized so is nil (zero-value for function variables)
fn func(a int) string
)
func f() {
// shorthand using local type inference
// type of `i` is int and is inferred from the value
// note: this is not allowed at top-level
i := 4
// grouping inside a function
var (
i2 int
s string
)
// _ is like a variable whose value is discarded. It's called blank identifier.
// Useful when we don't care about one of the values returned by a function
_, err := io.Copy(dst, src) // don't care how many bytes were written
// ...
fmt.Printf(`i: %d
i2: %d
s: %s
err: %v
`, i, i2, s, err)
}
// :show end
var (
dst io.Writer = &bytes.Buffer{}
src io.Reader = &bytes.Buffer{}
)
func main() {
f()
}
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