The Go Language (PART-7)


Declarations


There are four major kinds of declarations:

  1. var,

  2. const,

  3. type,

  4. func

A Go program is stored in one or more files whose names end in .go. Each file begins with a package declaration that says what package the file is part of. The package declaration is followed by any import declarations, and then a sequence of package-level declarations of types, variables, constants, and functions, in any order. For example, this program declares a constant, a function, and a couple of variables:


package main

import "fmt"

const boilingF = 212.0

func main() {
    var f = boilingF
    var c = (f - 32) * 5 / 9
    fmt.Printf("boiling point = %g°F or %g°C\n", f, c)
    // Output:
    // boiling point = 212°F or 100°C
}

The constant boilingF is a package-level declaration (as is main), whereas the variables f and c are local to the function main. The name of each package-level entity is visible not only throughout the source file that contains its declaration, but throughout all the files of the package. By contrast, local declarations are visible only within the function in which they are declared and perhaps only within a small part of it.


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