CODEWITHSUNDEEP
go
BojanT
BojanT

Reputation: 801

Golang bug or intended feature on map literals?

Just started to learn Go and I need map of string string, that I initialize literally.

mapa := map[string]string{
        "jedan":"one",
        "dva":"two"
       }

But compiler is complaining syntax error: need trailing comma before newline in composite literal

So I had to add coma after "two", or delete a new line and have } after last value for compiler to be happy

Is this intended behavior of code style?

EDIT: to be clear follwing will compile and work

mapa := map[string]string{
        "jedan":"one",
        "dva":"two"  }

go version go1.4.2 darwin/amd64 Mac OSX 10.9.5

Upvotes: 26

Views: 16190

Answers (3)

willy blord
willy blord

Reputation: 1

mapa :=[]map{ "jedan":"one", "dva":"two" }

Upvotes: 0

thwd
thwd

Reputation: 24808

Go has semicolons, but you don't see them because they're inserted automatically by the lexer.

Semicolon insertion rules:

a semicolon is automatically inserted into the token stream at the end of a non-blank line if the line's final token is

  • an integer, floating-point, imaginary, rune, or string literal

So this:

mapa := map[string]string{
    "jedan": "one",
    "dva":   "two"
}

is actually:

mapa := map[string]string{
    "jedan": "one",
    "dva":   "two";  // <- semicolon
}

Which is invalid Go.

Upvotes: 49

Elwinar
Elwinar

Reputation: 9509

Yes it is. And you should choose the added comma.

It is much more simple to edit map/slice literals that way : you can copy-paster, move items around without worrying about the fact that the last item shouldn't be followed by a comma.

In fact, you can also do the same in PHP, javascript, and many other languages.

Upvotes: 16

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