Value for a missing key in a map

[c4s4]

Let's consider this code:

map = {"foo": 1, "bar": 2}

println(map["spam"])
if map["spam"] == nil {
	println("is nil")
} else {
	println("is not nil")
}
_, ok = map["spam"]
if ok {
	println("key spam")
} else {
	println("no key spam")
}

This produces following output:

$ anko test.ank 
<nil>
is not nil
no key spam

Which means that:

• map["spam"] returns a value that is nil but doesn't pass value == nil.
• Test _, ok = map["spam"] works as expected, telling that map doesn't have key spam.

I think that code map["key"] should throw an error instead than returning a weird nil value.

[MichaelS11]

The not equal to nil is a bug.

package main

import (
	"fmt"
	"log"

	"github.com/mattn/anko/vm"
)

func main() {
	env := vm.NewEnv()

	err := env.Define("println", fmt.Println)
	if err != nil {
		log.Fatalf("Define error: %v\n", err)
	}

	script := `
a = {"b":"b"}

if a.c == nil {
	println("is nil")
}

if a["c"] == nil {
	println("is nil")
} else {
	println("is not nill")
}
`

	_, err = env.Execute(script)
	if err != nil {
		log.Fatalf("Execute error: %v\n", err)
	}
}

I think throwing an error is going to cause more of a headache then it would help. Most of the time just checking for nil will/should work. For the rest of the time, can use ok syntax.

[MichaelS11]

Map not equal to nil fixed here:
#271

[c4s4]

Thanks for this fix! Le jeu. 26 juil. 2018 à 18:02, MichaelS11 <[email protected]> a écrit :

…

Map not equal to nil fixed here: #271 <#271> — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#272 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABMh_6iiiFIs8Wl6jDMg3KPnqfB8bE6Aks5uKefzgaJpZM4VhpTY> .

-- Michel Casabianca

[mattn]

closable?

[MichaelS11]

@mattn ,
Think this can be closed.

[MichaelS11]

Close?