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Scope rules

# Michael O'Brien (18 years ago)

I'm trying to find the scope rules for constructor initializers and for function parameter default values. If someone could point me to a document or clarify these that would be great.

I've read bits and pieces. For constructor initializers:

class Shape { function Shape(): leftSide = rightSide { }

function render(arg1 = expression) {
}

}

In the constructor initializers, I presume the leftSide has a scope equal to just outside the constructor and the rightSide binds to inside the constructor. Is this right?

Also, can "this" be used in either right or left side?

For function default arguments, is the scope of the expression just outside the function?

Michael

# Jeff Dyer (18 years ago)

On 2/7/08 4:16 PM, Michael O'Brien wrote:

I'm trying to find the scope rules for constructor initializers and for function parameter default values. If someone could point me to a document or clarify these that would be great.

I've read bits and pieces. For constructor initializers:

class Shape { function Shape(): leftSide = rightSide { }

function render(arg1 = expression) {
}

}

In the constructor initializers, I presume the leftSide has a scope equal to just outside the constructor and the rightSide binds to inside the constructor. Is this right?

'leftSide' targets the instance and so must be and instance variable. 'rightSide' has a scope that includes the constructor parameters, class statics and scopes beyond.

Also, can "this" be used in either right or left side?

Since 'this' is implied on the left side and meaningless on the right, I'd say not be both.

For function default arguments, is the scope of the expression just outside the function?

This has been debated recently. I don't recall that there was a resolution. My thinking is is that default parameter expression should be scoped to the scope just outside the function. This is how the RI currently works, FWIW.

# Lars Hansen (18 years ago)

-----Original Message----- From: es4-discuss-bounces at mozilla.org [mailto:es4-discuss-bounces at mozilla.org] On Behalf Of Jeff Dyer Sent: 7. februar 2008 20:54 To: Michael O'Brien; es4-discuss Discuss Subject: Re: Scope rules

On 2/7/08 4:16 PM, Michael O'Brien wrote:

I'm trying to find the scope rules for constructor initializers and for function parameter default values. If someone could point me to a document or clarify these that would be great.

I've read bits and pieces. For constructor initializers:

class Shape { function Shape(): leftSide = rightSide { }

function render(arg1 = expression) {
}

}

In the constructor initializers, I presume the leftSide has a scope equal to just outside the constructor and the rightSide binds to inside the constructor. Is this right?

'leftSide' targets the instance and so must be and instance variable. 'rightSide' has a scope that includes the constructor parameters, class statics and scopes beyond.

Also, can "this" be used in either right or left side?

Since 'this' is implied on the left side and meaningless on the right, I'd say not be both.

For function default arguments, is the scope of the expression just outside the function?

This has been debated recently. I don't recall that there was a resolution. My thinking is is that default parameter expression should be scoped to the scope just outside the function. This is how the RI currently works, FWIW.

I agree. There's utility in left-to-right binding, but for the "let" block statement we went with parallel bindings and I think that makes sense for parameter lists as well.