How complex can a parameter default expression be?

# P T Withington (18 years ago)

Can it refer to previous parameters? Assign to them? Is this legal?

function foo (a:t = x, b:u = (a = y, z))

Can it refer to previous parameters?  Assign to them?  Is this legal?

   function foo (a:t = x, b:u = (a = y, z))

# Brendan Eich (18 years ago)

On Dec 21, 2007, at 4:53 AM, P T Withington wrote:

Can it refer to previous parameters? Assign to them? Is this legal?

function foo (a:t = x, b:u = (a = y, z))

AFAIK the formal parameters (bound in the variable object of the
activation of foo) are not in scope when default parameters are
computed.

On Dec 21, 2007, at 4:53 AM, P T Withington wrote:

> Can it refer to previous parameters?  Assign to them?  Is this legal?
>
>    function foo (a:t = x, b:u = (a = y, z))

AFAIK the formal parameters (bound in the variable object of the  
activation of foo) are not in scope when default parameters are  
computed.

/be

# Dave Herman (18 years ago)

That seems like an unnecessary restriction, no? Since argument evaluation is already restricted to left-to-right, we could allow default-expressions to refer to earlier arguments without too much trouble, unless I'm missing something obvious.

That seems like an unnecessary restriction, no? Since argument 
evaluation is already restricted to left-to-right, we could allow 
default-expressions to refer to earlier arguments without too much 
trouble, unless I'm missing something obvious.

Dave

Brendan Eich wrote:
> On Dec 21, 2007, at 4:53 AM, P T Withington wrote:
> 
>> Can it refer to previous parameters?  Assign to them?  Is this legal?
>>
>>    function foo (a:t = x, b:u = (a = y, z))
> 
> AFAIK the formal parameters (bound in the variable object of the  
> activation of foo) are not in scope when default parameters are  
> computed.
> 
> /be
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