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Having trouble with variable number of arguments

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Posted by Nick Gammon Australia (23,133 posts) Bio Forum Administrator

Date Reply #15 on Thu 11 Sep 2008 09:31 PM (UTC)

Message

Quote:

c = { [xxx] = "a" } -- assigns "a" to c.q
d = { "xxx" = "a" } -- error: '}' expected near '='

I'd expect the last table to work and have (d.xxx == "a") as a result. Why is -that- assignment not supported?

I think the answer would be, it would be ambiguous.

On the face of it, it would seem reasonable to support stuff like:


t = {
     "a" = 22,    -- t ["a"] = 22
     45 = 68,   -- t [45] = 68
     true = 99,  -- t [true] = 99
    2 + 2 = 55,  -- t [4] = 55
    }

Effectively by allowing any sort of constant there. However then you would expect any expression there too (like in the case of 2 + 2).

Now you hit a big problem:


foo = 42
t = {
     foo = 99,  -- t [42] = 99
    }

The entry "foo" is an expression, which happens to be a variable containing 42. However we are already used to that actually meaning:


foo = 42
t = {
     foo = 99,  -- t ["foo"] = 99
    }

So, exceptions would have to be made, to be consistent with what currently happens. The whole thing would probably become a mess.

- Nick Gammon

www.gammon.com.au, www.mushclient.com

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Posted by

Worstje Netherlands (899 posts) Bio

Date

Reply #16 on Thu 11 Sep 2008 11:04 PM (UTC)

Message

Good reason, I am satisfied. ^_^

(Although I still say it's the wrong way around.. dum dum.)

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Posted by

David Haley USA (3,881 posts) Bio

Date

Reply #17 on Thu 11 Sep 2008 11:33 PM (UTC)

Message

Well, you wouldn't have to allow arbitrary expressions -- you could stick with identifiers and string literals only. Of course, then you have an inconsistency of sorts of only allowing string constants.

David Haley aka Ksilyan
Head Programmer,
Legends of the Darkstone

http://david.the-haleys.org

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