1. The length function

The manual indicates that, for example,

length({{1,2}, {3,4}, {5,6}})   -- 3 

but what should

length({{}}) 

return?

The answer is 1, but why is it not 0?

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2. Re: The length function

dr_can said...

The answer is 1, but why is it not 0?

Because that sequence contains one item: a sequence whose length is zero.

Here's another example:

sequence item1 = {} 
sequence item2 = {} 
sequence item3 = {} 
 
sequence items = { item1, item2, item3 } 
? length( items ) -- contains 3 items 

-Greg

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3. Re: The length function

dr_can said...

The manual indicates that, for example,

length({{1,2}, {3,4}, {5,6}})   -- 3 

but what should

length({{}}) 

return?

The answer is 1, but why is it not 0?

Consider

sequence s1 = {} 
sequence s2 = {s1} 
 
? length(s2) -- returns 1 
? length(s1) -- returns 0 

Now, s2 is a sequence and s2[1] is s1. It is not empty in itself. The sequence s1 is empty however. Finally s2 is equivalent to

{{}} 

SD Pringle

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