extraction of elements of tuples

问题

Given one list with one tuple:

[{4,1,144}]

How to extract the first element of the tuple:

element(1,lists:nth(1,L))

Do you have a simpler solution?

回答1:

Try this:

1> A = [{3,1,1444}].
[{3,1,1444}]
2> [{X, _, _}] = A.
[{3,1,1444}]
3> X.
3
4> 

回答2:

Given that you get exactly what you state, a list with one tuple, even easier would be (using element/2)

element(1, hd(L)).

A pattern matching variant like shk suggested is probably even nicer, depending on the context.

回答3:

you could also consider using records syntax if you want some semantics embedded into your tuples

-record(x, {y, z}).

1> A = #x{y=b, z=c}.
2> A#x.y.
b

all records are in fact tuples and you dont have to worry about order of elements in that tuple nor about adding/removing elements.

来源：https://stackoverflow.com/questions/4819506/extraction-of-elements-of-tuples