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Simulate length function to get the length of a list
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Simulate length function to get the length of a list
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I'm trying to simulate the Length function in Mathematica v.8 to get the length of a list. Given this facts:
- Empty list is represented as {}
- l = Rest[l] assigns to l (which is a list) the list l without the first element
- a While loop
It's my first year using mathematica and I'm not too good at this so there's probably something (or everything) wrong with what I'm doing:
Ej1[l_List] := Module[{i, v},
v = {{}};
i = 1;
While[l != v, l = Rest[l]; i++]
Return[i]
]
l={a,b,c,d,e};
When I try to run it the loop never ends and it gives me this warnings:
Set::shape: Lists {a,b,c,d,e} and {b,c,d,e} are not the same shape. >>
Set::shape: Lists {a,b,c,d,e} and {b,c,d,e} are not the same shape. >>
Set::shape: Lists {a,b,c,d,e} and {b,c,d,e} are not the same shape. >>
General::stop: Further output of Set::shape will be suppressed during this calculation. >>
The main problems were that you were trying to modify the input variable, l, which is not possible, and you had a missing semi-colon.
Ej1[l_List] := Module[{i = 0, v = {}, thisl},
thisl = l;
While[thisl != v, thisl = Rest[thisl]; i++];
i]
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