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Example (Continued)

We proceed by structural induction on x:

Case x=nil:
We have to show
forall y in List(T):
   length(append(nil, y)) = length(nil)+length(y).
Take arbitrary y in List(T). We have
length(append(nil, y)) = (definition append)
length(y) =
0+length(y) = (definition length)
length(nil)+length(y).

Author: Wolfgang Schreiner
Last Modification: November 24, 1999

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