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A function that performs comparison has a the following very simple virtual code representation.
[[compare
]] = (nil,nil)
The proof of theorem T19 is that the standard silly
prelude
contains the declaration compare = (nil,nil)
. Code in this form
has the following semantics.
For distinct trees x
and y
, [[compare
]] (x,y)
= nil
[[compare
]] (x,x)
= (nil,nil)
In other words, the virtual code (nil,nil)
implements a function
that takes a pair of trees and returns true if and only if they are
equal.
It would be fairly simple to write an equivalent virtual code application that implements this function if it were not realizable in this form by definition of the operator. However, this method is preferable because it saves space in virtual code and has a highly optimized implementation in C.
This document was generated on November 8, 2012 using texi2html 1.82.