Verifikation reaktiver Systeme - Universität Kaiserslautern

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Fractions As known from school, each fraction f consists of a pair of integers
(a, b), whose components are known as the numerator a and the denominator b
of a fraction. The latter of the two components b must not be zero; otherwise
the fraction does not have a clear meaning. To make things easier, the sign of a
fraction is always moved to the numerator:
f = a a, b ∈ Int,b>0
b
In HOL, the type of fractions can be defined by the following statement.(In
the proof of the the non-emptiness of the set of fractions, 1 1
is used as witness.)
val frac_tyax = save_thm("frac_tyax", new_type_definition( "frac",
Q.prove(‘?x. (\f:int#int. 0