| exp | 
 Def (base power) == if power= 0  1 else base (base power-1) fi  (recursive)
 Thm*  n,k: . (n k)    
 
 Thm*  n,k: . (n k)     
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| inject | 
 Def Inj(A; B; f) ==  a1,a2:A. f(a1) = f(a2)   B    a1 = a2
Thm*  A,B:Type, f:(A  B). Inj(A; B; f)   Prop 
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| int_seg | 
 Def {i..j } == {k: | i   k  <  j }
Thm*  m,n: . {m..n }   Type 
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| nat | 
 Def   == {i: | 0 i }
Thm*     Type 
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| surject | 
 Def Surj(A; B; f) ==  b:B.  a:A. f(a) = b
Thm*  A,B:Type, f:(A  B). Surj(A; B; f)   Prop 
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| eq_int | 
 Def i= j == if i=j  true  ; false  fi
Thm*  i,j: . i= j     
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| lelt | 
 Def i   j  <  k == i j  &  j < k
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| le | 
 Def A B ==  B < A
Thm*  i,j: . i j   Prop 
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| not | 
 Def  A == A    False
Thm*  A:Prop. ( A)   Prop 
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