0
inl(u) else inr(u) fi
A,B:Type. sigma_to_union 
(i:
2
if i=0 A else B fi)
(A+B)j == if i=j true ; false fii,j:
. (i=j) 
} == {k:| i 
k < j }m,n:. {m..n} TypeA,B:Type. union_to_sigma (A+B)(i:2if i=0 A else B fi)| Some definitions of interest. | |
| sigma_to_union | 0 inl(u) else inr(u) fi |
| A,B:Type. sigma_to_union (i:2if i=0 A else B fi)(A+B) | |
| eq_int | j == if i=j true ; false fi |
| i,j:. (i=j) | |
| int_seg | } == {k:| i k < j } |
| m,n:. {m..n} Type | |
| union_to_sigma | |
| A,B:Type. union_to_sigma (A+B)(i:2if i=0 A else B fi) |
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