Who Cites count pairs?
count_pairs	Def count(x < y in L | P(x;y)) == sum(if (i < j)P(L[i];L[j]) 1 else 0 fi | i < ||L||; j < ||L||)
	Thm* T:Type, L:T List, P:(TT). count(x < y in L | P(x,y))
select	Def l[i] == hd(nth_tl(i;l))
	Thm* A:Type, l:A List, n:. 0n n < ||l|| l[n] A
nth_tl	Def nth_tl(n;as) == if n0 as else nth_tl(n-1;tl(as)) fi (recursive)
	Thm* A:Type, as:A List, i:. nth_tl(i;as) A List
le_int	Def ij == j < i
	Thm* i,j:. (ij)
lt_int	Def i < j == if i < j true ; false fi
	Thm* i,j:. (i < j)
band	Def pq == if p q else false fi
	Thm* p,q:. (pq)
length	Def ||as|| == Case of as; nil 0 ; a.as' ||as'||+1 (recursive)
	Thm* A:Type, l:A List. ||l||
	Thm* ||nil||
double_sum	Def sum(f(x;y) | x < n; y < m) == sum(sum(f(x;y) | y < m) | x < n)
	Thm* n,m:, f:(nm). sum(f(x,y) | x < n; y < m)
hd	Def hd(l) == Case of l; nil "?" ; h.t h
	Thm* A:Type, l:A List. ||l||1 hd(l) A
	Thm* A:Type, l:A List. hd(l) A
sum	Def sum(f(x) | x < k) == primrec(k;0;x,n. n+f(x))
	Thm* n:, f:(n). sum(f(x) | x < n)
tl	Def tl(l) == Case of l; nil nil ; h.t t
	Thm* A:Type, l:A List. tl(l) A List
primrec	Def primrec(n;b;c) == if n=0 b else c(n-1,primrec(n-1;b;c)) fi (recursive)
	Thm* T:Type, n:, b:T, c:(nTT). primrec(n;b;c) T
bnot	Def b == if b false else true fi
	Thm* b:. b
eq_int	Def i=j == if i=j true ; false fi
	Thm* i,j:. (i=j)

Syntax:

count(x < y in L | P(x;y))

has structure:

count_pairs(L; x,y.P(x;y))

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