ADDED   lib/geo/pythagoras.cpp
Index: lib/geo/pythagoras.cpp
==================================================================
--- lib/geo/pythagoras.cpp
+++ lib/geo/pythagoras.cpp
@@ -0,0 +1,8 @@
+// Enumerate coprime pythagoras triangles
+
+for(int m=1;; ++m)
+for(int n=1; n<m; ++n) if(((m^n)&1) && gcd(m,n)==1)
+{
+	int a = m*m-n*n, b = 2*m*n, c = m*m+n*n;
+	if(a>b) swap(a,b);
+}