/ Levenshtein distance 
/ http://www.kx.com/a/k/examples/pm.k

x is"as"
y is "awash"

p0 x y is f/[&1+#y;x=\:y;1+!#x]
 where f x y z is z(1+&)\(1_x)&(-1_x)-y

p1 x y is f/[!1+#y;x=\:y;1+!#x]
 where f x y z is z(1+&)\(1_x)&(-1_x)-y

x is"ctagc"
y is"tgac"@draw 100000(4)

r0 x y
 where (r0 x y is(!1+#y)+f/[-!1+#y;x=\:y;1+!#x]) 
 where f x y z is &\z,(1+1_x)&(-1_x)-y

r1 x y
 where (r1 x y is(!1+#y)+f/[&1+#y;x=\:y;1+!#x])
 where f x y z is &\z,(1+1_x)&(-1_x)-y

\

x:"as";y:"awash"
p0:{{z(1+&)\(1_ x)&(-1_ x)-y}/[&1+#y;x=\:y;1+!#x]}      /partial
p1:{{z(1+&)\(1_ x)&(-1_ x)-y}/[!1+#y;x=\:y;1+!#x]}      /total

x:"ctagc";y:"tgac" 100000 _draw 4                       / amino acid pattern
r0:{w+{&\z,(1+1_ x)&(-1_ x)-y}/[-w:!1+#y;x=\:y;1+!#x]}
r1:{(!1+#y)+{&\z,(1+1_ x)&(-1_ x)-y}/[&1+#y;x=\:y;1+!#x]}