pub fn index(input: &str) -> IResult<&str, char>
index = a | b | c | d | e | f | g | h | i | j | k | l |m | n | o | p | q | r | s | t | u | v | w | x |y | z;
a
b
c
d
e
f
g
h
i
j
k
l
m
n
o
p
q
r
s
t
u
v
w
x
y
z