Infix
[expr, oper, prec, assoc] Infix
can be used with Format
to display certain forms with
user-defined infix notation:
Format[g[x_, y_]] := Infix[{x, y}, "#", 350, Left]
g[a, g[b, c]]
g[g[a, b], c]
g[a + b, c]
g[a * b, c]
g[a, b] + c
g[a, b] * c
Infix[{a, b, c}, {"+", "-"}]