Looks like somewhere in the middle he/she switched to a different style. Where +, *, etc are treated as infix operators by default; so that you don't have to wr

Looks like somewhere in the middle he/she switched to a different style. Where +, *, etc are treated as infix operators by default; so that you don't have to write `+` anymore. But to treat + as a regular operator, you would write (+).