3.1. Parallel combinator

When the expressions to be combined are small, write them all on one line.

F | G | H

When the combined expressions are large enough to take up a full line, write one expression per line, with each subsequent expression aligned with the first and preceded by |. Indent the first expression to improve readability.

  long expression 
| long expression
| long expression

A sequence of parallel expressions often form the left hand side of a sequential combinator. Since the sequential combinator has higher precedence, use parentheses to group the combined parallel expressions together.

( expression 
| expression
) >x> 
another expression