Mathematicians who use postfix notation may write "", meaning first apply and then apply , in keeping with the order the symbols occur in postfix notation, thus making the notation "" ambiguous. Computer scientists may write "" for this, thereby disambiguating the order of composition. To distinguish the left composition operator from a text semicolon, in the Z notation the ⨾ character is used for left relation composition. Since all functions are binary relations, it is correct to use the semicolon for function composition as well (see the article on composition of relations for further details on this notation).