@1

[]        : " |\t|\n"
[const]   : "[0-9]+" : ~
[plus]    : "\+"
[minus]   : "-"
[times]   : "\*"
[divided] : "/"
[open]    : "\("
[close]   : "\)"

{constant}   : <expression> : [const]
{product}    : <expression> : <expression> [times] <expression>
{quotient}   : <expression> : <expression> [divided] <expression>
{sum}        : <expression> : <expression> [plus] <expression>
{difference} : <expression> : <expression> [minus] <expression>
{priorised}  : <expression> : [open] <expression> [close]

<expression>