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term-read-in --> subterm(1200) full-stop
subterm(N) --> term(M)
{ where M is less than or equal to N }
term(N) --> op(N,fx) subterm(N-1)
{ except in the case of a number }
{ if subterm starts with a (,
op must be followed by layout-text }
| op(N,fy) subterm(N)
{ if subterm starts with a (,
op must be followed by layout-text }
| subterm(N-1) op(N,xfx) subterm(N-1)
| subterm(N-1) op(N,xfy) subterm(N)
| subterm(N) op(N,yfx) subterm(N-1)
| subterm(N-1) op(N,xf)
| subterm(N) op(N,yf)
term(1000) --> subterm(999) , subterm(1000)
term(0) --> functor ( arguments )
{ provided there is no layout-text between
the functor and the ( }
| ( subterm(1200) )
| { subterm(1200) }
| list
| string
| constant
| variable
op(N,T) --> name
{ where name has been declared as an
operator of type T and precedence N }
arguments --> subterm(999)
| subterm(999) , arguments
list --> []
| [ listexpr ]
listexpr --> subterm(999)
| subterm(999) , listexpr
| subterm(999) | subterm(999)
constant --> atom | number
number --> unsigned-number
| sign unsigned-number
| sign inf
| sign nan
unsigned-number --> natural-number | unsigned-float
atom --> name
functor --> name