Semantics Influences Parsing

Example: Operator Precedence:

	A + B * C
means:	A + (B * C)
not:	(A + B) * C

Possible solutions:

1. Unambiguous operator precedence grammar.
   Large, ugly grammar and parser.
   In Pascal, the grammar is not large, but lack of precedence forces the programmer to parenthesize:

   
          if ( x > y && y > z ) ...
   
          if x > y and y > z then ...
   

   The Pascal version shown above generates an error; it must be written as:

   
          if (x > y) and (y > z) then ...
   

2. Ambiguous grammar; precedence guides parser.
   Short, simple, clean grammar and parser.