Re: Generating a simple hand-coded like recursive descent parser

Tommy Thorn wrote:


> to work, most people think that C is an LALR(1) language or simpler (*).


> (*) It's not. The lexer has to know which names are types, otherwise it
> becomes impossible to tell if the statement
> x * y;
> is a declation of a pointer to x or an expression multiplying x and y.


A more practical example, found in this group already:
      a = (b)-c;
is (b) a type cast, or an expression?


Sorry, I don't remember who "invented" this fine example :-(




As a solution for this problem in my LL(1.5) C parser, I leave the
distinction to a stage between the lexer and parser, inside the
preprocessor. Only in this stage "words" are mapped into keywords,
typenames and other identifiers. The according "symbol" table is
initialized with the C keywords, the preprocessor adds to it all
#defined names, and the parser adds all encountered typedef names. This
procedure works fine, provided that typedefs always have global scope,
as is required in C. C++ makes it more complicated, with namespaces and
local typedefs :-(


DoDi

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