Compile time lex + parse + semantic = 300 lines of code

[Regan Heath]

Regan Heath wrote:
> Daniel Keep wrote:
>>
>> Don Clugston wrote:
>>> I've finally released the compile-time parser I mentioned in my
>>> conference presentation.
>>>
>>> http://www.dsource.org/projects/mathextra/browser/trunk/blade/SyntaxTree.d 
>>>
>>>
>>> contains one publicly usable function:
>>>
>>> char [] syntaxtreeof(char [] expression).
>>>
>>> When mixed in, this lexes and parses the expression, determines
>>> precedence and associativity, creating an object of type
>>> AbstractSyntaxTree, which contains a standardized 'placeholder
>>> expression' (eg "A+=(B*C)")
>>> and a symbol table for the variables, constants and functions A,B,C,...
>>> The symbol table includes the type and value for each symbol.
>>> All aliases and compile-time constants are resolved and converted to a
>>> standard form.
>>> All symbols must be reachable from the scope where syntaxtreeof() is
>>> mixed into.
>>>
>>> The created AbstractSyntaxTree is a compile-time constant, so it can be
>>> used for  further compile-time operations and code generation.
>>>
>>> Works for almost any expression (templates, functions, strings, slicing,
>>> struct literals,...); the biggest omission is relational operators.
>>> Less than 300 lines of code in D1.020.
>>> Probably could simplified using __traits in D2.0.
>>> Enjoy.
>>>
>>>
>>> Return type:
>>> -----
>>> struct Symbol {
>>>     char [] type; // the name of the type, as text
>>>     char [] value; // the value, as text. Either the symbol name, or a
>>> literal
>>> }
>>>
>>> // The result of semantic analysis of the original expression
>>> struct AbstractSyntaxTree {
>>>     char [] expression; // syntax tree in Placeholder format, eg 
>>> A+=(B*C)
>>>     Symbol[] symbolTable; // The types and values of A,B,C,...
>>> }
>>> ------
>>>
>>> Example:
>>> -----
>>> import SyntaxTree;
>>>
>>> const foo = "abc";
>>> int bar(real x, char [] s) { return 0; }
>>> struct Duck{};
>>> Duck duck;
>>>
>>> AbstractSyntaxTree a = mixin(syntaxtreeof(`foo*   bar(2.18_3242e+45L,
>>> "xyz") in duck`));
>>
>> Words fail me; I'm going to have to borrow some from Dave Grossman:
>>
>> Sweet mother of double-jeopardy back-stroking in butterscotch with a
>> holy cap-wearing catfish flopping a crime-beat past sweet suffering St.
>> Sebastian on a sousaphone in a short story by Susan Sontag with the
>> great grinning head of John the Baptist in a pork-pie hat stuffed in a
>> rhinestone bowling bag by the Greek goddess Celine in a chariot with
>> dual overhead cams and Silver Fox mudflaps...
>>
>> ...that's impressive.
> 
> This is the sort of thing that needs to be published in a "Check out the 
> crazy sh!t we can do with D" article :D

Clarification; "crazy" as in "crazy cool" :P

Regan