On 03/06/2005 07:59 AM, Pavel Chikulaev wrote:
I'm currently working on library "Lazy".
Library description: Library eases creation of classes which needs lazy evalution and n-arity operators [snip] Library features are: * n-arity operators support; * operator aliasing, such as a + -b will be computed as a - b; [snip] Library's sample usage: [snip] class Matrix { LAZY_CLASS(Matrix) static lazy::type<Matrix> Matrix_; //Similar to Andrei Alexandrescu's [snip] Matrix(LAZY_OP(Matrix_ + Matrix_ * Matrix_)); //ternary operator
//Now enable operators LAZY_ENABLE_OP(Matrix_ = Matrix_ + Matrix_); LAZY_ENABLE_OP(Matrix_ = Matrix_ * Matrix_); LAZY_ENABLE_OP(Matrix_ = -Matrix_); LAZY_ENABLE_OP(Matrix_ = Matrix_ + Matrix_ * Matrix_);
//Actually we can make declaration of lazy operators and enabling them using only one macro e.g. LAZY_CONSTUCTOR(Matrix_ = Matrix_ * Matrix_ * Matrix_);
[snip]
Is there any need of such library?
Maybe. If "aliasing" can convert (a+b+c)*x to a*x+b*x+c*x then maybe it can be used to "normalize" a grammar: X = ('a'|'b'|'c') X | 'd' -> X = 'a'X | 'b'X | 'c'X | 'd' which would enable, I think, conversion to a boolean matrix representation of the First relation of the grammar: X 'a' 'b' 'c' 'd' X 0 1 1 1 1 'a' 0 0 0 0 0 'b' 0 0 0 0 0 'c' 0 0 0 0 0 'd' 0 0 0 0 0 and then the operator* and + could be used to maybe make a lazy transtive closure, First^*, of this relation. Similarly, it could be used for calculation of Last relation and and transitive closure of the transpose of that. These are all needed by the method described here: http://facweb.cs.depaul.edu/tchristopher/grmanl.pdf to generate a parser. In addition to the above, I'd also like to see if the value of a matrix multiplication and addition can be computed at compile time. If so, then I'm guessing that, given enough resources, a spirit grammar (normalized as described above) can be analyzed at compile time and used to generate a parser with compile-time generated look-ahead sets. OK, maybe that's dreaming, but that's me :)