group/vector operation possible? Naive iteration can be expensive when number of elements is huge about cparse

[VinGarcia]

The current implementation of memory management on lists is not very efficient =/. I belive the best way to fix this would be to implement a special type of list made for only for integers, floats, etc that internally would count as a single std::vector.

We could create a special type such as "TokenIntList" etc, for these cases. However, I currently don't have time to spare =/.

If you want to submit a PR for this it would be welcome, but it might be a little complicated 🤔 .

[zxpatric]

Let me see if the naive is acceptable speed wise and how complicated it is to implement TokenIntList. Is there a way that calculator::calculate can cache the equation interpretation so it doesn't have to parse it every time for every tuple? For exmaple, a^2+bc. If there are 3 vectors for a, b, c and each tuple with one element from a, b, c will be called through calculator::calculate("a^2+bc", &vars). My concern is the parsing time of the equation can be long but can also be saved since it needs to be done only once. Any sight on this?

[zxpatric]

Got it. may dig deep into this function and use rpn for naive iteration.

packToken calculator::calculate(const char* expr, TokenMap vars,
const char* delim, const char** rest) {
// Convert to RPN with Dijkstra's Shunting-yard algorithm.
RAII_TokenQueue_t rpn = calculator::toRPN(expr, vars, delim, rest);

TokenBase* ret = calculator::calculate(rpn, vars);

return packToken(resolve_reference(ret));
}

[VinGarcia]

About your first comment: If you compile the expression, i.e. create an instance of the calculator class the parsing is made only on the first time. Then for each consecutive call to eval() it will only execute the code in the context provided by the TokenMap passed as argument and not parse it.

If this was your concern then I might have misunderstood you.

You can see how to do that on the Getting Started page of the Wiki:

• https://github.com/cparse/cparse/wiki/Getting-Started

The easiest way to do it would be like this:

TokenMap vars;
calculator C("my_var = x / 4 + 3");

vars["x"] = 8;
std::cout << C.eval(vars) << std::endl; // 5

vars["x"] = 16;
std::cout << C.eval(vars) << std::endl; // 7

Is this the issue you needed to fix?, If so you can close this issue.

[zxpatric]

Thanks VinGarcia. I did went that way. The speed is o...k for large amount although if there are possibilities to support vectorized operation, the best.