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/**
* @file device_formula.cpp
* @brief Function for filling generator buffer using a mathematical formula.
* This is kept in its own file as exprtk.hpp takes forever to compile.
*
* Copyright (C) 2021 Clyne Sullivan
*
* Distributed under the GNU GPL v3 or later. You should have received a copy of
* the GNU General Public License along with this program.
* If not, see <https://www.gnu.org/licenses/>.
*/
#include "stmdsp.hpp"
#include "exprtk.hpp"
#include <algorithm>
#include <random>
#include <string_view>
#include <vector>
static std::random_device randomDevice;
std::vector<stmdsp::dacsample_t> deviceGenLoadFormulaEval(const std::string& formulaString)
{
double x = 0;
exprtk::symbol_table<double> symbol_table;
exprtk::function_compositor<double> compositor (symbol_table);
exprtk::expression<double> expression;
exprtk::parser<double> parser;
symbol_table.add_constants();
symbol_table.add_variable("x", x);
symbol_table.add_function("random",
[](double l, double h) -> double {
return std::uniform_real_distribution<double>(l, h)(randomDevice);
});
compositor.add(exprtk::function_compositor<double>::function()
.name("square")
.var("X")
.expression("ceil(sin(pi*X))"));
compositor.add(exprtk::function_compositor<double>::function()
.name("triangle")
.var("X")
.expression("ceil(sin(pi*X))*(X-floor(X))+ceil(-sin(pi*X))*(-X-floor(-X))"));
compositor.add(exprtk::function_compositor<double>::function()
.name("pulse")
.var("L")
.var("X")
.expression("if(X<=L,1,0)"));
expression.register_symbol_table(symbol_table);
parser.compile(formulaString, expression);
const auto genFun = [&x, &expression] {
const auto s = std::clamp(expression.value(), -1., 1.) * 2048. + 2048.;
++x;
return static_cast<stmdsp::dacsample_t>(std::min(s, 4095.));
};
std::vector<stmdsp::dacsample_t> samples (stmdsp::SAMPLES_MAX);
std::generate(samples.begin(), samples.end(), genFun);
return samples;
}
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