CRuntimeCompiledExpression.cpp

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2020, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */

#include "expr-precomp.h"  // Precompiled headers

#include <mrpt/core/exceptions.h>
#include <mrpt/expr/CRuntimeCompiledExpression.h>
#include <mrpt/system/string_utils.h>
#include <cmath>  // M_PI
#include <cstdlib>
#include <iostream>

#define exprtk_disable_string_capabilities  // Workaround a bug in Ubuntu
// precise's GCC+libstdc++

// Disable some parts of exprtk to build faster and reduce lib size:
#define exprtk_disable_enhanced_features
#define exprtk_disable_superscalar_unroll
#define exprtk_disable_rtl_vecops
#define exprtk_disable_rtl_io_file
#include <mrpt/3rdparty/exprtk.hpp>

using namespace mrpt;
using namespace mrpt::expr;

struct CRuntimeCompiledExpression::ExprVerbose
{
    static CRuntimeCompiledExpression::ExprVerbose& Instance()
    {
        static CRuntimeCompiledExpression::ExprVerbose obj;
        return obj;
    }
    void process(const CRuntimeCompiledExpression& rce, const double ret);

   private:
    bool m_verbose_always_enabled{false};
    std::vector<std::string> m_verbose_matches;
    ExprVerbose()
    {
        const char* sp = ::getenv("MRPT_EXPR_VERBOSE");
        if (nullptr == sp) return;
        const std::string s = mrpt::system::trim(std::string(sp));

        if (s == std::string("1"))
        {
            m_verbose_always_enabled = true;
            return;
        }
        mrpt::system::tokenize(s, "|", m_verbose_matches);
    }
};

// We only need this to be on this translation unit, hence the advantage of
// using our MRPT wrapper instead of the original exprtk sources.
struct CRuntimeCompiledExpression::Impl
{
    exprtk::expression<double> m_compiled_formula;
    std::string m_original_expr_str;
};

CRuntimeCompiledExpression::CRuntimeCompiledExpression()
    : m_impl(mrpt::make_impl<CRuntimeCompiledExpression::Impl>())
{
}

CRuntimeCompiledExpression::~CRuntimeCompiledExpression() = default;

void CRuntimeCompiledExpression::compile(
    /** [in] The expression to be compiled. */
    const std::string& expression,
    /** [in] Map of variables/constants by `name` ->  `value`. The references to
       the values in this map **must** be ensured to be valid thoughout all the
       life of the compiled expression. */
    const std::map<std::string, double>& variables,
    /** A descriptive name of this formula, to be used when generating error
       reports via an  exception, if needed */
    const std::string& expr_name_for_error_reporting)
{
    m_impl->m_original_expr_str = expression;

    exprtk::symbol_table<double> symbol_table;
    for (const auto& v : variables)
    {
        auto& var = const_cast<double&>(v.second);
        symbol_table.add_variable(v.first, var);
    }
    symbol_table.add_constant("M_PI", M_PI);
    symbol_table.add_constants();

    m_impl->m_compiled_formula.register_symbol_table(symbol_table);

    // Compile user-given expressions:
    exprtk::parser<double> parser;
    if (!parser.compile(expression, m_impl->m_compiled_formula))
        THROW_EXCEPTION_FMT(
            "Error compiling expression (name=`%s`): `%s`. Error: `%s`",
            expr_name_for_error_reporting.c_str(), expression.c_str(),
            parser.error().c_str());
}

double CRuntimeCompiledExpression::eval() const
{
    ASSERT_(m_impl);
    double ret = m_impl->m_compiled_formula.value();
    ExprVerbose::Instance().process(*this, ret);
    return ret;
}

void CRuntimeCompiledExpression::register_symbol_table(
    /** [in] Map of variables/constants by `name` ->  `value`. The
       references to the values in this map **must** be ensured to be valid
       thoughout all the life of the compiled expression. */
    const std::map<std::string, double*>& variables)
{
    exprtk::symbol_table<double> symbol_table;
    for (const auto& v : variables)
    {
        auto* var = const_cast<double*>(v.second);
        symbol_table.add_variable(v.first, *var);
    }
    m_impl->m_compiled_formula.register_symbol_table(symbol_table);
}

exprtk::expression<double>& CRuntimeCompiledExpression::get_raw_exprtk_expr()
{
    ASSERT_(m_impl);
    return m_impl->m_compiled_formula;
}
const exprtk::expression<double>&
    CRuntimeCompiledExpression::get_raw_exprtk_expr() const
{
    ASSERT_(m_impl);
    return m_impl->m_compiled_formula;
}

bool CRuntimeCompiledExpression::is_compiled() const
{
    ASSERT_(m_impl);
    return m_impl->m_compiled_formula;
}
const std::string& CRuntimeCompiledExpression::get_original_expression() const
{
    return m_impl->m_original_expr_str;
}

void CRuntimeCompiledExpression::ExprVerbose::process(
    const CRuntimeCompiledExpression& rce, const double ret)
{
    if (!m_verbose_always_enabled && m_verbose_matches.empty()) return;

    const auto& exp = *rce.m_impl.get();

    if (!m_verbose_matches.empty())
    {
        bool matched = false;
        for (const auto& s : m_verbose_matches)
        {
            if (exp.m_original_expr_str.find(s) != std::string::npos)
            {
                matched = true;
                break;
            }
        }
        if (!matched) return;
    }

    std::vector<std::pair<std::string, double>> lst;
    exp.m_compiled_formula.get_symbol_table().get_variable_list(lst);
    // clang-format off
    std::cout << "[CRuntimeCompiledExpression::eval()] DEBUG:\n"
                 "* Expression: "
              << exp.m_original_expr_str << "\n"
                 "* Final value: " << ret << "\n"
                 "* Using these symbols:\n";
    // clang-format on
    for (const auto& v : lst)
        std::cout << " * " << v.first << " = " << v.second << "\n";
}