User defined functions

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The tutorial consists of more than 200 live examples from 50 sections given separately for JAVA, C# and C++. Each of the examples can be copied and run on your own environment. In addition, mXparser provides an extensive collection of over 500 built-in math functions, expressions and symbols. Familiarize yourself with the scope and the syntax. Live testing is the best way to learn. Good luck! 🙂

Tutorial Math Collection API spec Download

Below is the code for JAVA, C# (the code for C# is almost identical) and C++. To copy the code, double-click inside the frame.

You may also be interested in the following tutorial sections:

Case 1: Fast function definition (performance of creation)

Java/C# code
// JAVA: import org.mariuszgromada.math.mxparser.*;
// C#: using org.mariuszgromada.math.mxparser;
// ...
Function f = new Function("f", "x^2", "x");
Expression e = new Expression("f(2)", f);
mXparser.consolePrintln("Res 1: " + e.getExpressionString() + " = " + e.calculate());
mXparser.consolePrintln("Res 2: f(5) = " + f.calculate(5));
C++ code
#include "org/mariuszgromada/math/mxparser.hpp"
// ...
FunctionPtr f = new_Function("f", "x^2", "x");
ExpressionPtr e = new_Expression("f(2)", f);
mXparser::consolePrintln("Res 1: " + e->getExpressionString() + " = " + e->calculate());
mXparser_consolePrintln("Res 2: f(5) = " + f->calculate(5));
Code result
[mXparser-v.5.2.1] Res 1: f(2) = 4.0
[mXparser-v.5.2.1] Res 2: f(5) = 25.0

Case 2: Handy function constructor, but slower proces of function creation (performance of creation slower, but calculation the same)

Java/C# code
// JAVA: import org.mariuszgromada.math.mxparser.*;
// C#: using org.mariuszgromada.math.mxparser;
// ...
Function f = new Function("f(x) = x^2");
Expression e = new Expression("f(2)", f);
mXparser.consolePrintln("Res 1: " + e.getExpressionString() + " = " + e.calculate());
mXparser.consolePrintln("Res 2: f(5) = " + f.calculate(5));
C++ code
#include "org/mariuszgromada/math/mxparser.hpp"
// ...
FunctionPtr f = new_Function("f(x) = x^2");
ExpressionPtr e = new_Expression("f(2)", f);
mXparser::consolePrintln("Res 1: " + e->getExpressionString() + " = " + e->calculate());
mXparser_consolePrintln("Res 2: f(5) = " + f->calculate(5));
Code result
[mXparser-v.5.2.1] Res 1: f(2) = 4.0
[mXparser-v.5.2.1] Res 2: f(5) = 25.0

Case 3: Function with more parameters

Java/C# code
// JAVA: import org.mariuszgromada.math.mxparser.*;
// C#: using org.mariuszgromada.math.mxparser;
// ...
Function f = new Function("f(a, b, c) = a+b+c");
Expression e = new Expression("f(1,2,3)", f);
mXparser.consolePrintln("Res 1: " + e.getExpressionString() + " = " + e.calculate());
mXparser.consolePrintln("Res 2: f(1,2,3) = " + f.calculate(1,2,3));
C++ code
#include "org/mariuszgromada/math/mxparser.hpp"
// ...
FunctionPtr f = new_Function("f(a, b, c) = a+b+c");
ExpressionPtr e = new_Expression("f(1,2,3)", f);
mXparser::consolePrintln("Res 1: " + e->getExpressionString() + " = " + e->calculate());
mXparser_consolePrintln("Res 2: f(1,2,3) = " + f->calculate(1,2,3));
Code result
[mXparser-v.5.2.1] Res 1: f(1,2,3) = 6.0
[mXparser-v.5.2.1] Res 2: f(1,2,3) = 6.0

Case 4: Function in function

Java/C# code
// JAVA: import org.mariuszgromada.math.mxparser.*;
// C#: using org.mariuszgromada.math.mxparser;
// ...
Function g = new Function("g(x) = 2*x");
Function f = new Function("f(x) = g(x)^2", g);

mXparser.consolePrintln("Res 1: g(1) = " + g.calculate(1));
mXparser.consolePrintln("Res 2: f(1) = " + f.calculate(1));
C++ code
#include "org/mariuszgromada/math/mxparser.hpp"
// ...
FunctionPtr g = new_Function("g(x) = 2*x");
FunctionPtr f = new_Function("f(x) = g(x)^2", g);

mXparser_consolePrintln("Res 1: g(1) = " + g->calculate(1));
mXparser_consolePrintln("Res 2: f(1) = " + f->calculate(1));
Code result
[mXparser-v.5.2.1] Res 1: g(1) = 2.0
[mXparser-v.5.2.1] Res 2: f(1) = 4.0

Case 5: Implementing your own Function Extension

Java/C# code
// JAVA: FunctionExtension interface implementation
// ...
import org.mariuszgromada.math.mxparser.*;

class Addition implements FunctionExtension {
   double x;
   double y;
   public Addition() {
      x = Double.NaN;
      y = Double.NaN;
   }
   public Addition(double x, double y) {
      this.x = x;
      this.y = y;
   }
   public int getParametersNumber() {
      return 2;
   }
   public void setParameterValue(int parameterIndex, double parameterValue) {
      if (parameterIndex== 0) x = parameterValue;
      if (parameterIndex== 1) y = parameterValue;
   }
   public String getParameterName(int parameterIndex) {
      switch (parameterIndex) {
         case 0: return "x";
         case 1: return "y";
         default: return "";
      }
   }
   public double calculate() {
      return x+y;
   }
   public FunctionExtension clone() {
      return new Addition(x, y);
   }
}

// C#: FunctionExtension interface implementation
// ...
using System;
using org.mariuszgromada.math.mxparser;

class Addition : FunctionExtension {
   double x;
   double y;
   public Addition() {
      x = Double.NaN;
      y = Double.NaN;
   }
   public Addition(double x, double y) {
      this.x = x;
      this.y = y;
   }
   public int getParametersNumber() {
      return 2;
   }
   public void setParameterValue(int parameterIndex, double parameterValue) {
      if (parameterIndex== 0) x = parameterValue;
      if (parameterIndex== 1) y = parameterValue;
   }
   public String getParameterName(int parameterIndex) {
      switch (parameterIndex) {
         case 0: return "x";
         case 1: return "y";
         default: return "";
      }
   }
   public double calculate() {
      return x+y;
   }
   public FunctionExtension clone() {
      return new Addition(x, y);
   }
}

// JAVA: import org.mariuszgromada.math.mxparser.*;
// C#: using org.mariuszgromada.math.mxparser;
// ...

// Creating extended function
Function f = new Function("f", new Addition());
mXparser.consolePrintln("f.calculate(1,2) = " + f.calculate(1,2) );

// Using extended function in expression
Expression e = new Expression("f(2,3)", f);
mXparser.consolePrintln(e.getExpressionString() + " = " + e.calculate() );
C++ code
#include "org/mariuszgromada/math/mxparser.hpp"
// ...
class Addition : public FunctionExtension {
private:
    double x;
    double y;

public:
    Addition() {
        x = Double::NaN;
        y = Double::NaN;
    }
    Addition(double x, double y) {
        this->x = x;
        this->y = y;
    }
    int getParametersNumber() override {
        return 2;
    }
    void setParameterValue(int parameterIndex, double parameterValue) override {
        if (parameterIndex == 0) x = parameterValue;
        if (parameterIndex == 1) y = parameterValue;
    }
    StringPtr getParameterName(int parameterIndex) override {
        if (parameterIndex == 0) return S("x");
        if (parameterIndex == 1) return S("y");
        return S("");
    }
    double calculate() override {
        return x+y;
    }
    FunctionExtensionPtr clone() override {
        return std::make_shared<Addition>(x, y);
    }
};

inline FunctionExtensionPtr new_Addition() {
    return std::make_shared<Addition>();
}

inline FunctionExtensionPtr new_Addition(double x, double y) {
    return std::make_shared<Addition>(x, y);
}

// Creating extended function
FunctionExtensionPtr addition = new_Addition();
FunctionPtr f = new_Function("f", addition);
mXparser_consolePrintln("f->calculate(1,2) = " + f->calculate(1,2) );

// Using extended function in expression
ExpressionPtr e = new_Expression("f(2,3)", f);
mXparser::consolePrintln(e->getExpressionString() + " = " + e->calculate() );
Code result
[mXparser-v.5.2.1] f.calculate(1,2) = 3.0
[mXparser-v.5.2.1] f(2,3) = 5.0

Case 6: Getting list of missing user defined functions

Java/C# code
// JAVA: import org.mariuszgromada.math.mxparser.*;
// C#: using org.mariuszgromada.math.mxparser;
// ...
Expression e = new Expression("2sin(pi)+2f(1)g(3,4)+4*x");
mXparser.consolePrintln("syntax = " + e.checkSyntax());
mXparser.consolePrintln(e.getErrorMessage());
mXparser.consolePrintln("List of missing user defined functions:");
for (String fun : e.getMissingUserDefinedFunctions())
   mXparser.consolePrintln("Function '" + fun + "' has to be defined");
mXparser.consolePrintln("List of missing user defined arguments:");
for (String arg : e.getMissingUserDefinedArguments())
   mXparser.consolePrintln("Argument '" + arg + "' has to be defined");
C++ code
#include "org/mariuszgromada/math/mxparser.hpp"
// ...
ExpressionPtr e = new_Expression("2sin(pi)+2f(1)g(3,4)+4*x");
mXparser::consolePrintln("syntax = " + e->checkSyntax());
mXparser::consolePrintln(e->getErrorMessage());
mXparser::consolePrintln("List of missing user defined functions:");
for (const StringPtr &fun : *e->getMissingUserDefinedFunctions())
    mXparser::consolePrintln("Function '" + fun + "' has to be defined");
mXparser::consolePrintln("List of missing user defined arguments:");
for (const StringPtr &arg : *e->getMissingUserDefinedArguments())
    mXparser::consolePrintln("Argument '" + arg + "' has to be defined");
Code result
[mXparser-v.5.2.1] syntax = false
[mXparser-v.5.2.1] [2sin(pi)+2f(1)g(3,4)+4*x]: Starting syntax check...
[2sin(pi)+2f(1)g(3,4)+4*x]: Token 'f', index 10: Invalid token.
[2sin(pi)+2f(1)g(3,4)+4*x]: Token 'g', index 15: Invalid token.
[2sin(pi)+2f(1)g(3,4)+4*x]: Token 'x', index 24: Invalid token.
[2sin(pi)+2f(1)g(3,4)+4*x]: Errors have been found.
[mXparser-v.5.2.1] List of missing user defined functions:
[mXparser-v.5.2.1] Function 'f' has to be defined
[mXparser-v.5.2.1] Function 'g' has to be defined
[mXparser-v.5.2.1] List of missing user defined arguments:
[mXparser-v.5.2.1] Argument 'x' has to be defined

Case 7: Possible conflict between Implied Multiplication and getting list of missing user defined functions + recommended solutions

mXparser has many built-in constants. This list can also be expanded by user-defined arguments. As a result, a list of keywords recognized by mXparser is created. By default, the parser operates in implied multiplication mode. In this case, in many situations, these known constants / arguments will be treated as “hidden” multiplication. This is best illustrated by an example where “e” is a builtin famous Euler’s number.

Java/C# code
// JAVA: import org.mariuszgromada.math.mxparser.*;
// C#: using org.mariuszgromada.math.mxparser;
// ...
Expression e = new Expression("3*CasterAttack(4,5)");
mXparser.consolePrintln("String '" + e.getExpressionString() + "' is interpreted as '" + e.getCanonicalExpressionString() + "'");
mXparser.consolePrintln("List of missing user defined functions:");
for (String fun : e.getMissingUserDefinedFunctions())
   mXparser.consolePrintln("Function '" + fun + "' has to be defined");
mXparser.consolePrintln("List of missing user defined arguments:");
for (String arg : e.getMissingUserDefinedArguments())
   mXparser.consolePrintln("Argument '" + arg + "' has to be defined");
C++ code
#include "org/mariuszgromada/math/mxparser.hpp"
// ...
ExpressionPtr e = new_Expression("3*CasterAttack(4,5)");
mXparser::consolePrintln("String '" + e->getExpressionString() + "' is interpreted as '" + e->getCanonicalExpressionString() + "'");
mXparser::consolePrintln("List of missing user defined functions:");
for (const StringPtr &fun : *e->getMissingUserDefinedFunctions())
    mXparser::consolePrintln("Function '" + fun + "' has to be defined");
mXparser::consolePrintln("List of missing user defined arguments:");
for (const StringPtr &arg : *e->getMissingUserDefinedArguments())
    mXparser::consolePrintln("Argument '" + arg + "' has to be defined");
Code result
[mXparser-v.5.2.1] String '3*CasterAttack(4,5)' is interpreted as '3*Cast*e*rAttack(4,5)'
[mXparser-v.5.2.1] List of missing user defined functions:
[mXparser-v.5.2.1] Function 'rAttack' has to be defined
[mXparser-v.5.2.1] List of missing user defined arguments:
[mXparser-v.5.2.1] Argument 'Cast' has to be defined

Solution #1 – turn off the Implied Multiplication Mode (locally)

Java/C# code
// JAVA: import org.mariuszgromada.math.mxparser.*;
// C#: using org.mariuszgromada.math.mxparser;
// ...
mXparser.consolePrintln("Solution #1");
Expression e = new Expression("3*CasterAttack(4,5)");
e.disableImpliedMultiplicationMode();
mXparser.consolePrintln("String '" + e.getExpressionString() + "' is interpreted as '" + e.getCanonicalExpressionString() + "'");
mXparser.consolePrintln("List of missing user defined functions:");
for (String fun : e.getMissingUserDefinedFunctions())
   mXparser.consolePrintln("Function '" + fun + "' has to be defined");
mXparser.consolePrintln("List of missing user defined arguments:");
for (String arg : e.getMissingUserDefinedArguments())
   mXparser.consolePrintln("Argument '" + arg + "' has to be defined");
C++ code
#include "org/mariuszgromada/math/mxparser.hpp"
// ...
mXparser::consolePrintln("Solution #1");
ExpressionPtr e = new_Expression("3*CasterAttack(4,5)");
e->disableImpliedMultiplicationMode();
mXparser::consolePrintln("String '" + e->getExpressionString() + "' is interpreted as '" + e->getCanonicalExpressionString() + "'");
mXparser::consolePrintln("List of missing user defined functions:");
for (const StringPtr &fun : *e->getMissingUserDefinedFunctions())
    mXparser::consolePrintln("Function '" + fun + "' has to be defined");
mXparser::consolePrintln("List of missing user defined arguments:");
for (const StringPtr &arg : *e->getMissingUserDefinedArguments())
    mXparser::consolePrintln("Argument '" + arg + "' has to be defined");
Code result
[mXparser-v.5.2.1] Solution #1
[mXparser-v.5.2.1] String '3*CasterAttack(4,5)' is interpreted as '3*CasterAttack(4,5)'
[mXparser-v.5.2.1] List of missing user defined functions:
[mXparser-v.5.2.1] Function 'CasterAttack' has to be defined
[mXparser-v.5.2.1] List of missing user defined arguments:

Solution #2 – turn off the Implied Multiplication Mode (globally)

Java/C# code
// JAVA: import org.mariuszgromada.math.mxparser.*;
// C#: using org.mariuszgromada.math.mxparser;
// ...
mXparser.consolePrintln("Solution #2");
mXparser.disableImpliedMultiplicationMode();
Expression e = new Expression("3*CasterAttack(4,5)");
mXparser.consolePrintln("String '" + e.getExpressionString() + "' is interpreted as '" + e.getCanonicalExpressionString() + "'");
mXparser.consolePrintln("List of missing user defined functions:");
for (String fun : e.getMissingUserDefinedFunctions())
   mXparser.consolePrintln("Function '" + fun + "' has to be defined");
mXparser.consolePrintln("List of missing user defined arguments:");
for (String arg : e.getMissingUserDefinedArguments())
   mXparser.consolePrintln("Argument '" + arg + "' has to be defined");
C++ code
#include "org/mariuszgromada/math/mxparser.hpp"
// ...
mXparser::consolePrintln("Solution #2");
mXparser::disableImpliedMultiplicationMode();
ExpressionPtr e = new_Expression("3*CasterAttack(4,5)");
mXparser::consolePrintln("String '" + e->getExpressionString() + "' is interpreted as '" + e->getCanonicalExpressionString() + "'");
mXparser::consolePrintln("List of missing user defined functions:");
for (const StringPtr &fun : *e->getMissingUserDefinedFunctions())
    mXparser::consolePrintln("Function '" + fun + "' has to be defined");
mXparser::consolePrintln("List of missing user defined arguments:");
for (const StringPtr &arg : *e->getMissingUserDefinedArguments())
    mXparser::consolePrintln("Argument '" + arg + "' has to be defined");
Code result
[mXparser-v.5.2.1] Solution #2
[mXparser-v.5.2.1] String '3*CasterAttack(4,5)' is interpreted as '3*CasterAttack(4,5)'
[mXparser-v.5.2.1] List of missing user defined functions:
[mXparser-v.5.2.1] Function 'CasterAttack' has to be defined
[mXparser-v.5.2.1] List of missing user defined arguments:

Solution #3 – remove builtin keyword

Java/C# code
// JAVA: import org.mariuszgromada.math.mxparser.*;
// C#: using org.mariuszgromada.math.mxparser;
// ...
mXparser.consolePrintln("Solution #3");
mXparser.removeBuiltinTokens("e");
Expression e = new Expression("3*CasterAttack(4,5)");
mXparser.consolePrintln("String '" + e.getExpressionString() + "' is interpreted as '" + e.getCanonicalExpressionString() + "'");
mXparser.consolePrintln("List of missing user defined functions:");
for (String fun : e.getMissingUserDefinedFunctions())
   mXparser.consolePrintln("Function '" + fun + "' has to be defined");
mXparser.consolePrintln("List of missing user defined arguments:");
for (String arg : e.getMissingUserDefinedArguments())
   mXparser.consolePrintln("Argument '" + arg + "' has to be defined");
C++ code
#include "org/mariuszgromada/math/mxparser.hpp"
// ...
mXparser::consolePrintln("Solution #3");
mXparser::removeBuiltinTokens("e");
ExpressionPtr e = new_Expression("3*CasterAttack(4,5)");
mXparser::consolePrintln("String '" + e->getExpressionString() + "' is interpreted as '" + e->getCanonicalExpressionString() + "'");
mXparser::consolePrintln("List of missing user defined functions:");
for (const StringPtr &fun : *e->getMissingUserDefinedFunctions())
    mXparser::consolePrintln("Function '" + fun + "' has to be defined");
mXparser::consolePrintln("List of missing user defined arguments:");
for (const StringPtr &arg : *e->getMissingUserDefinedArguments())
    mXparser::consolePrintln("Argument '" + arg + "' has to be defined");
Code result
[mXparser-v.5.2.1] Solution #3
[mXparser-v.5.2.1] String '3*CasterAttack(4,5)' is interpreted as '3*CasterAttack(4,5)'
[mXparser-v.5.2.1] List of missing user defined functions:
[mXparser-v.5.2.1] Function 'CasterAttack' has to be defined
[mXparser-v.5.2.1] List of missing user defined arguments:

Solution #4 – modify builtin keyword

Java/C# code
// JAVA: import org.mariuszgromada.math.mxparser.*;
// C#: using org.mariuszgromada.math.mxparser;
// ...
mXparser.consolePrintln("Solution #4");
mXparser.modifyBuiltinToken("e", "ee");
Expression e = new Expression("3*CasterAttack(4,5)");
mXparser.consolePrintln("String '" + e.getExpressionString() + "' is interpreted as '" + e.getCanonicalExpressionString() + "'");
mXparser.consolePrintln("List of missing user defined functions:");
for (String fun : e.getMissingUserDefinedFunctions())
   mXparser.consolePrintln("Function '" + fun + "' has to be defined");
mXparser.consolePrintln("List of missing user defined arguments:");
for (String arg : e.getMissingUserDefinedArguments())
   mXparser.consolePrintln("Argument '" + arg + "' has to be defined");
C++ code
#include "org/mariuszgromada/math/mxparser.hpp"
// ...
mXparser::consolePrintln("Solution #4");
mXparser::modifyBuiltinToken("e", "ee");
ExpressionPtr e = new_Expression("3*CasterAttack(4,5)");
mXparser::consolePrintln("String '" + e->getExpressionString() + "' is interpreted as '" + e->getCanonicalExpressionString() + "'");
mXparser::consolePrintln("List of missing user defined functions:");
for (const StringPtr &fun : *e->getMissingUserDefinedFunctions())
    mXparser::consolePrintln("Function '" + fun + "' has to be defined");
mXparser::consolePrintln("List of missing user defined arguments:");
for (const StringPtr &arg : *e->getMissingUserDefinedArguments())
    mXparser::consolePrintln("Argument '" + arg + "' has to be defined");
Code result
[mXparser-v.5.2.1] Solution #4
[mXparser-v.5.2.1] String '3*CasterAttack(4,5)' is interpreted as '3*CasterAttack(4,5)'
[mXparser-v.5.2.1] List of missing user defined functions:
[mXparser-v.5.2.1] Function 'CasterAttack' has to be defined
[mXparser-v.5.2.1] List of missing user defined arguments:
Nuget – Package Manager (C#, F#, Visual Basic, …)

Install-Package MathParser.org-mXparser-Version 6.1.1

Nuget – .NET CLI

dotnet add package MathParser.org-mXparser--version 6.1.1

Nuget – Package Reference

<PackageReference Include="MathParser.org-mXparser"Version="6.1.1"/>

Maven – Dependency (Java, Kotlin, Scala, Groovy, …)

<dependency>
<groupid>org.mariuszgromada.math</groupid>
<artifactid>MathParser.org-mXparser</artifactid>
<version>6.1.1</version>
</dependency>

Maven – Gradle

implementation 'org.mariuszgromada.math:MathParser.org-mXparser:6.1.1'

CMake – Dependency / FetchContent (C++, MSVC, LLVM/Clang, GNU/GCC, MinGW, MSYS2, WSL, Windows, Linux, Unix, MacOS)

include(FetchContent)
FetchContent_Declare(
MathParserOrgMxParser
GIT_REPOSITORY https://github.com/mariuszgromada/MathParser.org-mXparser.git
GIT_TAG v.6.1.1
SOURCE_SUBDIR CURRENT/cpp/lib
)
FetchContent_MakeAvailable(MathParserOrgMxParser)
mxparser_link(YourExecutable)

GitHub

git clone https://github.com/mariuszgromada/MathParser.org-mXparser

OTHER DOWNLOAD OPTIONS

Download latest release – v.6.1.0 Sagitara: .NET bin onlyDownload latest release – v.6.1.0 Sagitara: JAVA bin onlyDownload latest release – v.6.1.0 Sagitara: bin + doc

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