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Start page Features Build instructions Math parser interface Current version |
The parser interfaceThe following section gives an overview of the public parser member functions as well as of the functions exported by the DLL version of the parser. Parser initialization / deinitialization
[DLL interface]
Create a new instance handle. You can create as many different instance handles as you like. Each will
internally reference a different parser object. When using the DLL it is necessary to manually release
any parser handle created by parser_handle hParser; hParser = mupInit(); // Create a new handle // use the parser... mupRelease(hParser); // Release an existing parser handle Internally a handle is nothing more than a pointer to a parser object casted to a void pointer. [Parser class interface]Code for creating a new parser object. (In case of dynamic allocation usenew and delete
for initialization and deinitialization.)
mu::Parser parser; Setting the expression
[DLL interface]
Setting the expression when using the DLL requires a valid parser handle and a pointer to
mupSetExpr(hParser, szLine);See also: Example3/Example3.cpp. [Parser class interface]
Setting the expression using the parser class requires a parser.SetExpr(line);See also: Example1/Example1.cpp; Example2/WndMain.cpp; ParserLib/muParserTest.cpp. Evaluating an expression
Expression evaluation is done by calling the
Internally there are different evaluation functions. One for parsing from a string, the other for
parsing from bytecode (and a third one used only if the expression can be simplified to a constant).
Initially, [DLL interface]
double fVal; fVal = mupEval(hParser);See also: Example3/Example3.cpp. [Parser class interface]
double fVal; try { fVal = parser.Eval(); } catch (Parser::exception_type &e) { std::cout << e.GetMsg() << endl; }See also: Example1/Example1.cpp; Example2/WndMain.cpp. Defining identifier character setsSometimes it is necessary to change the character sets that are used for token identifiers in order to avoid conflicts. The parser uses three different character sets.
mu::muParser directly you can skip this
section. (The DLL version uses the default implementation internally.)
[DLL interface]
mupDefineNameChars(hParser, "0123456789_" "abcdefghijklmnopqrstuvwxyz" "ABCDEFGHIJKLMNOPQRSTUVWXYZ"); mupDefineOprtChars(hParser, "abcdefghijklmnopqrstuvwxyz" "ABCDEFGHIJKLMNOPQRSTUVWXYZ" "+-*^/?<>=#!$%&|~'_"); mupDefineInfixOprtChars(hParser, "/+-*^?<>=#!$%&|~'_"); [Parser class interface]
parser.DefineNameChars("0123456789_" "abcdefghijklmnopqrstuvwxyz" "ABCDEFGHIJKLMNOPQRSTUVWXYZ"); parser.DefineOprtChars("abcdefghijklmnopqrstuvwxyz" "ABCDEFGHIJKLMNOPQRSTUVWXYZ" "+-*^/?<>=#!$%&|~'_"); parser.DefineInfixOprtChars("/+-*^?<>=#!$%&|~'_");See also: ParserLib/muParser.cpp; ParserLib/muParserInt.cpp. Defining parser variables
Custom variables can be defined either explicit in the code by using the Explicitely defining variablesExplicitely in this context means you have to do add the variables manually it in your application code. So you must know in advance which variables you intend to use. If this is not the case have a look at the section on Implicit creation of new variables.
[DLL interface]The first parameter is a valid parser handle, the second the variable name and the third a pointer to the associated C++ variable.double fVal=0; mupDefineVar(hParser, "a", &fVal);See also: Example3/Example3.cpp. [Parser class interface]The first parameter is the variable name and the second a pointer to the associated C++ variable.double fVal=0; parser.DefineVar("a", &fVal);See also: Example1/Example1.cpp; Example2/WndMain.cpp; ParserLib/muParserTest.cpp. Implicit creation of new variablesImplicit declaration of new variables is only possible by setting a factory function. Implicit creation means that everytime the parser finds an unknown token at a position where a variable could be located it creates a new variable with that name automatically. The necessary factory function must be of type: double* (*facfun_type)(const char*, void*)The first argument to a factory function is the name of the variable found by the parser. The second is a pointer to user defined data. This pointer can be used to provide a pointer to a class that implements the actual factory. By doing this it is possible to use custom factory classes depending on the variable name.
double* AddVariable(const char *a_szName, void *pUserData) { static double afValBuf[100]; static int iVal = 0; std::cout << "Generating new variable \"" << a_szName << "\" (slots left: " << 99-iVal << ")" << endl; // you could also do: // MyFactory *pFactory = (MyFactory*)pUserData; // pFactory->CreateNewVariable(a_szName); afValBuf[iVal++] = 0; if (iVal>=99) throw mu::Parser::exception_type("Variable buffer overflow."); return &afValBuf[iVal]; }See also: Example1/Example1.cpp. In order to add a variable factory use the SetVarFactory functions. The first parameter
is a pointer to the static factory function, the second parameter is optional and represents a pointer
to user defined data. Without a variable factory each undefined variable will cause an undefined token error. Factory
functions can be used to query the values of newly created variables directly from a
database. If you emit errors from a factory function be sure to throw an exception of
type ParserBase::exception_type all other exceptions will be caught internally
and result in an internal error.
[DLL interface]
mupSetVarFactory(hParser, AddVariable, pUserData);See also: Example3/Example3.cpp. [Parser class interface]
parser.SetVarFactory(AddVariable, pUserData);See also: Example1/Example1.cpp. Defining parser constants
Parser constants can either be values of type [DLL interface]
// Define value constantsSee also: Example3/Example3.cpp. [Parser class interface]
// Define value constantSee also: Example1/Example1.cpp; Example2/WndMain.cpp; ParserLib/muParserTest.cpp. Defining parser functions
The parser allows the user to define a variety of different callback functions.
Functions with a fixed number of up to five numeric arguments, functions with
a variable number of numeric arguments and functions taking a sinlge string
argument plus up to two numeric values.
In order to define a parser function you need to specify its name, a pointer
to a static callback function and an optional flag indicating if the function
is volatile. Volatile functions are functions that can not be optimized.
// For fixed number of arguments double (*fun_type1)(double); double (*fun_type2)(double, double); double (*fun_type3)(double, double, double); double (*fun_type4)(double, double, double, double); double (*fun_type5)(double, double, double, double, double); // for a variable number of arguments // first arg: pointer to the arguments // second arg: number of arguments double (*multfun_type)(const double*, int); // for functions taking a single string plus up to two numeric values double (*strfun_type1)(const char *); double (*strfun_type2)(const char *, double); double (*strfun_type3)(const char *, double, double); [DLL interface]When using the DLL version it is necessary to call a seperate function for each type of callback. The following is a list of possible choices. // Add functions taking string parameters that cant be optimized mupDefineStrFun1(hParser, "StrFun1", pStrCallback1, false); mupDefineStrFun2(hParser, "StrFun2", pStrCallback2, false); mupDefineStrFun3(hParser, "StrFun3", pStrCallback3, false); // Add an function with a fixed number of arguments mupDefineFun1(hParser, "fun1", pCallback1, false); mupDefineFun2(hParser, "fun2", pCallback2, false); mupDefineFun3(hParser, "fun3", pCallback3, false); mupDefineFun4(hParser, "fun4", pCallback4, false); mupDefineFun5(hParser, "fun5", pCallback5, false); // Define a function with variable number of arguments mupDefineMultFun(hParser, "MultFun", pMultCallback);See also: Example3.cpp. [Parser class interface]Defining callback functions by using the parser class directly is easier since there is only a single member function that is used for all kinds of callbacks. Since this member function is defined as a template internally it automatically associates the right code to any given type of callback. (As long as this type is listed above) parser.DefineFun("FunName", pCallback, false)See also: Example1/Example1.cpp; ParserLib/muParser.cpp; ParserLib/muParserInt.cpp. Defining parser operatorsThe parser is extensible with different kinds of operators: prefix operators, infix operators and binary operators. Operators can be applied to numerical values only (not to string constants).
Unary operators
Both postfix and infix operators take callback functions of type double MyCallback(double fVal) { return fVal/1000.0; }For defining postfix operators and infix operators you need a valid parser instance, an identifier string, and an optional third parameter marking the operator as volatile (non optimizable). [DLL interface]
// Define an infix operator mupDefineInfixOprt(hParser, "!", MyCallback); // Define a postfix operators mupDefinePostfixOprt(hParser, "M", MyCallback);See also:Example3/Example3.cpp. [Parser class interface]
// Define an infix operator parser.DefineInfixOprt("!", MyCallback); // Define a postfix operators parser.DefinePostfixOprt("m", MyCallback);See also:Example1/Example1.cpp; Example2/WndMain.cpp; muParserTest.cpp. Binary operators
This parser has 15 Built in binary operators. Sometimes it might be necessary to add additional custom binary operators. Examples are double pMyAddFun(double v1, double v2) { return v1+v2; }For the definintion of binary operators you need at least 4 parameters. The first is a valid parser handle, the second is the identifier of the operator, the third is the operator callback function, the fourth is the operator priority and the optional fifth parameter is a flag of type bool marking the operator
as volatile. (The examples below omit the last flag.)
Having defined a proper operator callback function you can add the binary operator with the following code:
[DLL interface]
mupDefineOprt(hParser, "add", pMyAddFun, 0);See also:Example3/Example3.cpp. [Parser class interface]
parser.DefineOprt("add", pMyAddFun, 0);See also:Example1/Example1.cpp; Example2/WndMain.cpp; muParserTest.cpp. The priority value must be greater or equal than zero (lowest possible priority). It controls the operator precedence in the formula. For instance if you want to calculate the formula 1+2*3^4 in a mathemetically correct sense you have to make sure that Addition has a lower priority than multiplication which in turn has a lower priority than the power operator. The most likely cases are that you assign an operator with a low priority of 0 (like and , or , xor ) or a high priority that is larger than 6. (The priority of the power operator (^ ).)
By assigning Priority values already used by built in operators you might introduce unwanted side effects. To avoid this and make the order of calculation clear you must use brackets in these cases. Otherwise the order will be determined by the Formula parsing direction which is from left to right.
Example A: Priority of shl equals priority of an addition; The order of the execution is from left to right.
1 + 2 shl 1 => (1 + 2) shl 1 2 shl 1 + 1 => (s shl 1) + 1Example B: Priority of shl is higher than the one of the addition; shl is executed first.
1 + 2 shl 1 => 1 + (2 shl 1) 2 shl 1 + 1 => (2 shl 1) + 1
If you encounter such conflicts or simply dont need the built in operators these can easily be deactivated using the // disable all built in operators parser.EnableBuiltInOprt(false); Querying parser variablesKeeping track of all variables can be a difficult task. For simplification the parser allows the user to query the variables defined in the parser. There are two different sets of variables that can be accessed:
[DLL interface]
For querying the variables used in the expression exchange // Get the number of variables int iNumVar = mupGetVarNum(a_hParser); // Query the variables for (int i=0; i < iNumVar; ++i) { const char *szName = 0; double *pVar = 0; mupGetVar(a_hParser, i, &szName, &pVar); std::cout << "Name: " << szName << " Address: [0x" << pVar << "]\n"; }See also: Example3/Example3.cpp. [Parser class interface]
For querying the expression variables exchange // Get the map with the variables mu::Parser::varmap_type variables = parser.GetVar(); cout << "Number: " << (int)variables.size() << "\n"; // Get the number of variables mu::Parser::varmap_type::const_iterator item = variables.begin(); // Query the variables for (; item!=variables.end(); ++item) { cout << "Name: " << item->first << " Address: [0x" << item->second << "]\n"; }See also: Example1/Example1.cpp, Example2/WndMain.cpp. Querying parser constantsQuerying parser constants is similar to querying variables and expression variables. [DLL interface]Due to the use of an temporary internal static buffer for storing the variable name in the DLL version this DLL-function is not thread safe. int iNumVar = mupGetConstNum(a_hParser); for (int i=0; i < iNumVar; ++i) { const char *szName = 0; double fVal = 0; mupGetConst(a_hParser, i, &szName, fVal); std::cout << " " << szName << " = " << fVal << "\n"; }See also: Example3/Example3.cpp. [Parser class interface]
The parser class provides you with the mu::Parser::valmap_type cmap = parser.GetConst(); if (cmap.size()) { mu::Parser::valmap_type::const_iterator item = cmap.begin(); for (; item!=cmap.end(); ++item) cout << " " << item->first << " = " << item->second << "\n"; }See also: Example1/Example1.cpp, Example2/WndMain.cpp. Setting custom value recognition callbacksThe parser default implementation (muParser.cpp) scans expressions only for floating point values. Custom value recognition callbacks can be used in order to implement support for binary, hexadecimal or octal numbers. These functions are called during the string parsing and allow the user to scan portions of the original expressions for values. Their callback functions must be of the following type: bool (*identfun_type)(const char_type*, int&, value_type&);If the parser reaches an a position during string parsing that could host a value token it tries to interpret it as such. If that fails the parser sucessively calls all internal value recognition callbacks in order to give them a chance to make sense out of what has been found. If all of them fail the parser continues to check if it is a Variable or another kind of token.
In order to perform the task of value recognition these functions take a bool ParserInt::IsBinVal(const char_type *a_szExpr, int &a_iPos, value_type &a_fVal) { if (a_szExpr[0]!='#') return false; unsigned iVal = 0, iBits = sizeof(iVal)*8; for (unsigned i=0; (a_szExpr[i+1]=='0'||a_szExpr[i+1]=='1')&& iOnce you have the callback you must add it to the parser. This can be done with: [DLL interface]
mupAddValIdent(hParser, IsBinVal);See also: Example3/Example3.cpp. [Parser class interface]
parser.AddValIdent(IsBinVal);See also: ParserLib/muParserInt.cpp. Removing variables or constants
Removing variables and constants can be done all at once using [DLL interface]
// Remove all constants mupClearConst(hParser); // remove all variables mupClearVar(hParser); // remove a single variable by name mupRemoveVar(hParser, "a"); [Parser class interface]
// Remove all constants parser.ClearConst(); // remove all variables parser.ClearVar(); // remove a single variable by name parser.RemoveVar("a"); Error handling
In case of an error both parser class and the parser DLL provide
similar methods for querying the information associated with the
error. In the parser class they are member functions of the associated
exception class These functions are:
The following table lists the parser error codes.
The first column contains the enumeration values as defined in the enumeration
[DLL interface]
Since dynamic libraries with functions exported in C-style can't throw exceptions the DLL version
provides the user with a callback mechanism to raise errors. Simply add a callback function
that does the handling of errors. Additionally you can query the error flag with
// Callback function for errors void OnError() { cout << "Message: " << mupGetErrorMsg() << "\n"; cout << "Token: " << mupGetErrorToken() << "\n"; cout << "Position: " << mupGetErrorPos() << "\n"; cout << "Errc: " << mupGetErrorCode() << "\n"; } ... // Set a callback for error handling mupSetErrorHandler(OnError); // The next function could raise an error fVal = mupEval(hParser); // Test for the error flag if (!mupError()) cout << fVal << "\n";See also: Example3/Example3.cpp [Parser class interface]
In case of an error the parser class raises an exception of type try { ... parser.Eval(); ... } catch(mu::Parser::exception_type &e) { cout << "Message: " << e.GetMsg() << "\n"; cout << "Formula: " << e.GetExpr() << "\n"; cout << "Token: " << e.GetToken() << "\n"; cout << "Position: " << e.GetPos() << "\n"; cout << "Errc: " << e.GetCode() << "\n"; }See also: Example1/Example1.cpp
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