The 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.
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 mupInit()
by calling mupRelease(hParser)
.
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.
new
and delete
for initialization and deinitialization.)
mu::Parser parser;
Setting the expression when using the DLL requires a valid parser handle and a pointer to
const char
pointing to the expression.
mupSetExpr(hParser, szLine);See also: Example3/Example3.cpp.
Setting the expression using the parser class requires a std::string
containing the expression as the
only parameter.
parser.SetExpr(line);See also: Example1/Example1.cpp; Example2/WndMain.cpp; ParserLib/muParserTest.cpp.
Expression evaluation is done by calling the mupEval()
function in the DLL version or the
Eval()
member function of a parser object. When evaluating an expression for the first time
the parser evaluates the expression string directly and creates a bytecode during
this first time evaluation. Every sucessive call to Eval()
will evaluate the bytecode directly
unless you call a function that will silently reset the parser to string parse mode. Some functions
invalidate the bytecode due to possible changes in callback
function pointers or variable addresses. In this way they effectively cause a recreation of the
bytecode during the next call to Eval()
.
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, Eval()
will call the string parsing function which is slow due to all the
necessary syntax checking, variable lookup, and bytecode creation. Once this
function succeeds, Eval()
will change its internal parse function pointer to either
the bytecode parsing function or the const result function which are significantly (approx. 1000 times)
faster. You don't have to worry about this, it's done automatically, just keep in mind that the
first time evaluation of a new formula is significantly slower than any successive call to
Eval()
.
double fVal; fVal = mupEval(hParser);See also: Example3/Example3.cpp.
double fVal; try { fVal = parser.Eval(); } catch (Parser::exception_type &e) { std::cout << e.GetMsg() << endl; }See also: Example1/Example1.cpp; Example2/WndMain.cpp.
Sometimes 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.)
mupDefineNameChars(hParser, "0123456789_" "abcdefghijklmnopqrstuvwxyz" "ABCDEFGHIJKLMNOPQRSTUVWXYZ"); mupDefineOprtChars(hParser, "abcdefghijklmnopqrstuvwxyz" "ABCDEFGHIJKLMNOPQRSTUVWXYZ" "+-*^/?<>=#!$%&|~'_"); mupDefineInfixOprtChars(hParser, "/+-*^?<>=#!$%&|~'_");
parser.DefineNameChars("0123456789_" "abcdefghijklmnopqrstuvwxyz" "ABCDEFGHIJKLMNOPQRSTUVWXYZ"); parser.DefineOprtChars("abcdefghijklmnopqrstuvwxyz" "ABCDEFGHIJKLMNOPQRSTUVWXYZ" "+-*^/?<>=#!$%&|~'_"); parser.DefineInfixOprtChars("/+-*^?<>=#!$%&|~'_");See also: ParserLib/muParser.cpp; ParserLib/muParserInt.cpp.
Custom variables can be defined either explicit in the code by using the DefineVar
function or implicit by the parser. Implicit declaration will call a variable factory function provided by the user. The parser is never the owner of its variables. So you must take care of their destruction in case of dynamic allocation. The general idea is to bind every parser variable to a C++ variable. For this reason, you have to make sure the C++ variable stays valid as long as you process a formula that needs it. Only variables of type double
are supported.
Explicitely 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.
![]() | Defining new Variables will reset the parser bytecode. Do not use this function just for changing the values of variables! It would dramatically reduce the parser performance! Once the parser knows the address of the variable there is no need to explicitely call a function for changing the value. Since the parser knows the address it knows the value too so simply change the C++ variable in your code directly! |
double fVal=0; mupDefineVar(hParser, "a", &fVal);See also: Example3/Example3.cpp.
double fVal=0; parser.DefineVar("a", &fVal);See also: Example1/Example1.cpp; Example2/WndMain.cpp; ParserLib/muParserTest.cpp.
Implicit 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.
![]() | Be aware of name conflicts! Please notice that recognizing the name of an undefined variable is the last step during parser token detection. If the potential variable name starts with identifiers that could be interpreted as a function or operator it will be detected as such most likely resulting in an syntax error. |
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.
mupSetVarFactory(hParser, AddVariable, pUserData);See also: Example3/Example3.cpp.
parser.SetVarFactory(AddVariable, pUserData);See also: Example1/Example1.cpp.
Parser constants can either be values of type double
or string
. Constness
refers to the bytecode. Constants will be stored by their value in the bytecode, not by a reference to
their address. Thus accessing them is faster. They may be optimized away if this is possible.
Defining new constants or changing old ones will reset the parser to string parsing mode thus resetting
the bytecode.
The Names of user defined constants may contain only the following characters: 0-9, a-z, A-Z, _
, and they may not start with a number. Violating this rule will raise a parser error.
// Define value constantsSee also: Example3/Example3.cpp._pi
mupDefineConst(hParser, "_pi", (double)PARSER_CONST_PI); // Define a string constant namedstrBuf
mupDefineStrConst("strBuf", "hello world");
// Define value constantSee also: Example1/Example1.cpp; Example2/WndMain.cpp; ParserLib/muParserTest.cpp._pi
parser.DefineConst("_pi", (double)PARSER_CONST_PI); // Define a string constant namedstrBuf
parser.DefineStrConst("strBuf", "hello world");
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.
The static callback functions must have of either one of the following types:
// 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);
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.
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.
The 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).
a! = a*(a-1)...*2*1
). Another application for postfix operators is their use as multipliers
that can be used for implementing units."!(a<9)"
.
Both postfix and infix operators take callback functions of type fun_type1
like the following:
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).
// Define an infix operator mupDefineInfixOprt(hParser, "!", MyCallback); // Define a postfix operators mupDefinePostfixOprt(hParser, "M", MyCallback);See also:Example3/Example3.cpp.
// 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.
This parser has 15 Built in binary operators. Sometimes it might be necessary to add additional custom binary operators. Examples are shl
or shr
, the "shift left" and "shift right" operators for integer numbers.
In order to add user defined operators you need to assign a name, a callback function of type fun_type2
and a priority for each new binary operator. You are not allowed to overload built in operators, this would result in an error being raised! For instance lets consider the
following callback function which should be assigned to a binary operator:
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:
mupDefineOprt(hParser, "add", pMyAddFun, 0);See also:Example3/Example3.cpp.
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.
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 EnableBuiltInOprt(bool)
function. If you call this function you must add binary operators manually. After all without any operators you won't be able to parse anything useful. User defined operators come with approximately 10% decrease in parsing speed compared to built in operators. There is no way to avoid that. They cause an overhead when calling theeir callback functions. (This is the reason why there are built in operators)
// disable all built in operators parser.EnableBuiltInOprt(false);
Keeping 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:
For querying the variables used in the expression exchange mupGetVarNum(...)
with
mupGetExprVarNum(...)
and mupGetVar(...)
with mupGetExprVar(...)
in the following example. 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.
// 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.
For querying the expression variables exchange parser.GetVar()
with
parser.GetUsedVar()
in the following example.
// 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 constants is similar to querying variables and expression variables.
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.
The parser class provides you with the GetConst()
member function that returns a map structure
with all defined constants. The following code snippet shows how to use it:
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.
The 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 const char
pointer, a reference to int
and a reference
to double
as their arguments.
The const char
pointer points to the current formula position. The second
argument is the index of that position. This value must be increased by the length of the
value entry if one has been found. In that case the value must be written to the third
argument which is of type double
.
The next code snippet shows a sample implementation of a function that reads and
interprets binary values from the expression string. The code is taken from
muParserInt.cpp the implementation of a parser for integer numbers. Binary
numbers must be preceded with a #
(i.e. #1000101
).
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:> (iBits-i) ); a_iPos += i+1; return true; }
mupAddValIdent(hParser, IsBinVal);See also: Example3/Example3.cpp.
parser.AddValIdent(IsBinVal);See also: ParserLib/muParserInt.cpp.
Removing variables and constants can be done all at once using ClearVar
and
ClearConst
. Additionally variables can be removed by name using
RemoveVar
. Since the parser never owns the variables you must take care of
their release yourself if they were dynamically allocated. If you need to browse all
the variables for that purpose have a look at the chapter explaining how to
query parser variables.
// Remove all constants mupClearConst(hParser); // remove all variables mupClearVar(hParser); // remove a single variable by name mupRemoveVar(hParser, "a");
// Remove all constants parser.ClearConst(); // remove all variables parser.ClearVar(); // remove a single variable by name parser.RemoveVar("a");
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 mu::Parser::exception_type
and in the DLL
version they are normal functions.
These functions are:
exception.GetMsg() / mupGetErrorMsg()
- returns the error message.exception.GetExpr() / mupGetExpr()
- returns the current formula (if a formula is set)exception.GetToken() / mupGetErrorToken()
- returns the token associated with the error (if applicable)exception.GetPos() / mupGetErrorPos()
- returns the current formula position (if applicable)exception.GetCode() / mupGetErrorCode()
- returns the error code.
The following table lists the parser error codes.
The first column contains the enumeration values as defined in the enumeration mu::EErrorCodes
located in the file muParserError.h. Since they are only accessible from C++ the second column lists
their numeric code and the third column contains the error description.
Enumeration name Value Description ecUNEXPECTED_OPERATOR
0 Unexpected binary operator found ecUNASSIGNABLE_TOKEN
1 Token cant be identified ecUNEXPECTED_EOF
2 Unexpected end of formula. (Example: "2+sin(") ecUNEXPECTED_COMMA
3 An unexpected comma has been found. (Example: "1,23") ecUNEXPECTED_ARG
4 An unexpected argument has been found ecUNEXPECTED_VAL
5 An unexpected value token has been found ecUNEXPECTED_VAR
6 An unexpected variable token has been found ecUNEXPECTED_PARENS
7 Unexpected parenthesis, opening or closing ecUNEXPECTED_STR
8 A string has been found at an inapropriate position ecSTRING_EXPECTED
9 A string function has been called with a different type of argument ecVAL_EXPECTED
10 A numerical function has been called with a non value type of argument ecMISSING_PARENS
11 Missing parens. (Example: "3*sin(3") ecUNEXPECTED_FUN
12 Unexpected function found. (Example: "sin(8)cos(9)") ecUNTERMINATED_STRING
13 unterminated string constant. (Example: "3*valueof("hello)") ecTOO_MANY_PARAMS
14 Too many function parameters ecTOO_FEW_PARAMS
15 Too few function parameters. (Example: "ite(1<2,2)") ecOPRT_TYPE_CONFLICT
16 binary operators may only be applied to value items of the same type ecSTR_RESULT
17 result is a string ecINVALID_NAME
18 Invalid function, variable or constant name. ecBUILTIN_OVERLOAD
19 Trying to overload builtin operator ecINVALID_FUN_PTR
20 Invalid callback function pointer ecINVALID_VAR_PTR
21 Invalid variable pointer ecNAME_CONFLICT
22 Name conflict ecOPT_PRI
23 Invalid operator priority ecDOMAIN_ERROR
24 catch division by zero, sqrt(-1), log(0) (currently unused) ecDIV_BY_ZERO
25 Division by zero (currently unused) ecGENERIC
26 Error that does not fit any other code but is not an internal error ecINTERNAL_ERROR
27 Internal error of any kind.
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
mupError()
. By calling this function you will automatically reset the error flag!
// 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
In case of an error the parser class raises an exception of type Parser::exception_type
. This
class provides you with several member functions that allow querying the exact cause as well as
additional information for the error.
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