mupInit()
by calling mupRelease(hParser)
.
muParserHandle_t hParser; hParser = mupInit(); // Create a new handle // use the parser... mupRelease(hParser); // Release an existing parser handleInternally 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;
const char
pointing to the expression.
mupSetExpr(hParser, szLine);
See also: example2/example2.c.
std::string
containing the expression as the
only parameter.
parser.SetExpr(line);
See also: example1/example1.cpp; src/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. By doing so 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 an expression is significantly slower than any successive call to
Eval()
.
double fVal; fVal = mupEval(hParser);See also: example2/example2.c.
double fVal; try { fVal = parser.Eval(); } catch (Parser::exception_type &e) { std::cout << e.GetMsg() << endl; }See also: example1/example1.cpp.
If the expression contains multiple separated subexpressions the return value of Eval()
/
mupEval()
is the result of the last subexpression. If you need all of the results
use the Eval overload described in the next section.
muParser accepts expressions that are made up of several subexpressions delimited by the function argument separator. For instance take a look at the following expression:
sin(x),y+x,x*x
It is made up of three expression separated by commas hence it will create three return values.
(Assuming the comma is defined as the argument separator). The number of return values as well
as their value can be queried with an overload of the Eval
function. This overload
takes a reference to an integer value for storing the total number of return values and returns
a pointer to an array of value_type
holding the actual values with the first value
at the botton of the array and the last at the top.
int nNum, i; muFloat_t *v = mupEvalMulti(hParser, &nNum); for (i=0; i<nNum; ++i) { printf("v[i]=%2.2f\n", v[i]); }
int nNum; value_type *v = parser.Eval(nNum); for (int i=0; i<nNum; ++i) { std::cout << v[i] << "\n"; }See also: example1/example1.cpp.
The function GetNumResults()
can be used in order to finf out whether a given expression has produced
multiple return values.
The basic idea behind the bulkmode is to minimize the overhead of function calls and loops when using muParser inside of large loops. Each loop turn requires a distinct set of variables and setting these variables followed by calling the evaluation function can by slow if the loop is implemented in a managed language. This overhead can be minimized by precalculating the variable values and calling just a single evaluation function. In reality the bulkmode doesn't make much of a difference when used in C++ but it brings a significant increase in performance when used in .NET applications. If muParser was compiled with OpenMP support the calculation load will be spread among all available CPU cores. When using the bulk mode variable pointers submitted to the DefineVar function must be arrays instead of single variables. All variable arrays must have the same size and each array index represents a distinct set of variables to be used in the expression.
Although the bulk mode does work with standard callback functions it may sometimes be necessary to have additional informations inside a callback function. Especially Informations like the index of the current variable set and the index of the thread performing the calculation may be crucial to the evaluation process. To facilitate this need a special set of callback functions was added.
void CalcBulk() { int nBulkSize = 200, i; // allocate the arrays for variables and return values muFloat_t *x = (muFloat_t*)malloc(nBulkSize * sizeof(muFloat_t)); muFloat_t *y = (muFloat_t*)malloc(nBulkSize * sizeof(muFloat_t)); muFloat_t *r = (muFloat_t*)malloc(nBulkSize * sizeof(muFloat_t)); // initialize the parser and variables muParserHandle_t hParser = mupCreate(muBASETYPE_FLOAT); for (i=0; i<nBulkSize; ++i) { x[i] = i; y[i] = i; r[i] = 0; } // Set up variables and functions and evaluate the expression mupDefineVar(hParser, "x", x); mupDefineVar(hParser, "y", y); mupDefineBulkFun1(hParser, "bulktest", BulkTest); mupSetExpr(hParser, "bulktest(x+y)"); mupEvalBulk(hParser, r, nBulkSize); if (mupError(hParser)) { printf("\nError:\n"); printf("------\n"); printf("Message: %s\n", mupGetErrorMsg(hParser) ); printf("Token: %s\n", mupGetErrorToken(hParser) ); printf("Position: %d\n", mupGetErrorPos(hParser) ); printf("Errc: %d\n", mupGetErrorCode(hParser) ); return; } // Output the result for (i=0; i<nBulkSize; ++i) { printf("%d: bulkfun(%2.2f + %2.2f) = %2.2f\n", i, x[i], y[i], r[i]); } free(x); free(y); free(r); }
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.
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.
![]() |
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: example2/example2.c.
double fVal=0; parser.DefineVar("a", &fVal);See also: example1/example1.cpp; src/muParserTest.cpp.
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: example2/example2.c.
parser.SetVarFactory(AddVariable, pUserData);
See also: example1/example1.cpp.
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.
0-9, a-z, A-Z, _
, and they may not start with a number. Violating this rule will raise a parser error.
// Define value constants _pi mupDefineConst(hParser, "_pi", (double)PARSER_CONST_PI); // Define a string constant named strBuf mupDefineStrConst("strBuf", "hello world");See also: example2/example2.c.
// Define value constant _pi parser.DefineConst("_pi", (double)PARSER_CONST_PI); // Define a string constant named strBuf parser.DefineStrConst("strBuf", "hello world");See also: example1/example1.cpp; src/muParserTest.cpp.
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_type *szName = 0; double *pVar = 0; mupGetVar(a_hParser, i, &szName, &pVar); std::cout << "Name: " << szName << " Address: [0x" << pVar << "]\n"; }See also: example2/example2.c.
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.
int iNumVar = mupGetConstNum(a_hParser); for (int i=0; i < iNumVar; ++i) { const char_type *szName = 0; double fVal = 0; mupGetConst(a_hParser, i, &szName, fVal); std::cout << " " << szName << " = " << fVal << "\n"; }See also: example2/example2.c.
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.
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')&& i<iBits; ++i) { iVal |= (int)(a_szExpr[i+1]=='1') << ((iBits-1)-i); } if (i==0) return false; if (i==iBits) throw exception_type("Binary to integer conversion error (overflow)."); a_fVal = (unsigned)(iVal >> (iBits-i) ); a_iPos += i+1; return true; }Once you have the callback you must add it to the parser. This can be done with:
mupAddValIdent(hParser, IsBinVal);
See also: example2/example2.c.
parser.AddValIdent(IsBinVal);
See also: ParserLib/muParserInt.cpp.
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 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");See also: example2/example2.c
// Remove all constants parser.ClearConst(); // remove all variables parser.ClearVar(); // remove a single variable by name parser.RemoveVar("a");See also: example1/example1.cpp
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_ARG_SEP |
3 | An unexpected argument separator 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. |
ecINVALID_BINOP_IDENT |
19 | Invalid binary operator identifier. |
ecINVALID_INFIX_IDENT |
20 | Invalid infix operator identifier. |
ecINVALID_POSTFIX_IDENT |
21 | Invalid postfix operator identifier. |
ecBUILTIN_OVERLOAD |
22 | Trying to overload builtin operator |
ecINVALID_FUN_PTR |
23 | Invalid callback function pointer |
ecINVALID_VAR_PTR |
24 | Invalid variable pointer |
ecEMPTY_EXPRESSION |
25 | The expression string is empty |
ecNAME_CONFLICT |
26 | Name conflict |
ecOPT_PRI |
27 | Invalid operator priority |
ecDOMAIN_ERROR |
28 | catch division by zero, sqrt(-1), log(0) (currently unused) |
ecDIV_BY_ZERO |
29 | Division by zero (currently unused) |
ecGENERIC |
30 | Error that does not fit any other code but is not an internal error |
ecLOCALE |
31 | Conflict with current locale |
ecUNEXPECTED_CONDITIONAL |
32 | Unexpected if then else operator |
ecMISSING_ELSE_CLAUSE |
33 | Missing else clause |
ecMISPLACED_COLON |
34 | Misplaced colon |
ecINTERNAL_ERROR |
35 | Internal error of any kind. |
mupError()
. Please note that 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: example2/example2.c
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