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vtkFunctionParser

Section: Visualization Toolkit Common Classes

# Usage

vtkFunctionParser is a class that takes in a mathematical expression as a char string, parses it, and evaluates it at the specified values of the variables in the input string.

You can use the "if" operator to create conditional expressions such as if ( test, trueresult, falseresult). These evaluate the boolean valued test expression and then evaluate either the trueresult or the falseresult expression to produce a final (scalar or vector valued) value. "test" may contain <,>,=,|,&, and () and all three subexpressions can evaluate arbitrary function operators (ln, cos, +, if, etc)

.SECTION Thanks Thomas Dunne (thoma.nosp@m.s.du.nosp@m.nne@i.nosp@m.wr.u.nosp@m.ni-he.nosp@m.idel.nosp@m.berg..nosp@m.de) for adding code for two-parameter-parsing and a few functions (sign, min, max).

Sid Sydoriak (sxs@l.nosp@m.anl..nosp@m.gov) for adding boolean operations and conditional expressions and for fixing a variety of bugs.

To create an instance of class vtkFunctionParser, simply invoke its constructor as follows

      obj = vtkFunctionParser

# Methods

The class vtkFunctionParser has several methods that can be used. They are listed below. Note that the documentation is translated automatically from the VTK sources, and may not be completely intelligible. When in doubt, consult the VTK website. In the methods listed below, `obj` is an instance of the vtkFunctionParser class.

- `string = obj.GetClassName ()`
- `int = obj.IsA (string name)`
- `vtkFunctionParser = obj.NewInstance ()`
- `vtkFunctionParser = obj.SafeDownCast (vtkObject o)`
- `obj.SetFunction (string function)`
- `string = obj.GetFunction ()`
- `int = obj.IsScalarResult ()` - Check whether the result is a scalar result. If it isn't, then either the result is a vector or an error has occurred.
- `int = obj.IsVectorResult ()` - Check whether the result is a vector result. If it isn't, then either the result is scalar or an error has occurred.
- `double = obj.GetScalarResult ()` - Get a scalar result from evaluating the input function.
- `double = obj.GetVectorResult ()` - Get a vector result from evaluating the input function.
- `obj.GetVectorResult (double result[3])` - Get a vector result from evaluating the input function.
- `obj.SetScalarVariableValue (string variableName, double value)` - Set the value of a scalar variable. If a variable with this name exists, then its value will be set to the new value. If there is not already a variable with this name, variableName will be added to the list of variables, and its value will be set to the new value.
- `obj.SetScalarVariableValue (int i, double value)` - Set the value of a scalar variable. If a variable with this name exists, then its value will be set to the new value. If there is not already a variable with this name, variableName will be added to the list of variables, and its value will be set to the new value.
- `double = obj.GetScalarVariableValue (string variableName)` - Get the value of a scalar variable.
- `double = obj.GetScalarVariableValue (int i)` - Get the value of a scalar variable.
- `obj.SetVectorVariableValue (string variableName, double xValue, double yValue, double zValue)` - Set the value of a vector variable. If a variable with this name exists, then its value will be set to the new value. If there is not already a variable with this name, variableName will be added to the list of variables, and its value will be set to the new value.
- `obj.SetVectorVariableValue (string variableName, double values[3])` - Set the value of a vector variable. If a variable with this name exists, then its value will be set to the new value. If there is not already a variable with this name, variableName will be added to the list of variables, and its value will be set to the new value.
- `obj.SetVectorVariableValue (int i, double xValue, double yValue, double zValue)` - Set the value of a vector variable. If a variable with this name exists, then its value will be set to the new value. If there is not already a variable with this name, variableName will be added to the list of variables, and its value will be set to the new value.
- `obj.SetVectorVariableValue (int i, double values[3])` - Set the value of a vector variable. If a variable with this name exists, then its value will be set to the new value. If there is not already a variable with this name, variableName will be added to the list of variables, and its value will be set to the new value.
- `double = obj.GetVectorVariableValue (string variableName)` - Get the value of a vector variable.
- `obj.GetVectorVariableValue (string variableName, double value[3])` - Get the value of a vector variable.
- `double = obj.GetVectorVariableValue (int i)` - Get the value of a vector variable.
- `obj.GetVectorVariableValue (int i, double value[3])` - Get the value of a vector variable.
- `int = obj.GetNumberOfScalarVariables ()` - Get the number of scalar variables.
- `int = obj.GetNumberOfVectorVariables ()` - Get the number of vector variables.
- `string = obj.GetScalarVariableName (int i)` - Get the ith scalar variable name.
- `string = obj.GetVectorVariableName (int i)` - Get the ith vector variable name.
- `obj.RemoveAllVariables ()` - Remove all the current variables.
- `obj.RemoveScalarVariables ()` - Remove all the scalar variables.
- `obj.RemoveVectorVariables ()` - Remove all the vector variables.
- `obj.SetReplaceInvalidValues (int )` - When ReplaceInvalidValues is on, all invalid values (such as sqrt(-2), note that function parser does not handle complex numbers) will be replaced by ReplacementValue. Otherwise an error will be reported
- `int = obj.GetReplaceInvalidValues ()` - When ReplaceInvalidValues is on, all invalid values (such as sqrt(-2), note that function parser does not handle complex numbers) will be replaced by ReplacementValue. Otherwise an error will be reported
- `obj.ReplaceInvalidValuesOn ()` - When ReplaceInvalidValues is on, all invalid values (such as sqrt(-2), note that function parser does not handle complex numbers) will be replaced by ReplacementValue. Otherwise an error will be reported
- `obj.ReplaceInvalidValuesOff ()` - When ReplaceInvalidValues is on, all invalid values (such as sqrt(-2), note that function parser does not handle complex numbers) will be replaced by ReplacementValue. Otherwise an error will be reported
- `obj.SetReplacementValue (double )` - When ReplaceInvalidValues is on, all invalid values (such as sqrt(-2), note that function parser does not handle complex numbers) will be replaced by ReplacementValue. Otherwise an error will be reported
- `double = obj.GetReplacementValue ()` - When ReplaceInvalidValues is on, all invalid values (such as sqrt(-2), note that function parser does not handle complex numbers) will be replaced by ReplacementValue. Otherwise an error will be reported