# QuantLib_NeumannBC man page

NeumannBC — Neumann boundary condition (i.e., constant derivative)

## Synopsis

`#include <ql/methods/finitedifferences/boundarycondition.hpp>`

Inherits **BoundaryCondition< TridiagonalOperator >**.

### Public Member Functions

**NeumannBC** (**Real** value, **Side** side)

void **applyBeforeApplying** (**TridiagonalOperator** &) const

void **applyAfterApplying** (**Array** &) const

void **applyBeforeSolving** (**TridiagonalOperator** &, **Array** &rhs) const

void **applyAfterSolving** (**Array** &) const

void **setTime** (**Time**)

### Additional Inherited Members

## Detailed Description

Neumann boundary condition (i.e., constant derivative)

**Warning**The value passed must not be the value of the derivative. Instead, it must be comprehensive of the grid step between the first two points--i.e., it must be the difference between f[0] and f[1].

## Member Function Documentation

### void applyBeforeApplying (TridiagonalOperator &) const [virtual]

This method modifies an operator $ L $ before it is applied to an array $ u $ so that $ v = Lu $ will satisfy the given condition.

Implements **BoundaryCondition< TridiagonalOperator >**.

### void setTime (Time t) [virtual]

This method sets the current time for time-dependent boundary conditions.

Implements **BoundaryCondition< TridiagonalOperator >**.

## Author

Generated automatically by Doxygen for QuantLib from the source code.

## Referenced By

NeumannBC(3) is an alias of QuantLib_NeumannBC(3).