# 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(Realvalue,Sideside)

voidapplyBeforeApplying(TridiagonalOperator&) const

voidapplyAfterApplying(Array&) const

voidapplyBeforeSolving(TridiagonalOperator&,Array&rhs) const

voidapplyAfterSolving(Array&) const

voidsetTime(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).