DbU/Unit description

Fixed point numbers management. More...

Classes
class	Hurricane::DbU
	DataBase Unit managment (API). More...

Detailed Description

Fixed point numbers management.

Introduction

The DbU class provides the DbU::Unit type for modelling geometric length, that is abscissas, ordinates, widths, offsets and a set of functions to convert DbU::Unit to and from external coordinates.

Remarks

The DbU class contains only static methods, and is not meant to be instanciated. The working type is DbU::Unit.

The DbU class manage three king of length :

• DbU::Unit : the working type. It is currently associated to a long integer and a precision/resolution. This way all numbers are bound to the same precision (unlike floating point numbers) preventing rounding errors.
• Real length : length, expressed in steps of founder grid. We have the straight relation ship : grid = unit * resolution
• Symbolic length : length, expressed in lambdas. A lambda is an even multiple of the founder grid step. lambda = grid / lambdaPerGrid

Precision

It is possible to choose (once for all) the precision with which unit values are stored.

This precision represents the maximal number of decimal digits allowed (it applies globally to all units). Therefore for a precision of 3, the unit will represent a value of 0.001 and the founder grid value 23.54 will be represented by a unit equal to 23540.

Related functions :

• DbU::getPrecision()
• DbU::getMaximalPrecision()
• DbU::setPrecision()

Resolution

The resolution is associated to the precision. Indeed it represents the external value associated to the smallest unit, that is the value returned by getGrid(Unit::db(1)).

Related functions : DbU::getResolution()

Grids per Lambda ratio

Set the ratio between grids and lambdas. This must be an even integer. Once sets, musn't be changed.

Related functions :

• DbU::setGridsPerLambda()
• DbU::getGridsPerLambda()

Grid

Thoses function are closely related to editors. They allow to restrict to positions on a grid. We support three kind of grid, real, symbolic and user defined.

• DbU::getRealSnapGridStep
• DbU::getOnRealSnapGrid
• DbU::setRealSnapGridStep
• DbU::getSymbolicSnapGridStep
• DbU::getOnSymbolicSnapGrid
• DbU::setSymbolicSnapGridStep
• DbU::getOnCustomGrid
• DbU::getOnPhysicalGrid

Translators

Translate a DbU::Unit into grid or lambda length :

• long DbU::toDb (DbU::Unit u)
• double DbU::toGrid (DbU::Unit u)
• double DbU::toLambda (DbU::Unit u)
• double DbU::toPhysical (DbU::Unit u, UnitPower p)

Translate a lambda length into a DbU::Unit :

• DbU::Unit DbU::fromDb (long v)
• DbU::Unit DbU::fromGrid (double v)
• DbU::Unit DbU::fromLambda (double v)
• DbU::Unit DbU::fromPhysical (double v, UnitPower p)