Hi,
I have been continuing with my physical-quantities library over the last year, http://www.servocomm.freeserve.co.uk/Cpp/physical_quantity/index.html and I am now seeking feedback as to whether it is worth putting this forward as a boost library proposal....
*Overview*
The physical-quantity type-family provides methods for modeling physical-quantities in C++ programs. The advantages and extra functionality over inbuilt types used in the role include, compile time dimensional-analysis checking, automatic conversion between units and an increase in source code comprehensibility. The type family includes two types, firstly a type where the units are fixed at compile-time referred to in the text as a ct-quantity and secondly a type where the units can be run-time modified, referred to in the text as an rt-quantity.
The ct-quantity has many similar features to an inbuilt-type:
- concrete type with simple,consistent semantics close to those of inbuilt-types. - aims for speed and code size performance close to that of in-built types. - requires no special framework to use.
*Application areas*
The application areas are very wide, including scientific-engineering, CAD, 3D games programming among many others.
*Future directions*
2D and 3D vector quantities, scene-graphs and scene-modelling, Graphics interface (eg OpenGL), splines and curve analysis, successive approaximation , piecewise differentiation and integration algorithms. finite element analysis, etc etc.
Issues from the previous thread on the library and physical quantities in general
http://aspn.activestate.com/ASPN/Mail/Message/boost/1926782
issue: Angles.
current status: Angles are implemented.There are two types, irrational (ie radians) and rational fractions of revolution ie degrees minutes etc). radians are what you might call a 'weak type'. (Though this behaviour can be modified by a macro switch). They will implicitly decay to (say) double and can be implicitly cast to double. However they also allow implicit conversions to and from degrees etc. hence an implicit conversion from degrees to radians can occur if a function has a radians argument, but not a double argument. They are also useful for output of units. --------------------- issue: Differentiating different but dimensionally equivalent types.
current status: This is implemented. --------------------- issue: Implicit conversions between units.
current status: Implicit conversions are intrinsic. They are practical instinctive and useful. --------------------- issue: You should be using mpl.
current status: Hopefully I will be able to get hold of the
Hi Andy, I just read your post in boost.devel list, and took a brief look on your angle page: http://www.servocomm.freeserve.co.uk/Cpp/physical_quantity/angles.html I searched for the question: "Should angles be modulo? (IOW should 361 degrees ---> 1 degree etc.)" and was not really surprised to find it. I wanted to know how you treat this problem :). Here just my opinion: -we encountered here a problem with weights in calculations, meaning an angle was weighted via its a-priori error, which is an angle as well. Setting this angle to 360 degree was fatal. The programm crashed setting the error back to 0, what is not recommend in a division 1/error (hihi). It was fatal, but 361 degree would have been even worse, producing a result what is definitly not expected. -So we discussed if an angle bigger than 360 degree exists, and IMO - yes. Imagine you turn yourself 2 times, than you have a rotation of 720 degree and not 360 degree. I like more your idea with the modulo function, but keep in mind, that some applications use -180 to 180 degree and other 0 to 360 degree. And last, what is your opinion here: you might use clockwise-angles or counter-clockwise-angles. Is it necessary to distinguish these types? Thanks, regards, Patrick "Andy Little" <andy@servocomm.freeserve.co.uk> wrote in message news:<clapov$vpe$1@sea.gmane.org>... metaprogramming
book soon, at which point I can decide whether there are advantages. ---------------------
regards Andy Little
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