Tri-Bar Calculator for Mac

From Tri-Bar Software:

Calculator is a novel calculator based upon 'fifth generation' and declarative programming languages. It is easy to use, yet extremely powerful and is ideal for experimenting, schools and for everyday calculations.

It is a powerful declarative calculator that is comparable in functionality to conventional hand-held scientific calculators, but is considerably easier to use (and is much more fun). It could easily be implemented as a hand-held device if any company was interested in improving calculator technology, though this demonstration runs on a computer.

The calculator is a simple and convincing demonstration of the simplicity and power of declarative user interfaces. In fact, it is so simple that many people have dismissed it as 'obvious' - which is an ironic response given the complexity manufacturers seem unable to avoid in conventional calculators. (Look at any scientific calculator: every button will have about four different meanings, depending on what shift keys have been pressed or what mode the calculator is in. A source of confusion and errors!)

Although this demonstration declarative user interface is a scientific calculator, there is no reason why the user interface should be restricted to arithmetic. Arithmetic is merely a language, so the simplicity and power of the approach is equally applicable to many other languages � from chess to aircraft flight management systems. Of course a declarative user interface is not necessarily the best solution for certain sorts of task, though the approach will certainly contribute to simplifying any user interface design.

The demonstration calculator's functions include the usual four arithmetic functions, as well as exponentiation, trigonometry, logarithms, and factorial. Many functions have options that support generalisations: multiplication, for example, can also be used for finding roots or prime factors; and division can find rational approximations (such as *=206921/65865). All functions have inverses, even including factorial (what is 40340 nearly the factorial of? � this sort of question is easy to solve). The calculator includes a database of numerical constants and formulas, such as the radius of the earth and all SI prefixes.