Information about RationalCalc, the length calculator for Android.

RationalCalc and precision

From the comments in the Android Market, it has become clear that there is one fundamental point that is causing frustration with people getting started with RationalCalc.  The problem is that they are downloading the app, trying out a couple calculations and getting what they see as incorrect answers.

For instance, @Yeti writes, "13" = 1 1/16' ? News to me. Uninstalled." and @Roy says, "1 inch does not equal 1/16 feet, delete."

The confusion is that RationalCalc always works at a specific precision.  While the internal calculation is stored as a set of rational numbers making RationalCalc's results extremely accurate, the displayed answer is always rounded to the "Display Unit" and "Precision".  That means that you must consider the environment that you are working in, determine the degree of accuracy that you need and set the precision setting appropriately.

For instance, a carpenter in the United States might use the following settings:

Display Unit: FT/IN
Precision: 1/16 or 1/32

A machinist who was using a tool that had 10 notches between each MM might use the following settings:

Display Unit: MM
Precision: 1/10

The default settings on first install are:

Display Unit:  FT
Precision: 1/16
Rounding: Up

It is vital that you change these default settings to meet the needs of your specific task.

RationalCalc is entirely based around smoothing the difference between Metric and Imperial units and automatically rounding to a certain precision.  So, when someone enters 13", they might expect to see 13" or 1 and 1/12 feet.  When RationalCalc is set to Feet with a precision of 1/16, it sees 13 inches as 1 foot and a 16th of an inch because it has rounded the remaining inch to the nearest 16th of a foot.

Should I set the out of the box settings to FT/IN with a precision of 1/16?  Would it be more clear if you had to select your settings when RationalCalc was first installed?  Would it help if the current settings were displayed on the main screen all of the time?

Any feedback would be great!

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