-
Notifications
You must be signed in to change notification settings - Fork 1
Lexicon
In the most basic terms, a dimension is a kind of thing that can be measured. For example, you can measure distance or time. There may be many ways to measure any one dimension, as well as many conventions for doing so, but it remains a single dimension. For example, I may measure distance in meters or in feet, using a yardstick or by calculating how long it takes light to travel from one end to the other, but it is still a distance.
In Fling, you cannot mix dimensions in an inconsistent way. For example, you would not be allowed to add seconds to meters - that would be nonsensical. However, within a dimension, there may exist many units of measurement, and these can be used interchangeably. For example, you can freely convert inches to meters since both of those units are in the distance dimension.
Units are specific quantities of a dimension used as references in measurements. For example, a meter (the unit) represents a specific amount of distance (the dimension). When we talk about converting measurements, we mean changing the units associated with a measurement. Doing so necessarily changes the value of the measurement. For example, if we have a measurement of 1 meter, changing the unit from meters to feet would also change the 1 to something closer to 3.
Remember that in Fling, units are associated with a dimension, and so are only interchangeable with units that share the same dimension.
A derived dimension is a dimension that represents two or more dimensions in one. Examples may work best here.
Velocity is defined as the distance traveled over some amount of time. This combines both distance and time dimensions. Units that work for velocity would not work for distance, and vice versa, because distance by itself is missing the time aspect that velocity contains.
Fling allows derived dimensions, but keeps the component dimensions relevant. This means that "meters per second" is a valid unit for velocity, as is "meters per minute" or "inches per hour". So long as the component parts of the unit are using the same dimensions, they are interchangeable.
A measurement represents a specific quantity of a dimension, expressed as a multiple of a unit in that dimension. For example, if we are measuring distance (the dimension), we may choose to use meters (the unit) and say that the distance we are talking about is 3.2 times the length of a meter.
In Fling, a measurement keeps track of the unit originally used to create it, but remember that this is just for convenience. You can easily change the unit used by a measurement to express the same measurement in a different way.
All measurements come with error bars, typically due to the limitations of the measurement instrument. For example, if I use a yard stick to measure the width of a human hair, I'll probably be off by a bit. Even if I tried to measure something more reasonable like my foot size, I won't be able to precisely determine the length because there are not enough lines on my yard stick. In this situation, I should not say that my foot is 12.000 inches long, but rather more like 12.0 inches long, where the digits after the tenths place are uncertain.
By default, measurements in Fling are created with infinite precision. To be more precise about your certainty, you should define the precision based on your measurement device. Doing so will tell Fling to carry that precision through different operations you might perform on the measurement (such as addition, multiplication, or conversion to other units).