-
Notifications
You must be signed in to change notification settings - Fork 3
Percent
The percent datatype allows the expression and computation of percentages.
Convenience of data representation is the main reason for adding the percent datatype. Percent is a useful scaling factor for most numeric expressions, and also for the representation of relative values, such as graphical element sizes.
Or, stated quite simply: HTML has percent. It has been proven useful, and it has a humanly simple meaning that can be handy in our scripts.
Although we've added percent as a datatype, it's usefulness in mathematical expressions should be clearly understood: basically, it serves no improvement or extension from that of decimal values. In fact, percent internally is represented as a 64 bit floating point decimal number. 100% is simply 1.0.
What this means is that you should not expect fancy semantics when using percent as a term in math computations.
12.3 * 10% = 1.23but:
12.3 + 10% = 12.4and it is not the same as:
12.3 * 110% = 13.53It is good to keep that in mind, and don't get too excited that you've thought up a great new semantic for using percent. Members of the Rebol community have tried that and deemed it to be quite problematic.
So, what is the full definition of percent?
Well, we've kept it simple, but it is best described by what kinds of expressions you can write, and that is defined by a test script. The script is listed at the bottom of this page.
Ok, here's what to do if you find a bug or want to change the percent datatype.
- Talk it over with others in the Rebol community.
- If they agree with your opinion, then add one or more lines to the test file (kept in the R3-alpha world in the test-cases folder).
- Switch on the Batsignal.
This script defines the percent datatype. Each of these blocks evaluates TRUE.
[ 1.0 = 100%]
[ 1.05 = 105%]
[ 1.005 = 100.5%]
[ 0.5 = 50%]
[ 1.25 = 125%]
[-1.0 = -100%]
[-2.25 = -225%]
[1% == to percent! "1"]
[1% == to percent! "1%"]
[50% == to percent! "50"]
[100% == to percent! 1]
[100.5% == to percent! 1.005]
[120% == to percent! 1.2]
[100% == to percent! 1.0]
[50% == to percent! 0.5]
[100% == to percent! true]
[0% == to percent! false]
[1.0 == to decimal! 100%]
[1.25 == to decimal! 125%]
[0.5 == to decimal! 50%]
[1 == to integer! 100%]
[1 == to integer! 150%]
[0 == to integer! 1%]
[0 == to integer! 99%]
[true = (100% = 1)]
[true = (100% = 1.0)]
[false = ( 99% = 0)]
[true = ( 1% = 0.01)]
[1 = (1% * 100)] ; decimal result
[1.0 == (1% * 100.0)]
[1.5 == (3% * 50)] ; conversion to decimal
[1.5 == (3% * 50.0)]
[1 = (100 * 1%)]
[1.0 == (100.0 * 1%)]
[1.5 == (50 * 3%)] ; conversion to decimal
[1.5 == (50.0 * 3%)]
[1% == (1% * 100%)]
[50% == (100% * 50%)]
[1.0 == (50% / 50%)]
[20.0 == (10 / 50%)]
[0.05 = (50% / 10)]
[20.0 == (10.0 / 50%)]
[150% == (100% + 50%)]
[50% == (100% - 50%)]
[10.5 = ( 50% + 10)]
[10.6 = (50% + 10.1)]
[1.01 = (1 + 1%)]
[1.0 == (0 + 100%)]
[100.5 = (100 + 50%)]
[9.22337203685478E+18 = (9223372036854775807 + 100%)]
[1.0 == (1.01 - 1%)]
[-9.5 = (50% - 10)]
[ 9.5 = (10 - 50%)]
[$10.5 = (50% + $10)]
[$10.6 = (50% + $10.1)]
[$1.01 = ($1.00 + 1%)]
[$1.00 == ($1.01 - 1%)]
[$1.0 == ($0 + 100%)]
[$100.5 = ($100 + 50%)]
[-$9.5 = (50% - $10)]
[ $9.5 = ($10 - 50%)]
[255.255.255 = (255.255.255 * 100%)]
[255.255.255 = (255.255.255 * 150%)]
[150.150.150 = (100.100.100 * 150%)]
[101.101.101 = (100.100.100 + 150%)]
[127.127.127 = (255.255.255 * 50%)]
[255.255.255 = (100% * 255.255.255)]
[127.127.127 = (50% * 255.255.255)]
[127.127.127 = (255.255.255 / 200%)]
['a = pick [a b c] 100%]
['b = pick [a b c] 200%]
[none = pick [a b c] 99%]
[101x101 = (100x100 + 100%)]
[99x99 = (100x100 - 100%)]
[100x100 = (100x100 * 100%)]
[100x100 = (100x100 / 100%)]
[50x50 = (100x100 * 50%)]
[200x200 = (100x100 / 50%)]