C# Check range of value with valid increments

Question

Seems simple, but can't find an elegant way... I want to check if a value is within a certain range, but also is using a valid increment/resolution. Say my range is 0.1 to 99.9, with a resolution of .1. Valid values would be 1.1 and 1.2, but 1.15 is not valid. How would I check that?

What is the type of your value? Decimal? float? – RB. Sep 04 '12 at 15:19 — RB., Sep 04 '12 at 15:19

D'Arcy Rittich · Accepted Answer · 2012-09-04T15:34:26.677

1

You can use the % operator:

float i = 1.15;
Console.WriteLine((decimal)i % .1M == 0);

Output: false

float i = 1.1;
Console.WriteLine((decimal)i % .1M == 0);

Output: true

edited Sep 04 '12 at 15:34

answered Sep 04 '12 at 15:21

D'Arcy Rittich

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What if there are multiple decimals? This won't work in general. – Tudor Sep 04 '12 at 15:24
@Tim Croydon: It only works to test if the number has more than one decimal, but what if all values in the domain (both correct and incorrect) have at least 2 decimals? – Tudor Sep 04 '12 at 15:26
@Tudor If two decimal were valid (not in this case according to OP), you would use `.01` instead of `.1`. – D'Arcy Rittich Sep 04 '12 at 15:30
@RedFilter: I suppose that's just an example and the OP can have any decimal "resolution". – Tudor Sep 04 '12 at 15:32
Updated for `float` data type specified in subsequent comment. – D'Arcy Rittich Sep 04 '12 at 15:35
Thanks guys. This did the trick, although I had to cast my double as decimal. Doing that operation on doubles doesn't work. But no big deal for me! – user1646235 Sep 04 '12 at 15:41

score 0 · Answer 2 · answered Sep 04 '12 at 15:23

0

Try something like this (for 0.1 resolution):

(x * 10) % 1 == 0

answered Sep 04 '12 at 15:23

Tim Croydon

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score 0 · Answer 3 · answered Sep 04 '12 at 15:25

Please try:

        double a = 0.1;
        double b = 99.9;
        double x = 1.5;
        double range = 0.5;
        double epsilon = 0.000001;

        bool isRange = (x >= a) && (x <= b) && (Math.Abs((x - a)%range) < epsilon);

Here epsilon is some very small 'mistake' value

Andrei · Answer 4 · 2012-09-04T15:32:46.020

You are dealing with arithmetic progression. In your example a[1] = 0.1, d = 0.1, a[999] = 99.9. If your number x is the nth member of the progression then the following holds:

n = (x - a[1])/d + 1

So you have to check whether

(x - a[1])/d

is a nonegative integer. For example:

(1.1 - 0.1)/0.1 = 10

therefore 1.1 is a member of progression. However:

(1.15 - 0.1)/0.1 = 10.5

therefore 1.15 is not a member of progression.

score 0 · Answer 5 · answered Sep 04 '12 at 15:31

0

Try with this code

decimal yourDecimal = ;

if( yourDecimal % .1M == 0 )
{
    ......
}

answered Sep 04 '12 at 15:31

Aghilas Yakoub

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score 0 · Answer 6 · edited May 23 '17 at 11:56

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Consider using Math.Round to force it to the precision you want. What's the difference between 1.999 and 1.2 in your application? (See also this SO question)

edited May 23 '17 at 11:56

Community

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answered Sep 04 '12 at 15:31

Dan Pichelman

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C# Check range of value with valid increments

6 Answers6