What's the second minimum value that a decimal can represent? That is the value which is larger than Decimal.MinValue and smaller than any other values that a decimal can represent. How can I obtain this value in C#? Thanks!
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Jon
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xiagao1982
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The second-minimum value is Decimal.MinValue + 1.
This can be inferred from the documentation for decimal:
A decimal number is a floating-point value that consists of a sign, a numeric value where each digit in the value ranges from 0 to 9, and a scaling factor that indicates the position of a floating decimal point that separates the integral and fractional parts of the numeric value.
The binary representation of a Decimal value consists of a 1-bit sign, a 96-bit integer number, and a scaling factor used to divide the 96-bit integer and specify what portion of it is a decimal fraction. The scaling factor is implicitly the number 10, raised to an exponent ranging from 0 to 28. Therefore, the binary representation of a Decimal value is of the form, ((-2^96 to 2^96) / 10^(0 to 28)), where -2^96-1 is equal to MinValue, and 2^96-1 is equal to MaxValue.
From the above we can infer that on the extreme edges of the legal value range, the scaling factor is 1 (10 to the power 0) and therefore that's the smallest quantum when a decimal value is modified.
Jon
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According to MSDN, a decimal is represented like ((-2^96 to 2^96) / 10^(0 to 28)), where -2^96-1 is equal to MinValue, and 2^96-1 is equal to MaxValue, so the smallest difference between two decimals is 1/10^28.
That difference is only possible between small decimals though. Generally, as a decimal becomes larger (no matter the sign), you lose decimal points, until there are none left.
UPDATE: As also pointed out in the comments, you can't actually change decimal.MinValue by adding the smallest decimal value (as above). Decimal has 1 bit for the sign, 96 bit for a number and a scaling factor (10^x) by which the number is divided.
In order to get to such a large negative number, the exponent portion of the scaling factor must be set to 0 (-> 10^0 == 1), because setting it to anything higher would cause the number to be divided by that and thus it would get smaller.
That means, for such a number, the smallest difference would be 1/10^0, or 1.
So you are looking for this:
decimal.MinValue + 1m;
Botz3000
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+1, I *think* this is what the OP is after. Possibly the answer would be `Decimal.MinValue + 0.000...1`. – George Duckett Jun 28 '12 at 09:44
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@Botz3000, @George: But `(Decimal.MinValue + 0.000...1) == Decimal.MinValue`. – LukeH Jun 28 '12 at 09:46
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1-1: This is incorrect. The scaling factor represents the portion of the 96 bits that is a decimal fraction. You can trivially confirm this by checking what `Decimal.MinValue + 0.000001m` is. – Jon Jun 28 '12 at 09:47
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@LukeH: Surely there is some number that when added to `Decimal.MinValue` such that `Decimal.MinValue + x > Decimal.MinValue` where `x < 1`. – George Duckett Jun 28 '12 at 09:48
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@GeorgeDuckett: "Surely" why? Any hard facts? – Jon Jun 28 '12 at 09:51
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@Jon, see my comment on the other answer. I'm guessing that my understanding of decimal is wrong. – George Duckett Jun 28 '12 at 09:51
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@George: Well, you could set `x` to `0.49999999999999999999999999995` in your source code if you like, but `Decimal.MinValue + x` would still be `-79,228,162,514,264,337,593,543,950,334`. – LukeH Jun 28 '12 at 09:53
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@GeorgeDuckett: Please remove your upvote too, as this answer is factually wrong. – Jon Jun 28 '12 at 09:53
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@Jon: I tried to earlier, but no edit so couldn't. Have now removed. – George Duckett Jun 28 '12 at 09:54
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@Jon Got it wrong. I edited my answer and added some explanation of the reason. – Botz3000 Jun 28 '12 at 10:05
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@Botz3000: Downvote removed, but please edit further because the very first line of the current version is still wrong. – Jon Jun 28 '12 at 10:14
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http://msdn.microsoft.com/en-us/library/system.decimal.minvalue.aspx
Decimal.MinValue + 1
So: -79,228,162,514,264,337,593,543,950,334.
t3hn00b
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Since it's decimal why add 1.0, why not 0.00000....1 (maybe what asker is asking) – George Duckett Jun 28 '12 at 09:43
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@George: Because the `Decimal` type can't represent any intermediate values between `-79,228,162,514,264,337,593,543,950,335` and `-79,228,162,514,264,337,593,543,950,334`. The smallest discrete step is 1. – LukeH Jun 28 '12 at 09:49
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I'm a bit confused now, as i thought the point of decimal (as opposed to float etc.) is that the difference in values it can represent is fixed. – George Duckett Jun 28 '12 at 09:50