Convert implicitly decimal to double or double to decimal

Question

Double Precision is: 15-16 digits.

Decimal Precision is: 28-29 significant digits.

so we can convert decimal to double implicitly.But consider this code:

double x = 100.3;
decimal y = 10.2;
 x = y;
 y = x;

x=y and y=x both of them has compile time error.

Why we can not convert decimal to double or double to decimal implicitly?

Please read :double to decimal and decimal to double

Did you read the answer there? Did it address your question? — Martin Smith, Aug 11 '13 at 09:37
@ShahroozJefriㇱ Jon Skeet's answer is the answer to your question. The precision of decimals are much higher, but the range is much lower. This results in loss of data both ways. — Robert Rouhani, Aug 11 '13 at 09:40

Alex Siepman · Accepted Answer · 2013-08-11T09:49:16.023

2

The idea between these 2 types are completely different. See this blog of Eric Lippert.

Edit:

Quote of blog: "There cannot be an implicit conversion from double to decimal because of the range discrepancy; a huge number of doubles are larger than the largest possible decimal, and therefore an implicit conversion would either have to throw or silently lose perhaps an enormous quantity of magnitude, both of which are unacceptable. There could be an implicit conversion from decimal to double because that would only lose precision, not magnitude."

edited Aug 11 '13 at 09:49

answered Aug 11 '13 at 09:38

Alex Siepman

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Link only answers are discouraged. – It'sNotALie. Aug 11 '13 at 09:38
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@It'sNotALie. What else could I do in this situation? Is copying the content of the linked excellent blog better? – Alex Siepman Aug 11 '13 at 09:42
1

@AlexSiepman: You could quote the relevant part of the link if possible. That would also avoid the [Link rot](http://en.wikipedia.org/wiki/Linkrot) problem. – Tim Schmelter Aug 11 '13 at 09:44
@It'sNotALie. OK, that is a good option. – Alex Siepman Aug 11 '13 at 09:46

score 0 · Answer 2 · answered Aug 11 '13 at 09:36

Because although decimal's precision is higher, the range of doubles is bigger.

doubles go from -1.79769313486232E+308 to 1.79769313486232E+308. Meanwhile, decimals go from -79228162514264337593543950335to79228162514264337593543950335. There is a HUGE difference. However, you don't normally want to convert from decimal to double, as when you use decimal you normally don't want to lose precision (as they're normally used for banking, which needs to be exact).

Convert implicitly decimal to double or double to decimal

2 Answers2