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digitalmars.D.learn - Why does D language do not support BigDecimal type?

reply BoQsc <vaidas.boqsc gmail.com> writes:
There is Money datatype that can be provided by using a third 
party package: https://code.dlang.org/packages/money

But that's only for money, what about math?
Why such fundamental as BigDecimal is still not included into the 
D language itself?
There is BigInt.

If it is unavoidable to use Floating point, how can I quickly and 
simply understand the rules of using float to make the least 
error, or should I just find a third party package for that as 
well?


There is an article on that, but it is not that straight forward:
https://dlang.org/articles/d-floating-point.html

Basically any thing that I find on Google, that include 
explaining floating point are badly written and hard to 
understand for the outsider lacking ability to understand 
advanced concepts.
Mar 11
next sibling parent Heromyth <bitworld qq.com> writes:
On Monday, 11 March 2019 at 15:23:34 UTC, BoQsc wrote:
 There is Money datatype that can be provided by using a third 
 party package: https://code.dlang.org/packages/money

 But that's only for money, what about math?
 Why such fundamental as BigDecimal is still not included into 
 the D language itself?
 There is BigInt.

 If it is unavoidable to use Floating point, how can I quickly 
 and simply understand the rules of using float to make the 
 least error, or should I just find a third party package for 
 that as well?


 There is an article on that, but it is not that straight 
 forward:
 https://dlang.org/articles/d-floating-point.html

 Basically any thing that I find on Google, that include 
 explaining floating point are badly written and hard to 
 understand for the outsider lacking ability to understand 
 advanced concepts.
We have being porting one from Java. See https://github.com/huntlabs/hunt/blob/master/source/hunt/math/BigDecimal.d. It's so sad that many methods are still commented out.
Mar 11
prev sibling next sibling parent reply Cym13 <cpicard purrfect.fr> writes:
On Monday, 11 March 2019 at 15:23:34 UTC, BoQsc wrote:
 There is Money datatype that can be provided by using a third 
 party package: https://code.dlang.org/packages/money

 But that's only for money, what about math?
 Why such fundamental as BigDecimal is still not included into 
 the D language itself?
 There is BigInt.

 If it is unavoidable to use Floating point, how can I quickly 
 and simply understand the rules of using float to make the 
 least error, or should I just find a third party package for 
 that as well?


 There is an article on that, but it is not that straight 
 forward:
 https://dlang.org/articles/d-floating-point.html

 Basically any thing that I find on Google, that include 
 explaining floating point are badly written and hard to 
 understand for the outsider lacking ability to understand 
 advanced concepts.
How much precision is enough in your use case? There's always a limit to how precise you need to be and how precise you can be, be it only because our memory is finite. I've never had a use case for BigDecimal myself, so forgive my ignorance, but wouldn't you get the exact same result by using BigInt? For example, if you need 20 decimals of precisions then any value times 10^20 will be a BigInt on which you can work, it's just a matter of displaying it correctly when outputing the result but it doesn't change the operations you have to perform. Is there anything that can't be done with BigInt really?
Mar 12
parent reply Boqsc <vaidas.boqsc gmail.com> writes:
On Tuesday, 12 March 2019 at 08:48:33 UTC, Cym13 wrote:
 On Monday, 11 March 2019 at 15:23:34 UTC, BoQsc wrote:
 There is Money datatype that can be provided by using a third 
 party package: https://code.dlang.org/packages/money

 But that's only for money, what about math?
 Why such fundamental as BigDecimal is still not included into 
 the D language itself?
 There is BigInt.

 If it is unavoidable to use Floating point, how can I quickly 
 and simply understand the rules of using float to make the 
 least error, or should I just find a third party package for 
 that as well?


 There is an article on that, but it is not that straight 
 forward:
 https://dlang.org/articles/d-floating-point.html

 Basically any thing that I find on Google, that include 
 explaining floating point are badly written and hard to 
 understand for the outsider lacking ability to understand 
 advanced concepts.
How much precision is enough in your use case? There's always a limit to how precise you need to be and how precise you can be, be it only because our memory is finite. I've never had a use case for BigDecimal myself, so forgive my ignorance, but wouldn't you get the exact same result by using BigInt? For example, if you need 20 decimals of precisions then any value times 10^20 will be a BigInt on which you can work, it's just a matter of displaying it correctly when outputing the result but it doesn't change the operations you have to perform. Is there anything that can't be done with BigInt really?
Please attach quick working examples for every sentence you write or it's just a waste of time. People want to see the results and direct actions first before anything else, it's more efficient communication. We are in the subforum of Dlang learn, after all. Do not write "For Example". I'm interested in writing a simple game prototype and I imagine that I would like to include some item parts in decimal. (100.00) To keep everything simple I would like to make my code as clean and simple as possible. Floating points seems to require additional arithmetics - rounding and are inprecise when comparing. I do not want to deal with it every time. But if there is any standard simple documentation that I could include into my own game documentation to avoid confusion and make everything consisten, I would like to know. For now it seems that the only way to make it all simple is to use some kind of library to handle decimals for me, as I can't find any concise references on how to correctly use and understand floating points.
Mar 12
next sibling parent spir <denis.spir gmail.com> writes:
On 12/03/2019 10:31, Boqsc via Digitalmars-d-learn wrote:
 Please attach quick working examples for every sentence you write or it's just
a 
 waste of time. People want to see the results and direct actions first before 
 anything else, it's more efficient communication. We are in the subforum of 
 Dlang learn, after all.
 
 Do not write "For Example".
Then you may help people helping you by giving examples of your own use cases, first.
 I'm interested in writing a simple game prototype and I imagine that I would 
 like to include some item parts in decimal. (100.00) To keep everything simple
I 
 would like to make my code as clean and simple as possible.
From this single example, you don't need "fractal" (decimal or binary) numbers at all, just plain ints. Look up "fixed point arithmetics" on wikipedia, the article is rather good. It's easy and clean in comparison, at least if you only need simple operations. (That's how, by the way, monetary/financial software is or at least used to be implemented.) diniz
Mar 12
prev sibling parent jmh530 <john.michael.hall gmail.com> writes:
On Tuesday, 12 March 2019 at 09:31:53 UTC, Boqsc wrote:
 [snip]

 Please attach quick working examples for every sentence you 
 write or it's just a waste of time. People want to see the 
 results and direct actions first before anything else, it's 
 more efficient communication. We are in the subforum of Dlang 
 learn, after all.
 [snip]
Honestly, I think this is a rather high burden to place on people. They are spending their valuable time to think about your question and answer it with what they think is the best response.
Mar 12
prev sibling next sibling parent Kagamin <spam here.lot> writes:
On Monday, 11 March 2019 at 15:23:34 UTC, BoQsc wrote:
 If it is unavoidable to use Floating point, how can I quickly 
 and simply understand the rules of using float to make the 
 least error, or should I just find a third party package for 
 that as well?
It's taught in a computational mathematics course. In short, you estimate how errors accumulate over operations in your algorithm, e.g. for a sum operation `x+y` of values with errors you have (x±dx)+(y±dy)±r, for which you calculate the range of values: minimum is x-dx+y-dy-r, maximum is x+dx+y+dy+r, so the error is dx+dy+r, where r is a rounding error, this error gets carried over to subsequent calculations. Similar for other operations. See for example https://en.wikipedia.org/wiki/Round-off_error#Accumulation_of_roundoff_error
Mar 12
prev sibling parent Seb <seb wilzba.ch> writes:
On Monday, 11 March 2019 at 15:23:34 UTC, BoQsc wrote:
 There is Money datatype that can be provided by using a third 
 party package: https://code.dlang.org/packages/money

 But that's only for money, what about math?
 Why such fundamental as BigDecimal is still not included into 
 the D language itself?
 There is BigInt.

 If it is unavoidable to use Floating point, how can I quickly 
 and simply understand the rules of using float to make the 
 least error, or should I just find a third party package for 
 that as well?


 There is an article on that, but it is not that straight 
 forward:
 https://dlang.org/articles/d-floating-point.html

 Basically any thing that I find on Google, that include 
 explaining floating point are badly written and hard to 
 understand for the outsider lacking ability to understand 
 advanced concepts.
I recommend that you learn floating point math as this will help you not only in programming in D, but in any other language. In any case, if you need super-high precision, you might want to give decimal [1] a try. [1] https://code.dlang.org/packages/decimal
Mar 12