Comments (2)
Yes, great point! Documentation is one area that can always be improved.
In lieu of updating the docs, the short answer is that the tolerance provides the acceptable range in which we can consider the result correct. The lower the tolerance, the more accurate the result, however it also means it may be a slower calculation. We're effectively allowing us to configure how deep into the "series" that we need to go before achieving an acceptable result.
Of course the reverse of this, the higher the tolerance, the more inexact the result is going to potentially be. That said, for some simple applications, this may be fine.
So in terms of guarantees, tolerance is kind of like specifying that the result is going to be within 0 <= x <= tolerance of the final answer OR has reached the end of the series due to not being able to represent a more granular result within Decimal (yet!!!). Because of the latter (i.e. end of the series), it's difficult to make a strong guarantee right now, but hopefully it helps.
from rust-decimal.
Thanks for the answer.
So in terms of guarantees, tolerance is kind of like specifying that the result is going to be within 0 <= x <= tolerance of the final answer OR has reached the end of the series due to not being able to represent a more granular result within Decimal (yet!!!). Because of the latter (i.e. end of the series), it's difficult to make a strong guarantee right now, but hopefully it helps.
I understand the role of tolerance and think it is a very intuitive API.
But, as a (maybe not so well-informed) user, I expect that a given tolerance specified in Decimal
will translate to an actual error guarantee (which is not the case and it is very hard to do).
Proposal
If the idea is that tolerance
is really just a hint, and no formal guarantee will be given, I suggest renaming the input tolerance
to tolerance_hint
and adding to the documentation that no guarantee is given in the result of the computation.
Alternative 1
Change the return type to signal that the result is not within the tolerance level specified.
From
fn checked_exp_with_tolerance(&self, tolerance: Decimal) -> Option<Decimal>
to
fn checked_exp_with_tolerance(&self, tolerance: Decimal) -> Result<Decimal, ToleranceError>
where ToleranceError
has variants: Overflow
and OutOfRange
(or similar).
Alternative 2
A different approach would be to accept a tolerance_level: usize
parameter (renamed cutoff
or something else) that specifies the number of terms in the expansion used in the computation.
But honestly, I do not know how useful this would be, and accepting any usize is also a problem because the terms of the series are finite, so one can not use the same approach to deal with any usize as a cutoff limit.
from rust-decimal.
Related Issues (20)
- `serde-arbitrary-precision` without `serde-float` HOT 7
- `is_integer` has BUG HOT 1
- How to serialize Decimal and still keep the results in order (bitwise comparison) HOT 3
- Serialization V2 - brainstorming HOT 1
- feature request: JSON schema support via https://github.com/GREsau/schemars HOT 1
- Feature Request: Support wasm_bindgen for Decimal
- rlp (de)serialization? HOT 2
- Rust Decimal: Request for additional repository Owner/Collaborator(s) HOT 1
- Rescaling a value with significant scale 28 to scale 29 creates a value with scale 29 and overflows on subtraction HOT 1
- Support for mongo HOT 2
- To f64 losing accuracy for `100000.000000000000000000` HOT 1
- Scaling string representation differs from dividing by 10^x HOT 4
- too rubbish to called rust decimal HOT 3
- checked_powd takes exponentially long time to complete HOT 6
- Scale changes unexpectedly after operations HOT 3
- 1.34.0 breaks with cyclic dependency when installed with "macros" feature HOT 4
- Deserializing `Decimal`s from Postgres using the `db-postgres` feature can lead to invalid `Decimal` instances HOT 4
- Bug: not 128bit aligned with `repr-c` feature HOT 3
- Return error rather than panic in `FromSql` when overflow HOT 1
- Bug: Decimal::from_sql incorrectly transforms Postgres NaN to 0 HOT 1
Recommend Projects
-
React
A declarative, efficient, and flexible JavaScript library for building user interfaces.
-
Vue.js
🖖 Vue.js is a progressive, incrementally-adoptable JavaScript framework for building UI on the web.
-
Typescript
TypeScript is a superset of JavaScript that compiles to clean JavaScript output.
-
TensorFlow
An Open Source Machine Learning Framework for Everyone
-
Django
The Web framework for perfectionists with deadlines.
-
Laravel
A PHP framework for web artisans
-
D3
Bring data to life with SVG, Canvas and HTML. 📊📈🎉
-
Recommend Topics
-
javascript
JavaScript (JS) is a lightweight interpreted programming language with first-class functions.
-
web
Some thing interesting about web. New door for the world.
-
server
A server is a program made to process requests and deliver data to clients.
-
Machine learning
Machine learning is a way of modeling and interpreting data that allows a piece of software to respond intelligently.
-
Visualization
Some thing interesting about visualization, use data art
-
Game
Some thing interesting about game, make everyone happy.
Recommend Org
-
Facebook
We are working to build community through open source technology. NB: members must have two-factor auth.
-
Microsoft
Open source projects and samples from Microsoft.
-
Google
Google ❤️ Open Source for everyone.
-
Alibaba
Alibaba Open Source for everyone
-
D3
Data-Driven Documents codes.
-
Tencent
China tencent open source team.
from rust-decimal.