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Document Approx's UDL support

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Martin Hořeňovský 2018-07-15 17:38:57 +02:00
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docs/assertions.md
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@ -61,11 +61,24 @@ Catch provides a way to perform tolerant comparisons of floating point values th
REQUIRE( performComputation() == Approx( 2.1 ) );
```
This way `Approx` is constructed with reasonable defaults, covering most simple cases of rounding errors. If these are insufficient, each `Approx` instance has 3 tuning knobs, that can be used to customize it for your computation.
Catch also provides a UDL for `Approx`; `_a`. It resides in
the `Catch::literals` namespace and can be used like so:
```cpp
using namespace Catch::literals;
REQUIRE( performComputation() == 2.1_a );
```
* __epsilon__ - epsilon serves to set the percentage by which a result can differ from `Approx`'s value before it is rejected. By default set to `std::numeric_limits<float>::epsilon()*100`.
* __margin__ - margin serves to set the the absolute value by which a result can differ from `Approx`'s value before it is rejected. By default set to `0.0`.
* __scale__ - scale is used to change the magnitude of `Approx` for relative check. By default set to `0.0`.
`Approx` is constructed with defaults that should cover most simple cases.
For the more complex cases, `Approx` provides 3 customization points:
* __epsilon__ - epsilon serves to set the percentage by which a result
can differ from `Approx`'s value before it is rejected.
_By default set to `std::numeric_limits<float>::epsilon()*100`._
* __margin__ - margin serves to set the the absolute value by which
a result can differ from `Approx`'s value before it is rejected.
_By default set to `0.0`._
* __scale__ - scale is used to change the magnitude of `Approx` for relative check.
_By default set to `0.0`._
#### epsilon example
```cpp