expectations 0.2.0

Error handling that bundles exceptions with return values


To use this package, put the following dependency into your project's dependencies section:

dub.json
dub.sdl

expectations

Error handling that bundles exceptions with return values.

Features

  • Expected values can be treated like return codes or exceptions:
    • Use hasValue to check for success or failure explicitly.
    • Use value directly to assume success and throw in case of failure.
  • Error handling is deferred until the value is actually needed.
  • Functions that return Expected values can be composed easily using andThen and map.
  • Usable in @safe and nothrow code.

Documentation

View online on Github Pages.

expectations uses adrdox to generate its documentation. To build your own copy, run the following command from the root of the sumtype repository:

path/to/adrdox/doc2 --genSearchIndex --genSource -o generated-docs src


Example

import std.math: approxEqual;
import std.exception: assertThrown;
import std.algorithm: equal;

Expected!double relative(double a, double b)
{
    if (a == 0) {
        return unexpected!double(
            new Exception("Division by zero")
        );
    } else {
        return expected((b - a)/a);
    }
}

assert(relative(2, 3).hasValue);
assert(relative(2, 3).value.approxEqual(0.5));

assert(!relative(0, 1).hasValue);
assertThrown(relative(0, 1).value);
assert(relative(0, 1).exception.msg.equal("Division by zero"));

Installation

If you're using dub, add the expectations package to your project as a dependency.

Otherwise, you will need to add both expectations.d and its dependency sumtype.d (from the sumtype package) to your source directory.

Authors:
  • Paul Backus
Dependencies:
sumtype
Versions:
0.2.0 2018-Sep-04
0.1.0 2018-Sep-02
~master 2018-Sep-08
Show all 3 versions
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Short URL:
expectations.dub.pm