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version 2.111.0

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Template std.sumtype.tryGet

Attempt to access a SumType's value.

template tryGet(T);

If the SumType does not contain a value of the specified type, an exception is thrown.

Contained Functions

NameDescription
tryGet The actual tryGet function.

Parameters

NameDescription
T the type of the value being accessed.

Example

Basic usage 

SumType!(string, double) example = "hello";

writeln(example.tryGet!string); // "hello"

double result = double.nan;
try
    result = example.tryGet!double;
catch (MatchException e)
    result = 0;

// Exception was thrown
writeln(result); // 0

Example

With type qualifiers 

import std.exception : assertThrown;

const(SumType!(string, double)) example = "const";

// Qualifier mismatch; throws exception
assertThrown!MatchException(example.tryGet!string);
// Qualifier matches; no exception
writeln(example.tryGet!(const(string))); // "const"
}

/// As a predicate
version (D_BetterC) {

Example

As a predicate 

import std.algorithm.iteration : map, sum;
import std.functional : pipe;
import std.exception : assertThrown;

alias Example = SumType!(string, double);

auto arr1 = [Example(0), Example(1), Example(2)];
auto arr2 = [Example("foo"), Example("bar"), Example("baz")];

alias trySum = pipe!(map!(tryGet!double), sum);

writeln(trySum(arr1)); // 0 + 1 + 2
assertThrown!MatchException(trySum(arr2));

Authors

Paul Backus

License

Boost License 1.0