boostorg/optional
1
0
Fork 1
mirror of https://github.com/boostorg/optional.git synced 2025-07-29 20:17:21 +02:00
Code Issues Packages Projects Releases Wiki Activity

Added func value_or_eval()

Browse Source
This commit is contained in:
Andrzej Krzemienski
2014-06-18 15:01:52 +02:00
parent a158b85bd6
commit d70114b3dc
14 changed files with 536 additions and 50 deletions
Download Patch File Download Diff File Expand all files Collapse all files

11
doc/01_quick_start.qbk
View File

@ -48,7 +48,16 @@ This version throws an exception upon an attempt to access a non-existent contai
int k = convert(text).value_or(0);
This uses the `atoi`-like approach to conversions: if `text` does not represent an integral number just return `0`. Now, let's consider how function `convert` can be implemented.
This uses the `atoi`-like approach to conversions: if `text` does not represent an integral number just return `0`. Finally, you can provide a callback to be called when trying to access the contained value fails:
int l = convert(text).value_or_eval([]() -> int {
cout << "could not convert; using -1 instead" << endl;
return -1;
});
This will call the provided callback and return whatever the callback returns. The callback can have side effects: they will only be observed when the optional object does not contain a value.
Now, let's consider how function `convert` can be implemented.
boost::optionl<int> convert(const std::string& text)
{