Topic: Why std::optional has checked and unchecked access,
Author: Oleksandr Pikozh <o.pikozh@gmail.com>
Date: Tue, 16 Jan 2018 08:33:44 +0200
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In std::optional we have:
- operator* =E2=80=94 doesn't check whether an optional contains a value;
- method value =E2=80=94 throws std::bad_optional_access when an optional=
=20
doesn't contain a value.
In std::vector we have:
- operator[] =E2=80=94 doesn't check whether a vector contains specified in=
dex;
- method at =E2=80=94 throws std::out_of_range when a vector doesn't contai=
n=20
specified index.
In std::variant we have:
- ??? =E2=80=94 doesn't check whether a variant contains specified index/ty=
pe;
- method get =E2=80=94 throws std::bad_variant_access when a variant doesn'=
t=20
contain specified index/type.
Why we don't have any fast (unchecked) ways to access std::variant?=20
Assuming context when user has already checked for presence of required=20
item somehow and now needs the fastest access (i.e. he agrees to get UB=20
when absent).
--=20
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