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.. title:: clang-tidy - bugprone-fold-init-type
bugprone-fold-init-type
=======================
The check flags type mismatches in
`folds <https://en.wikipedia.org/wiki/Fold_(higher-order_function)>`_
like ``std::accumulate`` that might result in loss of precision.
``std::accumulate`` folds an input range into an initial value using the type of
the latter, with ``operator+`` by default. This can cause loss of precision
through:
- Truncation: The following code uses a floating point range and an int
initial value, so trucation wil happen at every application of ``operator+``
and the result will be `0`, which might not be what the user expected.
.. code-block:: c++
auto a = {0.5f, 0.5f, 0.5f, 0.5f};
return std::accumulate(std::begin(a), std::end(a), 0);
- Overflow: The following code also returns `0`.
.. code-block:: c++
auto a = {65536LL * 65536 * 65536};
return std::accumulate(std::begin(a), std::end(a), 0);
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