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36 lines
1.1 KiB
36 lines
1.1 KiB
2 years ago
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#pragma once
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#include <limits>
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namespace drake {
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/// Provides a "dummy" value for a ScalarType -- a value that is unlikely to be
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/// mistaken for a purposefully-computed value, useful for initializing a value
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/// before the true result is available.
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///
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/// Defaults to using std::numeric_limits::quiet_NaN when available; it is a
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/// compile-time error to call the unspecialized dummy_value::get() when
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/// quiet_NaN is unavailable.
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///
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/// See autodiff_overloads.h to use this with Eigen's AutoDiffScalar.
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template <typename T>
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struct dummy_value {
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static constexpr T get() {
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static_assert(std::numeric_limits<T>::has_quiet_NaN,
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"Custom scalar types should specialize this struct");
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return std::numeric_limits<T>::quiet_NaN();
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}
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};
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template <>
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struct dummy_value<int> {
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static constexpr int get() {
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// D is for "Dummy". We assume as least 32 bits (per cppguide) -- if `int`
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// is larger than 32 bits, this will leave some fraction of the bytes zero
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// instead of 0xDD, but that's okay.
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return 0xDDDDDDDD;
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}
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};
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} // namespace drake
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