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// Copyright 2018 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef MEDIA_LEARNING_COMMON_VALUE_H_
#define MEDIA_LEARNING_COMMON_VALUE_H_
#include <cstdint>
#include <ostream>
#include <string>
#include <type_traits>
#include "base/component_export.h"
namespace media {
namespace learning {
// Lightweight, copyable value for features and labels.
// Strings are hashed into ints in an implementation-specific way, so don't
// count on ordering between them. See LearningTask for more info about nominal
// versus numerical values.
//
// For numeric values, ==, !=, > operators behave as one would expect.
//
// For strings, only == and != are guaranteed to be meaningful.
class COMPONENT_EXPORT(LEARNING_COMMON) Value {
public:
Value();
template <typename T>
explicit Value(const T& x) : value_(x) {
// We want to rule out mostly pointers, since they wouldn't make much sense.
// Note that the implicit cast would likely fail anyway.
static_assert(std::is_arithmetic<T>::value || std::is_enum<T>::value,
"media::learning::Value works only with arithmetic types");
}
explicit Value(const char* x);
explicit Value(const std::string& x);
explicit Value(bool x);
Value(const Value& other);
Value(Value&&) noexcept;
Value& operator=(const Value&);
Value& operator=(Value&&) noexcept;
bool operator==(const Value& rhs) const;
bool operator!=(const Value& rhs) const;
bool operator<(const Value& rhs) const;
bool operator>(const Value& rhs) const;
bool operator>=(const Value& rhs) const;
double value() const { return value_; }
private:
double value_ = 0;
friend COMPONENT_EXPORT(LEARNING_COMMON) std::ostream& operator<<(
std::ostream& out,
const Value& value);
// Copy and assign are fine.
};
// Just to make it clearer what type of value we mean in context.
using FeatureValue = Value;
using TargetValue = Value;
COMPONENT_EXPORT(LEARNING_COMMON)
std::ostream& operator<<(std::ostream& out, const Value& value);
} // namespace learning
} // namespace media
#endif // MEDIA_LEARNING_COMMON_VALUE_H_
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