Add spellcheck and word suggestion to the prediction service

third_party/prediction/suggest/core/layout/normal_distribution.h

Index: third_party/prediction/suggest/core/layout/normal_distribution.h
diff --git a/third_party/prediction/suggest/core/layout/normal_distribution.h b/third_party/prediction/suggest/core/layout/normal_distribution.h
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+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef LATINIME_NORMAL_DISTRIBUTION_H
+#define LATINIME_NORMAL_DISTRIBUTION_H
+
+#include <cmath>
+
+#include "third_party/prediction/defines.h"
+
+namespace latinime {
+
+// Normal distribution N(u, sigma^2).
+class NormalDistribution {
+ public:
+  NormalDistribution(const float u, const float sigma)
+      : mU(u),
+        mPreComputedNonExpPart(
+            1.0f / sqrtf(2.0f * M_PI_F * GeometryUtils::SQUARE_FLOAT(sigma))),
+        mPreComputedExponentPart(-1.0f /
+                                 (2.0f * GeometryUtils::SQUARE_FLOAT(sigma))) {}
+
+  float getProbabilityDensity(const float x) const {
+    const float shiftedX = x - mU;
+    return mPreComputedNonExpPart * expf(mPreComputedExponentPart *
+                                         GeometryUtils::SQUARE_FLOAT(shiftedX));
+  }
+
+ private:
+  DISALLOW_IMPLICIT_CONSTRUCTORS(NormalDistribution);
+
+  const float mU;                        // mean value
+  const float mPreComputedNonExpPart;    // = 1 / sqrt(2 * PI * sigma^2)
+  const float mPreComputedExponentPart;  // = -1 / (2 * sigma^2)
+};
+}  // namespace latinime
+#endif  // LATINIME_NORMAL_DISTRIBUTION_H