91 lines
2.6 KiB
Go
91 lines
2.6 KiB
Go
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// Copyright (c) 2016 Matthias Neugebauer
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//
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// Permission is hereby granted, free of charge, to any person obtaining a copy
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// of this software and associated documentation files (the "Software"), to deal
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// in the Software without restriction, including without limitation the rights
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// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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// copies of the Software, and to permit persons to whom the Software is
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// furnished to do so, subject to the following conditions:
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//
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// The above copyright notice and this permission notice shall be included in all
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// copies or substantial portions of the Software.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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// SOFTWARE.
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package reducer
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import (
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"errors"
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"math"
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)
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var (
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// ErrSliceEmpty indicates that the reduction failed because the slice was
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// empty.
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ErrSliceEmpty = errors.New("reducer: slice is empty")
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)
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// Reducer aggreate float64 slices.
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type Reducer interface {
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Reduce([]float64) (float64, error)
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}
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// Func is a reducers.
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type Func func([]float64) (float64, error)
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// Reduce implements the Reducer interface. It calls itself ensuring that the
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// slice is not empty.
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func (f Func) Reduce(data []float64) (float64, error) {
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if len(data) == 0 {
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return 0, ErrSliceEmpty
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}
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return f(data)
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}
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// Max returns an reducer that reduces the float64 slice to the maximum.
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func Max() Reducer {
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return Func(func(data []float64) (float64, error) {
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max := data[0]
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for i := 1; i < len(data); i++ {
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max = math.Max(max, data[i])
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}
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return max, nil
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})
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}
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// Min returns an reducer that reduces the float64 slice to the minimum.
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func Min() Reducer {
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return Func(func(data []float64) (float64, error) {
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min := data[0]
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for i := 1; i < len(data); i++ {
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min = math.Min(min, data[i])
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}
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return min, nil
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})
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}
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// Avg returns an reducer that reduces the float64 slice to the average.
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func Avg() Reducer {
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return Func(func(data []float64) (float64, error) {
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sum, _ := Sum().Reduce(data)
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return sum / float64(len(data)), nil
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})
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}
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// Sum returns an reducer that reduces the float64 slice to the sum.
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func Sum() Reducer {
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return Func(func(data []float64) (float64, error) {
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sum := data[0]
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for i := 1; i < len(data); i++ {
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sum += data[i]
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}
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return sum, nil
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})
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}
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