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round.go
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round.go
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// Copyright (c) 2018 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
package linear
import (
"fmt"
"math"
"github.com/m3db/m3/src/query/block"
"github.com/m3db/m3/src/query/functions/lazy"
"github.com/m3db/m3/src/query/parser"
)
// RoundType rounds each datapoint in the series.
// Ties are resolved by rounding up. The optional to_nearest argument allows
// specifying the nearest multiple to which the timeseries values should be
// rounded (default=1). This variable may be a fraction.
// Special cases are: round(_, 0) = NaN
const RoundType = "round"
type roundOp struct {
toNearest float64
}
func parseArgs(args []interface{}) (float64, error) {
// NB: if no args passed; this should use default value of `1`.
if len(args) == 0 {
return 1, nil
}
if len(args) > 1 {
return 0, fmt.Errorf("invalid number of args for round: %d", len(args))
}
// Attempt to parse a single arg.
if nearest, ok := args[0].(float64); ok {
return nearest, nil
}
return 0, fmt.Errorf("unable to cast to to_nearest argument: %v", args[0])
}
func roundFn(roundTo float64) block.ValueTransform {
if roundTo == 0 {
return func(float64) float64 { return math.NaN() }
}
roundToInverse := 1.0 / roundTo
return func(v float64) float64 {
return math.Floor(v*roundToInverse+0.5) / roundToInverse
}
}
// NewRoundOp creates a new round op based on the type and arguments.
func NewRoundOp(args []interface{}) (parser.Params, error) {
toNearest, err := parseArgs(args)
if err != nil {
return nil, err
}
lazyOpts := block.NewLazyOptions().SetValueTransform(roundFn(toNearest))
return lazy.NewLazyOp(RoundType, lazyOpts)
}