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https://github.com/xaionaro-go/rpn

Reverse Polish Notation for Go (golang)
https://github.com/xaionaro-go/rpn

benchmark cc0 fast go golang jit performance reverse-polish-notation rpn

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Reverse Polish Notation for Go (golang)

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[![GoDoc](https://godoc.org/github.com/xaionaro-go/rpn?status.svg)](https://pkg.go.dev/github.com/xaionaro-go/rpn?tab=doc)
[![go report](https://goreportcard.com/badge/github.com/xaionaro-go/rpn)](https://goreportcard.com/report/github.com/xaionaro-go/rpn)
[![Build Status](https://travis-ci.org/xaionaro-go/rpn.svg?branch=master)](https://travis-ci.org/xaionaro-go/rpn)
[![Coverage Status](https://coveralls.io/repos/github/xaionaro-go/rpn/badge.svg?branch=master)](https://coveralls.io/github/xaionaro-go/rpn?branch=master)



CC0



To the extent possible under law,

Dmitrii Okunev

has waived all copyright and related or neighboring rights to
Reverse Polish Notation for Go.
This work is published from:

Ireland
.

# About

`github.com/xaionaro-go/rpn` is an implementation of [Reverse Polish Notation](https://en.wikipedia.org/wiki/Reverse_Polish_notation).
The implementation is focused on fast evaluation (but slow parsing).

# Quick start

```go
package main

import (
"fmt"

"github.com/xaionaro-go/rpn"
"github.com/xaionaro-go/rpn/types"
)

type variables struct {
X float64
}

func (r *variables) Resolve(sym string) (types.ValueLoader, error) {
switch sym {
case "x":
return types.FuncValue(func() float64 {
return r.X
}), nil
}
return nil, fmt.Errorf("symbol '%s' not found", sym)
}

func main() {
vars := &variables{}
expr, err := rpn.Parse("x 2 *", vars)
if err != nil {
panic(err)
}

vars.X = 1
_, _ = fmt.Println(expr.Eval())

vars.X = 3
_, _ = fmt.Println(expr.Eval())
}
```
The output is:
```
2
6
```

# Benchmark

There are 5 approaches implemented (`callslice`, `calltree`, `exprtree`, `compile` and `tokenslice`):

```
goos: linux
goarch: amd64
pkg: github.com/xaionaro-go/rpn/tests
BenchmarkExpr_Eval/cache_true/3_constant_values/callslice-4 1000000000 4.00 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/3_constant_values/calltree-4 1000000000 4.00 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/3_constant_values/exprtree-4 1000000000 3.72 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/3_constant_values/compile-4 1000000000 4.06 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/3_constant_values/tokenslice-4 1000000000 3.99 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/3_constant_values/default-4 1000000000 4.01 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/3_variables/default-4 1000000000 3.99 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/3_variables/callslice-4 1000000000 4.00 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/3_variables/calltree-4 1000000000 4.00 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/3_variables/exprtree-4 1000000000 3.73 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/3_variables/compile-4 1000000000 4.08 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/3_variables/tokenslice-4 1000000000 3.99 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/10_variables/callslice-4 1000000000 4.02 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/10_variables/calltree-4 1000000000 4.01 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/10_variables/exprtree-4 1000000000 3.72 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/10_variables/compile-4 1000000000 4.05 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/10_variables/tokenslice-4 1000000000 4.05 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/10_variables/default-4 1000000000 4.00 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/100_variables/callslice-4 1000000000 4.03 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/100_variables/calltree-4 1000000000 4.01 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/100_variables/exprtree-4 1000000000 3.73 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/100_variables/compile-4 1000000000 4.06 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/100_variables/tokenslice-4 1000000000 4.00 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/100_variables/default-4 1000000000 4.00 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/1000_variables/exprtree-4 1000000000 3.73 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/1000_variables/compile-4 1000000000 4.04 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/1000_variables/tokenslice-4 1000000000 4.00 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/1000_variables/default-4 1000000000 3.99 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/1000_variables/callslice-4 1000000000 4.00 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/1000_variables/calltree-4 1000000000 4.00 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/10000_variables/calltree-4 1000000000 4.06 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/10000_variables/exprtree-4 1000000000 3.72 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/10000_variables/compile-4 1000000000 4.05 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/10000_variables/tokenslice-4 1000000000 4.00 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/10000_variables/default-4 1000000000 3.99 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_true/10000_variables/callslice-4 1000000000 4.01 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/3_constant_values/callslice-4 579179106 10.4 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/3_constant_values/calltree-4 1000000000 5.51 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/3_constant_values/exprtree-4 376218780 15.9 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/3_constant_values/compile-4 451313248 13.3 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/3_constant_values/tokenslice-4 285631948 21.0 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/3_constant_values/default-4 1000000000 5.52 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/3_variables/callslice-4 331783568 18.1 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/3_variables/calltree-4 495298591 12.1 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/3_variables/exprtree-4 287268447 20.9 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/3_variables/compile-4 256272177 23.3 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/3_variables/tokenslice-4 229319173 26.4 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/3_variables/default-4 494261940 12.1 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/10_variables/callslice-4 100000000 52.9 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/10_variables/calltree-4 122009749 49.0 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/10_variables/exprtree-4 75151573 73.8 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/10_variables/compile-4 90459986 66.6 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/10_variables/tokenslice-4 69911527 85.7 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/10_variables/default-4 121929210 48.9 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/100_variables/calltree-4 10963188 548 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/100_variables/exprtree-4 7401158 808 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/100_variables/compile-4 8893951 678 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/100_variables/tokenslice-4 6937212 865 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/100_variables/default-4 12024320 491 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/100_variables/callslice-4 11103020 529 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/1000_variables/callslice-4 1000000 5396 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/1000_variables/calltree-4 885706 6453 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/1000_variables/exprtree-4 650157 9065 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/1000_variables/compile-4 876373 6829 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/1000_variables/tokenslice-4 694416 8591 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/1000_variables/default-4 1000000 5400 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/10000_variables/compile-4 84819 70461 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/10000_variables/tokenslice-4 68793 86768 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/10000_variables/default-4 104406 57272 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/10000_variables/callslice-4 104284 57153 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/10000_variables/calltree-4 77030 77918 ns/op 0 B/op 0 allocs/op
BenchmarkExpr_Eval/cache_false/10000_variables/exprtree-4 60081 99462 ns/op 0 B/op 0 allocs/op
PASS
ok github.com/xaionaro-go/rpn/tests 407.949s
```

The default approach for small expressions is `calltree`, and
for larger expression is `callslice`, so if you will import
`github.com/xaionaro-go/rpn` then if you will use them.