140 lines
3.4 KiB
Markdown
140 lines
3.4 KiB
Markdown
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# Lexpr - universal expression evaluator
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This library can evaluate any types of expressions: math expression, logic expression, simple DSLs.
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## Installation
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`go get go.neonxp.dev/lexpr`
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## Usage
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Full example: [/example/main.go](/example/main.go)
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```go
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ctx := context.Background()
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l := lexpr.New(lexpr.WithDefaults())
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// Simple math
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result1 := <-l.Eval(ctx, `2 + 2 * 2`) // Output channel can return many results
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log.Println("Result 1:", result1.Value) // Output: 6
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// Helper for exact one result
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result2, err := l.OneResult(ctx, `len("test") + 10`)
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if err != nil {
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log.Fatal(err)
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}
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log.Println("Result 2:", result2) // Output: 14
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// Custom functions
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l.SetFunction("add", func(ts *lexpr.TokenStack) error {
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a, okA := ts.Pop().Number() // first func argument
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b, okB := ts.Pop().Number() // second func argument
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if !okA || !okB {
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return fmt.Errorf("Both args must be number")
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}
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ts.Push(lexpr.TokenFromInt(a + b))
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return nil
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})
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result3, err := l.OneResult(ctx, `add(12, 24) * 2`)
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if err != nil {
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log.Fatal(err)
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}
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log.Println("Result 3:", result3) // Output: 72
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// JSON extraction via dots and variables
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jsonString := `{
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"rootKey1": "value1",
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"rootKey2": {
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"childKey1": "value2",
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"childKey2": "value3"
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},
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"arrayKey": [
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"array value 1",
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"array value 2",
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"array value 3",
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"array value 4"
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]
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}`
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key1name := "rootKey1"
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l.SetVariable("jsonData", jsonString)
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l.SetVariable("key1name", key1name)
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result41, err := l.OneResult(ctx, `jsonData.key1name`)
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if err != nil {
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log.Fatal(err)
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}
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log.Println("Result 4-1:", result41) // Output: "value1"
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result42, err := l.OneResult(ctx, `jsonData.rootKey2.childKey2`)
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if err != nil {
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log.Fatal(err)
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}
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log.Println("Result 4-2:", result42) // Output: "value3"
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result43, err := l.OneResult(ctx, `jsonData.arrayKey.3`)
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if err != nil {
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log.Fatal(err)
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}
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log.Println("Result 4-3:", result43) // Output: "array value 4"
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// Logic expressions
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result51, err := l.OneResult(ctx, `jsonData.key1name == "value1"`)
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if err != nil {
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log.Fatal(err)
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}
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log.Println("Result 5-1:", result51) // Output: 1
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result52, err := l.OneResult(ctx, `10 >= 5 || 10 <= 5`)
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if err != nil {
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log.Fatal(err)
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}
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log.Println("Result 5-2:", result52) // Output: 0
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result53, err := l.OneResult(ctx, `10 >= 5 && 10 <= 5`)
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if err != nil {
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log.Fatal(err)
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}
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log.Println("Result 5-3:", result53) // Output: 0
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```
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## Default operators
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|Operator|Description|Example|
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|:------:|:---------:|:-----:|
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||JSON operators||
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|`.`|Extract field from json|`jsonData.key1.0.key2`|
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||Math operators||
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|`**`|Power number|`3 ** 3` = 27|
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|`*`|Multiple numbers|`2 * 4` = 8|
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|`/`|Divide number|`6 / 3` = 2|
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|`%`|Rem of division|`5 % 3` = 2|
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|`+`|Sum|`2 + 2` = 4|
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|`-`|Substract|`6 - 2` = 4|
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||Logic operators||
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|`!`|Logic not|`!1` = 0|
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|`>`|More|`3 > 2` = 1|
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|`>=`|More or equal|`3 >= 3` = 1|
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|`<`|Less|`3 < 2` = 0|
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|`<=`|Less or equal|`3 <= 3` = 1|
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|`==`|Equal|`1==1` = 1|
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|`!=`|Not equal|`1!=1` = 0|
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|`&&`|Logic and|`3 > 0 && 1 > 0` = 1|
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|`||`|Logic or|`1 > 0 || 1 == 1` = 1|
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## Default functions
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|Function|Description|Example|
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|:------:|:---------:|:-----:|
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|max|returns max of two values|`max(1,2)` = 2|
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|min|returns min of two values|`max(1,2)` = 1|
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|len|returns length of string|`len("test")` = 4|
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|atoi|converts string to number|`atoi("123")` = 123|
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|itoa|converts number to string|`itoa(123)` = "123"|
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## Contribution
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PRs are welcome.
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## Author
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Alexander Kiryukhin <i@neonxp.dev>
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## License
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