expr

README

Expr Engine · 表达式引擎

基于 expr-lang/expr 的轻量级表达式引擎

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概述

Expr 引擎使用 expr-lang/expr 库，提供快速、类型安全的表达式求值。支持变量、函数和丰富的内置运算符，适用于业务表达式、模板引擎、数据筛选等场景。

引擎特性

特性	说明
底层库	github.com/expr-lang/expr v1.17.0
语言	Expr DSL
类型系统	Duck typing，编译时类型检查
环境快照	每次编译/执行时创建环境快照，保证一致性
线程安全	双锁模式（RWMutex + execMutex）
热更新	支持 StartWatch / StopWatch
类型常量	scriptEngine.ExprType

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安装

go get github.com/tx7do/go-scripts/expr

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快速开始

package main

import (
    "context"
    "fmt"
    "log"

    scriptEngine "github.com/tx7do/go-scripts"
    _ "github.com/tx7do/go-scripts/expr" // 注册 Expr 引擎
)

func main() {
    eng, _ := scriptEngine.NewScriptEngine(scriptEngine.ExprType)
    defer eng.Close()

    ctx := context.Background()
    eng.Init(ctx)

    // 注入变量
    _ = eng.RegisterGlobal("name", "world")
    _ = eng.RegisterGlobal("items", []int{1, 2, 3, 4, 5})

    // 注册函数
    _ = eng.RegisterFunction("double", func(x int) int { return x * 2 })

    // 求值表达式
    result, _ := eng.ExecuteString(ctx, "filter", `items | filter(# > 2) | map(double(#))`)
    fmt.Println(result) // [6, 8, 10]
}

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API 参考

方法	说明
Init(ctx)	初始化引擎环境
Close()	释放引擎资源
LoadString(ctx, name, code)	编译 Expr 表达式并加入队列
Execute(ctx)	顺序求值队列中所有表达式，返回最后一个结果
ExecuteString(ctx, name, code)	编译并立即求值内联 Expr 表达式
RegisterGlobal(name, value)	注册全局变量到表达式环境
RegisterFunction(name, fn)	注册 Go 函数到表达式环境
CallFunction(ctx, name, args...)	命令式调用已注册的宿主函数
RegisterModule(name, module)	注册命名空间模块
StartWatch(ctx, key)	启动表达式热更新监听
StopWatch(key)	停止热更新监听

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测试

cd expr && go test -v ./...

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相关文档

• 返回主文档
• Expr 官方文档
• Expr 语言参考

License

MIT License

Documentation

Overview

Package expr provides a script engine implementation using the Expr expression language (https://github.com/expr-lang/expr). Expr is a fast, type-safe expression evaluator that supports variables, functions, and a rich set of built-in operators.

Construction:

eng, _ := expr.New(ctx)
eng.Init(ctx)
eng.RegisterGlobal("name", "world")
result, _ := eng.ExecuteString(ctx, "greet", `"Hello " + name`)

The engine supports hot-reload via StartWatch/StopWatch when the bound Source implements the Watcher interface.

Index

• Variables

Variables

var (
	// ErrExprEngineNotInitialized is returned when an operation is invoked
	// before Init or after Close.
	ErrExprEngineNotInitialized = errors.New("expr engine not initialized")

	// ErrExprEngineAlreadyInitialized is returned when Init is called on an
	// already-initialized engine.
	ErrExprEngineAlreadyInitialized = errors.New("expr engine already initialized")

	// ErrExprCompileFailed is returned when compiling an expression fails.
	ErrExprCompileFailed = errors.New("expr compile failed")

	// ErrExprNoExpressionLoaded is returned when Execute is called but no
	// expression has been loaded.
	ErrExprNoExpressionLoaded = errors.New("expr no expression loaded")

	// ErrExprRunFailed is returned when evaluating an expression fails.
	ErrExprRunFailed = errors.New("expr run failed")

	// ErrExprFunctionNotFound is returned when CallFunction cannot find the
	// named function.
	ErrExprFunctionNotFound = errors.New("expr function not found")

	// ErrExprGlobalNotFound is returned when GetGlobal cannot find the named
	// variable.
	ErrExprGlobalNotFound = errors.New("expr global not found")
)

Sentinel errors returned by the Expr engine.