conditions

package module
v0.2.1 Latest Latest
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 Go to latest Published: Aug 4, 2022 License: MIT Imports: 10 Imported by: 0

README

conditions

This package offers a parser of a simple conditions specification language (reduced set of arithmetic/logical operations). The package is mainly created for Flow-Based Programming components that require configuration to perform some operations on the data received from multiple input ports. But it can be used whereever you need externally define some logical conditions on the internal variables.

Additional credits for this package go to Handwritten Parsers & Lexers in Go by Ben Johnson on Gopher Academy blog and InfluxML package from InfluxDB repository.

Usage example

package main

import (
    "fmt"
    "strings"

    "github.com/zhouzhuojie/conditions"
)

func main() {
    // Our condition to check
    s := `({foo} > 0.45) AND ({bar} == "ON" OR {baz} IN ["ACTIVE", "CLEAR"])`

    // Parse the condition language and get expression
    p := conditions.NewParser(strings.NewReader(s))
    expr, err := p.Parse()
    if err != nil {
        // ...
    }

    // Evaluate expression passing data for $vars
    data := map[string]interface{}{"foo": 0.12, "bar": "OFF", "baz": "ACTIVE"}
    r, err := conditions.Evaluate(expr, data)
    if err != nil {
        // ...
    }

    // r is false
    fmt.Println("Evaluation result:", r)
}

Credit

Forked from https://github.com/oleksandr/conditions

The main differences are

  • Changed the syntax of variables from [foo] to {foo}.
  • Added CONTAINS.
  • Added float comparison with epsilon error torlerence.
  • Optimized long array IN/CONTAINS operator.
  • Removed redundant RWMutex for better performance.

Documentation

Overview

Package conditions package offers a parser of a simple conditions specification language (reduced set of arithmetic/logical operations). It was created for Flow-Based Programming components that require configuration to perform some operations on the data received from multiple input ports.

Index

Constants

View Source 
const (
	Unknown  = DataType("")
	Number   = DataType("number")
	Boolean  = DataType("boolean")
	String   = DataType("string")
	Time     = DataType("time")
	Duration = DataType("duration")
)

Variables

This section is empty.

Functions

func Evaluate 

func Evaluate(expr Expr, args map[string]interface{}) (bool, error)

Evaluate takes an expr and evaluates it using given args

func EvaluateWithArgResolver 

func EvaluateWithArgResolver(expr Expr, args ArgResolver) (bool, error)

EvaluateWithArgResolver takes an expr and evaluates it using given arg resolver

func FormatDuration 

func FormatDuration(d time.Duration) string

FormatDuration formats a duration to a string.

func Quote 

func Quote(s string) string

Quote returns a quoted string.

func QuoteIdent 

func QuoteIdent(s string) string

QuoteIdent returns a quoted identifier if the identifier requires quoting. Otherwise returns the original string passed in.

func SetDefaultEpsilon 

func SetDefaultEpsilon(ep float64)

SetDefaultEpsilon sets the defaultEpsilon

func Variables 

func Variables(expression Expr) []string

Variables ...

func Walk 

func Walk(v Visitor, node Node)

Walk traverses a node hierarchy in depth-first order.

func WalkFunc 

func WalkFunc(node Node, fn func(Node))

WalkFunc traverses a node hierarchy in depth-first order.

Types

type ArgResolver 

type ArgResolver interface {
	Resolve(key string) (interface{}, error)
}

func NewMapArgResolver 

func NewMapArgResolver(args map[string]interface{}) ArgResolver

type BinaryExpr 

type BinaryExpr struct {
	Op  Token
	LHS Expr
	RHS Expr
}

BinaryExpr represents an operation between two expressions.

func (*BinaryExpr) Args 

func (e *BinaryExpr) Args() []string

func (*BinaryExpr) String 

func (e *BinaryExpr) String() string

String returns a string representation of the binary expression.

type BooleanLiteral 

type BooleanLiteral struct {
	Val bool
}

BooleanLiteral represents a boolean literal.

func (*BooleanLiteral) Args 

func (l *BooleanLiteral) Args() []string

func (*BooleanLiteral) String 

func (l *BooleanLiteral) String() string

String returns a string representation of the literal.

type Collection added in v0.2.0 

type Collection interface {
	String() string
	Count() int
}

func NewCollection added in v0.2.0 

func NewCollection(items []interface{}) (Collection, error)

func NewMapNumberCollection 

func NewMapNumberCollection(items []interface{}) Collection

func NewMapNumberCollectionFromMap added in v0.2.0 

func NewMapNumberCollectionFromMap(items map[float64]bool) Collection

func NewMapStringCollection added in v0.1.4 

func NewMapStringCollection(items []interface{}) Collection

func TryNewCollection added in v0.2.0 

func TryNewCollection(items []interface{}) Collection

type DataType 

type DataType string

DataType represents the primitive data types available in InfluxQL.

func InspectDataType 

func InspectDataType(v interface{}) DataType

InspectDataType returns the data type of a given value.

type DurationLiteral 

type DurationLiteral struct {
	Val time.Duration
}

DurationLiteral represents a duration literal.

func (*DurationLiteral) String 

func (l *DurationLiteral) String() string

String returns a string representation of the literal.

type Expr 

type Expr interface {
	Node

	Args() []string
	// contains filtered or unexported methods
}

Expr represents an expression that can be evaluated to a value.

type MapArgResolver 

type MapArgResolver struct {
	// contains filtered or unexported fields
}

func (*MapArgResolver) Resolve 

func (r *MapArgResolver) Resolve(key string) (interface{}, error)

type MapNumberCollection 

type MapNumberCollection struct {
	// contains filtered or unexported fields
}

func (*MapNumberCollection) Count added in v0.2.0 

func (c *MapNumberCollection) Count() int

func (*MapNumberCollection) Has 

func (c *MapNumberCollection) Has(number float64) bool

func (*MapNumberCollection) String 

func (c *MapNumberCollection) String() string

type MapStringCollection added in v0.1.4 

type MapStringCollection struct {
	// contains filtered or unexported fields
}

func (*MapStringCollection) Count added in v0.2.0 

func (c *MapStringCollection) Count() int

func (*MapStringCollection) Has added in v0.1.4 

func (c *MapStringCollection) Has(val string) bool

func (*MapStringCollection) String added in v0.1.4 

func (c *MapStringCollection) String() string

type Node 

type Node interface {
	String() string
	// contains filtered or unexported methods
}

Node represents a node in the conditions abstract syntax tree.

type NumberCollection 

type NumberCollection interface {
	Has(number float64) bool
	String() string
}

type NumberCollectionLiteral 

type NumberCollectionLiteral struct {
	Val NumberCollection
}

func (*NumberCollectionLiteral) Args 

func (l *NumberCollectionLiteral) Args() []string

func (*NumberCollectionLiteral) String 

func (l *NumberCollectionLiteral) String() string

type NumberLiteral 

type NumberLiteral struct {
	Val float64
}

NumberLiteral represents a numeric literal.

func (*NumberLiteral) Args 

func (n *NumberLiteral) Args() []string

func (*NumberLiteral) String 

func (l *NumberLiteral) String() string

String returns a string representation of the literal.

type ParenExpr 

type ParenExpr struct {
	Expr Expr
}

ParenExpr represents a parenthesized expression.

func (*ParenExpr) Args 

func (p *ParenExpr) Args() []string

func (*ParenExpr) String 

func (e *ParenExpr) String() string

String returns a string representation of the parenthesized expression.

type Parser 

type Parser struct {
	// contains filtered or unexported fields
}

Parser encapsulates the scanner and responsible for returning AST composed from statements read from a given reader.

func NewParser 

func NewParser(r io.Reader) *Parser

NewParser returns a new instance of Parser.

func (*Parser) Parse 

func (p *Parser) Parse() (Expr, error)

Parse starts scanning & parsing process (main entry point). It returns an expression (AST) which you can use for the final evaluation of the conditions/statements

type SliceNumberLiteral 

type SliceNumberLiteral struct {
	Val []float64
}

func (*SliceNumberLiteral) Args 

func (l *SliceNumberLiteral) Args() []string

func (*SliceNumberLiteral) String 

func (l *SliceNumberLiteral) String() string

String returns a string representation of the literal.

type SliceStringLiteral 

type SliceStringLiteral struct {
	Val []string
	// contains filtered or unexported fields
}

func NewSliceStringLiteral 

func NewSliceStringLiteral(val []string) *SliceStringLiteral

func (*SliceStringLiteral) Args 

func (l *SliceStringLiteral) Args() []string

func (*SliceStringLiteral) String 

func (l *SliceStringLiteral) String() string

String returns a string representation of the literal.

type StringCollection added in v0.1.4 

type StringCollection interface {
	Has(val string) bool
	String() string
}

type StringCollectionLiteral added in v0.1.4 

type StringCollectionLiteral struct {
	Val StringCollection
}

func (*StringCollectionLiteral) Args added in v0.1.4 

func (l *StringCollectionLiteral) Args() []string

func (*StringCollectionLiteral) String added in v0.1.4 

func (l *StringCollectionLiteral) String() string

type StringLiteral 

type StringLiteral struct {
	Val string
}

StringLiteral represents a string literal.

func (*StringLiteral) Args 

func (l *StringLiteral) Args() []string

func (*StringLiteral) String 

func (l *StringLiteral) String() string

String returns a string representation of the literal.

type TimeLiteral 

type TimeLiteral struct {
	Val time.Time
}

TimeLiteral represents a point-in-time literal.

func (*TimeLiteral) String 

func (l *TimeLiteral) String() string

String returns a string representation of the literal.

type Token 

type Token int

Token represents a lexical token. 

const (
	// ILLEGAL token represent illegal token found in the statement
	ILLEGAL Token = iota
	// EOF token represents end of statement
	EOF

	IDENT  // Variable references $0, $5, etc
	NUMBER // 12345.67
	STRING // "abc"
	ARRAY  // array of values (string or number) ["a","b","c"]  [342,4325,6,4]
	TRUE   // true
	FALSE  // false

	AND         // AND
	OR          // OR
	EQ          // =
	NEQ         // !=
	LT          // <
	LTE         // <=
	GT          // >
	GTE         // >=
	NAND        // NAND
	XOR         // XOR
	EREG        // =~
	NEREG       // !~
	IN          // IN
	NOTIN       // NOT IN
	CONTAINS    // CONTAINS
	NOTCONTAINS // NOT CONTAINS

	LPAREN // (
	RPAREN // )
)

func (Token) Precedence 

func (tok Token) Precedence() int

Precedence returns the operator precedence of the binary operator token.

func (Token) String 

func (tok Token) String() string

String returns the string representation of the token.

type VarRef 

type VarRef struct {
	Val string
}

VarRef represents a reference to a variable.

func (*VarRef) Args 

func (r *VarRef) Args() []string

func (*VarRef) String 

func (r *VarRef) String() string

String returns a string representation of the variable reference.

type Visitor 

type Visitor interface {
	Visit(Node) Visitor
}

Visitor can be called by Walk to traverse an AST hierarchy. The Visit() function is called once per node.

Source Files

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