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/oleksandr/conditions"
)
func main() {
// Our condition to check
s := "($0 > 0.45) AND ($1 == `ON` OR $2 == \"ACTIVE\") AND $3 == false"
// 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{}{"$0": 0.12, "$1": "OFF", "$2": "ACTIVE", "$3": false}
r, err := conditions.Evaluate(expr, data)
if err != nil {
// ...
}
// r is false
fmt.Println("Evaluation result:", r)
}
Where do we use it?
Here is a diagram for a sample FBP flow (created using FlowMaker). You can see how we configure the ContextA process with a condition via IIP packet.
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
- func Evaluate(expr Expr, args map[string]interface{}) (bool, error)
- func FormatDuration(d time.Duration) string
- func Quote(s string) string
- func QuoteIdent(s string) string
- func Variables(expression Expr) []string
- func Walk(v Visitor, node Node)
- func WalkFunc(node Node, fn func(Node))
- type BinaryExpr
- type BooleanLiteral
- type DataType
- type DurationLiteral
- type Expr
- type Node
- type NumberLiteral
- type ParenExpr
- type Parser
- type SliceNumberLiteral
- type SliceStringLiteral
- type StringLiteral
- type TimeLiteral
- type Token
- type VarRef
- type Visitor
Constants ¶
Variables ¶
This section is empty.
Functions ¶
func FormatDuration ¶
FormatDuration formats a duration to a string.
func QuoteIdent ¶
QuoteIdent returns a quoted identifier if the identifier requires quoting. Otherwise returns the original string passed in.
Types ¶
type BinaryExpr ¶
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 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 ¶
DurationLiteral represents a duration literal.
func (*DurationLiteral) String ¶
func (l *DurationLiteral) String() string
String returns a string representation of the literal.
type Node ¶
type Node interface {
String() string
// contains filtered or unexported methods
}
Node represents a node in the conditions abstract syntax tree.
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.
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.
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
}
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 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 ¶
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 INTERSECTS // INTERSECTS (two sets has not empty intersect) HAS // HAS (element contains at set as left operand) LPAREN // ( RPAREN // ) )
func (Token) Precedence ¶
Precedence returns the operator precedence of the binary operator token.
Source Files