Documentation
¶
Overview ¶
Package parser contains the EQL parser.
Lexer ¶
Lex() is a lexer function to convert a given search query into a list of tokens.
Based on a talk by Rob Pike: Lexical Scanning in Go
https://www.youtube.com/watch?v=HxaD_trXwRE
Parser ¶
Parse() is a parser which produces a parse tree from a given set of lexer tokens.
Based on an article by Douglas Crockford: Top Down Operator Precedence
http://crockford.com/javascript/tdop/tdop.html
which is based on the ideas of Vaughan Pratt and his paper: Top Down Operator Precedence
http://portal.acm.org/citation.cfm?id=512931 https://tdop.github.io/
ParseWithRuntime() parses a given input and decorates the resulting parse tree with runtime components which can be used to interpret the parsed query.
Index ¶
Constants ¶
const ( NodeEOF = "EOF" NodeVALUE = "value" NodeTRUE = "true" NodeFALSE = "false" NodeNULL = "null" NodeFUNC = "func" NodeORDERING = "ordering" NodeFILTERING = "filtering" NodeNULLTRAVERSAL = "nulltraversal" NodeCOMMA = "comma" NodeGROUP = "group" NodeEND = "end" NodeAS = "as" NodeFORMAT = "format" NodeGET = "get" NodeLOOKUP = "lookup" NodeFROM = "from" NodeWHERE = "where" NodeUNIQUE = "unique" NodeUNIQUECOUNT = "uniquecount" NodeISNOTNULL = "isnotnull" NodeASCENDING = "asc" NodeDESCENDING = "desc" NodeTRAVERSE = "traverse" NodePRIMARY = "primary" NodeSHOW = "show" NodeSHOWTERM = "showterm" NodeWITH = "with" NodeLIST = "list" NodeOR = "or" NodeAND = "and" NodeNOT = "not" NodeGEQ = ">=" NodeLEQ = "<=" NodeNEQ = "!=" NodeEQ = "=" NodeGT = ">" NodeLT = "<" NodeIN = "in" NodeNOTIN = "notin" NodeLIKE = "like" NodeCONTAINS = "contains" NodeBEGINSWITH = "beginswith" NodeENDSWITH = "endswith" NodeCONTAINSNOT = "containsnot" NodePLUS = "plus" NodeMINUS = "minus" NodeTIMES = "times" NodeDIV = "div" NodeMODINT = "modint" NodeDIVINT = "divint" NodeLPAREN = "(" NodeRPAREN = ")" NodeLBRACK = "[" NodeRBRACK = "]" )
Available parser AST node types
const RuneEOF = -1
RuneEOF is a special rune which represents the end of the input
const TokenSHOWTERM = LexTokenID(-1)
TokenSHOWTERM is an extra token which is generated by the parser to group show terms
Variables ¶
var ( ErrUnexpectedEnd = errors.New("Unexpected end") ErrLexicalError = errors.New("Lexical error") ErrUnknownToken = errors.New("Unknown term") ErrImpossibleNullDenotation = errors.New("Term cannot start an expression") ErrImpossibleLeftDenotation = errors.New("Term can only start an expression") ErrUnexpectedToken = errors.New("Unexpected term") )
Parser related error types
Functions ¶
func PrettyPrint ¶
PrettyPrint produces a pretty printed EQL query from a given AST.
Types ¶
type ASTNode ¶
type ASTNode struct {
Name string // Name of the node
Token *LexToken // Lexer token of this ASTNode
Children []*ASTNode // Child nodes
Runtime Runtime // Runtime component for this ASTNode
// contains filtered or unexported fields
}
ASTNode models a node in the AST
func ASTFromPlain ¶
ASTFromPlain creates an AST from a plain AST. A plain AST is a nested map structure like this:
{
name : <name of node>
value : <value of node>
children : [ <child nodes> ]
}
func ParseWithRuntime ¶
func ParseWithRuntime(name string, input string, rp RuntimeProvider) (*ASTNode, error)
ParseWithRuntime parses a given input string and returns an AST decorated with runtime components.
type Error ¶
type Error struct {
Source string // Name of the source which was given to the parser
Type error // Error type (to be used for equal checks)
Detail string // Details of this error
Line int // Line of the error
Pos int // Position of the error
}
Error models a parser related error
type LexToken ¶
type LexToken struct {
ID LexTokenID // Token kind
Pos int // Starting position (in runes)
Val string // Token value
Lline int // Line in the input this token appears
Lpos int // Position in the input line this token appears
}
LexToken represents a token which is returned by the lexer.
type LexTokenID ¶
type LexTokenID int
LexTokenID represents a unique lexer token ID
const ( TokenError LexTokenID = iota // Lexing error token with a message as val TokenEOF // End-of-file token TokenVALUE // Simple value TokenNODEKIND // Node kind value TokenGeneral // General token used for plain ASTs TOKENodeSYMBOLS // Used to separate symbols from other tokens in this list TokenGEQ TokenLEQ TokenNEQ TokenEQ TokenGT TokenLT TokenLPAREN TokenRPAREN TokenLBRACK TokenRBRACK TokenCOMMA TokenAT TokenPLUS TokenMINUS TokenTIMES TokenDIV TokenDIVINT TokenMODINT TOKENodeKEYWORDS // Used to separate keywords from other tokens in this list TokenGET TokenLOOKUP TokenFROM TokenGROUP TokenWITH TokenLIST TokenNULLTRAVERSAL TokenFILTERING TokenORDERING TokenWHERE TokenTRAVERSE TokenEND TokenPRIMARY TokenSHOW TokenAS TokenFORMAT TokenAND TokenOR TokenLIKE TokenIN TokenCONTAINS TokenBEGINSWITH TokenENDSWITH TokenCONTAINSNOT TokenNOT TokenNOTIN TokenFALSE TokenTRUE TokenUNIQUE TokenUNIQUECOUNT TokenNULL TokenISNULL TokenISNOTNULL TokenASCENDING TokenDESCENDING )
Available lexer token types
type Runtime ¶
type Runtime interface {
/*
Validate this runtime component and all its child components.
*/
Validate() error
/*
Eval evaluate this runtime component.
*/
Eval() (interface{}, error)
}
Runtime provides the runtime for an ASTNode.
type RuntimeProvider ¶
type RuntimeProvider interface {
/*
Runtime returns a runtime component for a given ASTNode.
*/
Runtime(node *ASTNode) Runtime
}
RuntimeProvider provides runtime components for a parse tree.
Source Files