Version: v0.12.1 Latest Latest

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Published: Dec 29, 2021 License: MIT Imports: 13 Imported by: 1



Package ast contains functions and types for parsing a Booklit document into a Node.



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func Parse

func Parse(filename string, b []byte, opts ...Option) (interface{}, error)

Parse parses the data from b using filename as information in the error messages.

func ParseFile

func ParseFile(filename string, opts ...Option) (i interface{}, err error)

ParseFile parses the file identified by filename.

func ParseReader

func ParseReader(filename string, r io.Reader, opts ...Option) (interface{}, error)

ParseReader parses the data from r using filename as information in the error messages.


type Cloner added in v0.11.0

type Cloner interface {
	Clone() interface{}

Cloner is implemented by any value that has a Clone method, which returns a copy of the value. This is mainly used for types which are not passed by value (e.g map, slice, chan) or structs that contain such types.

This is used in conjunction with the global state feature to create proper copies of the state to allow the parser to properly restore the state in the case of backtracking.

type Error added in v0.12.0

type Error struct {
	Inner    error
	Location Location

Error is a parse error along with its location in the source.

func UnpackError added in v0.11.0

func UnpackError(err error) (*Error, bool)

UnpackError converts an internal parse error to an *Error.

type Invoke

type Invoke struct {
	Function  string
	Arguments []Node

	Location Location

Invoke is a function call, e.g. \foo{bar}.

func (Invoke) Method

func (node Invoke) Method() string

Method returns a method name by splitting Function on '-' and title-casing each word.

func (Invoke) Visit

func (node Invoke) Visit(visitor Visitor) error

Visit calls VisitInvoke.

type Location added in v0.11.0

type Location struct {
	Line   int
	Col    int
	Offset int

Location represents the location of a syntax node within the document.

type Node

type Node interface {
	Visit(Visitor) error

Node is a Booklit syntax tree.

type Option

type Option func(*parser) Option

Option is a function that can set an option on the parser. It returns the previous setting as an Option.

func AllowInvalidUTF8 added in v0.11.0

func AllowInvalidUTF8(b bool) Option

AllowInvalidUTF8 creates an Option to allow invalid UTF-8 bytes. Every invalid UTF-8 byte is treated as a utf8.RuneError (U+FFFD) by character class matchers and is matched by the any matcher. The returned matched value, c.text and c.offset are NOT affected.

The default is false.

func Debug

func Debug(b bool) Option

Debug creates an Option to set the debug flag to b. When set to true, debugging information is printed to stdout while parsing.

The default is false.

func Entrypoint added in v0.11.0

func Entrypoint(ruleName string) Option

Entrypoint creates an Option to set the rule name to use as entrypoint. The rule name must have been specified in the -alternate-entrypoints if generating the parser with the -optimize-grammar flag, otherwise it may have been optimized out. Passing an empty string sets the entrypoint to the first rule in the grammar.

The default is to start parsing at the first rule in the grammar.

func GlobalStore

func GlobalStore(key string, value interface{}) Option

GlobalStore creates an Option to set a key to a certain value in the globalStore.

func InitState added in v0.11.0

func InitState(key string, value interface{}) Option

InitState creates an Option to set a key to a certain value in the global "state" store.

func MaxExpressions added in v0.11.0

func MaxExpressions(maxExprCnt uint64) Option

MaxExpressions creates an Option to stop parsing after the provided number of expressions have been parsed, if the value is 0 then the parser will parse for as many steps as needed (possibly an infinite number).

The default for maxExprCnt is 0.

func Memoize

func Memoize(b bool) Option

Memoize creates an Option to set the memoize flag to b. When set to true, the parser will cache all results so each expression is evaluated only once. This guarantees linear parsing time even for pathological cases, at the expense of more memory and slower times for typical cases.

The default is false.

func Recover

func Recover(b bool) Option

Recover creates an Option to set the recover flag to b. When set to true, this causes the parser to recover from panics and convert it to an error. Setting it to false can be useful while debugging to access the full stack trace.

The default is true.

func Statistics added in v0.11.0

func Statistics(stats *Stats, choiceNoMatch string) Option

Statistics adds a user provided Stats struct to the parser to allow the user to process the results after the parsing has finished. Also the key for the "no match" counter is set.

Example usage:

input := "input"
stats := Stats{}
_, err := Parse("input-file", []byte(input), Statistics(&stats, "no match"))
if err != nil {
b, err := json.MarshalIndent(stats.ChoiceAltCnt, "", "  ")
if err != nil {

type Paragraph

type Paragraph []Sequence

Paragraph is a grouping of lines separated by two linebreaks.

func (Paragraph) Visit

func (node Paragraph) Visit(visitor Visitor) error

Visit calls VisitParagraph.

type Preformatted

type Preformatted []Sequence

Preformatted is a grouping of lines, typically parsed

func (Preformatted) Visit

func (node Preformatted) Visit(visitor Visitor) error

Visit calls VisitPreformatted.

type Sequence

type Sequence []Node

Sequence represents adjacent nodes typically within a single line.

func (Sequence) Visit

func (node Sequence) Visit(visitor Visitor) error

Visit calls VisitSequence.

type Stats added in v0.11.0

type Stats struct {
	// ExprCnt counts the number of expressions processed during parsing
	// This value is compared to the maximum number of expressions allowed
	// (set by the MaxExpressions option).
	ExprCnt uint64

	// ChoiceAltCnt is used to count for each ordered choice expression,
	// which alternative is used how may times.
	// These numbers allow to optimize the order of the ordered choice expression
	// to increase the performance of the parser
	// The outer key of ChoiceAltCnt is composed of the name of the rule as well
	// as the line and the column of the ordered choice.
	// The inner key of ChoiceAltCnt is the number (one-based) of the matching alternative.
	// For each alternative the number of matches are counted. If an ordered choice does not
	// match, a special counter is incremented. The name of this counter is set with
	// the parser option Statistics.
	// For an alternative to be included in ChoiceAltCnt, it has to match at least once.
	ChoiceAltCnt map[string]map[string]int

Stats stores some statistics, gathered during parsing

type String

type String string

String is literal text, not including linebreaks.

func (String) Visit

func (node String) Visit(visitor Visitor) error

Visit calls VisitString.

type Visitor

type Visitor interface {
	VisitString(String) error
	VisitInvoke(Invoke) error
	VisitSequence(Sequence) error
	VisitParagraph(Paragraph) error
	VisitPreformatted(Preformatted) error

Visitor is implemented in order to traverse Node.

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