LexicalAnalyzer

public protocol LexicalAnalyzer : AnyObject

The job of an implementation of this protocol is two fold

  • Manage the state of the Scanner to provide n lookahead capability to the surrounding rules
  • To provide a layer of abstraction between consumers of scanning behaviour and the scanner itself. This allows the scanner to be as simple as possible

It used heavily during Rule evaluation. Typically a rule will start by mark()ing it’s possition (remembering the positiong of the Scanner at the start of rule evaluation. During Rule evaluation rules will result (eventually) in calls to the various scan methods which will advance the Scanner. Finally, the rule will either be satisfied and proceed()->LexicalContext will be called, or fail and rewind() will be called returning the Scanner to its state before mark() was called.

  • Creates a new instance of Lexer for the supplied String.

    Declaration

    Swift

    init(source: String)

    Parameters

    source

    The String to perform the lexical analysis on

  • The character currently being evaluated

    Declaration

    Swift

    var current: String { get }

  • The depth of the look-ahead stack

    Declaration

    Swift

    var depth: Int { get }

  • : Marks the current position. This must be followed by a matching rewind() or proceed()

    Declaration

    Swift

    func mark()

  • Marks the current location and signifies that the scanning is actually skipping

    Declaration

    Swift

    func mark(skipping: Bool)

  • : Discards the current mark, rewinding the scanner to that position

    Declaration

    Swift

    func rewind()

  • : Discards the current mark, but leaving the scanner at it’s current location

    Declaration

    Swift

    func proceed() -> LexicalContext

  • Should return true if the end of the source String has been reached

    Declaration

    Swift

    var endOfInput: Bool { get }

  • Scan until the specified terminal is reached in the source String. If the end of the String is reached before the supplied String is matched an error should be thrown. If the terminal is matched, the scanning position should be at the end of that match.

    See also

    scanUpTo(terminal:String)

    Declaration

    Swift

    func scan(terminal: String) throws

    Parameters

    terminal

    A string to scan for

  • Scan until one of the characters in the supplied CharacterSet is found. If the end of the source is reached before a character from the set is found an Error should be thrown. The scanner position should be directly after the matched character.

    Declaration

    Swift

    func scan(oneOf: CharacterSet) throws

    Parameters

    oneOf

    A CharacterSet to scan for

  • Scan the supplied regular expression (NSRegularExpression). If not found an Error should be the thrown. The scanner position should be directly after the matched pattern.

    Declaration

    Swift

    func scan(regularExpression: NSRegularExpression) throws

    Parameters

    regularExpression

    The NSRegularExpression to scan for

  • Scan up to (that is, the position of the scanner should be at the start of the match, not after it) the supplied String. If the terminal is not found an Error should be thrown. The scanner position should be at the first character of the matched terminal.

    See also

    scan(terminal:String)

    Declaration

    Swift

    func scanUpTo(terminal: String) throws

    Parameters

    terminal

    A string to scan for

  • Scan up to one of the characters in the supplied CharacterSet is found. If the end of the source is reached before a character from the set is found an Error should be thrown. The scanner position should be directly at the matched character.

    Declaration

    Swift

    func scanUpTo(oneOf terminal: CharacterSet) throws

    Parameters

    oneOf

    A CharacterSet to scan for

  • Advances the scanner one character. If the end of the source String has already been reached a Error should be thrown.

    Declaration

    Swift

    func scanNext() throws

  • Should return the String from the source representing the supplied range.

    Declaration

    Swift

    subscript(range: Range<String.UnicodeScalarView.Index>) -> String { get }

  • Should return the String being analyzed

    Declaration

    Swift

    var source: String { get }

  • Should return the integer offset of the current scanning position in charactes

    Declaration

    Swift

    var position: Int { get }

  • Should return the String.UnicodeScalarView.Index of the current scanning position in the supplied source String

    Declaration

    Swift

    var index: String.UnicodeScalarView.Index { get set }