GenericSymbolState

Implements: ISymbolState

Description

The GenericSymbolState class allows you to add multi-character symbols and obtain a symbol token from a scanner.

Important points

• The idea of a symbol is a character that stands on its own, such as an ampersand or a parenthesis.
• For example, when tokenizing the expression (isReady)& (isWilling), a typical tokenizer would return 7 tokens, including one for each parenthesis and one for the ampersand. Thus a series of symbols such as )&( becomes three tokens, while a series of letters such as isReady becomes a single word token.
• Multi-character symbols are an exception to the rule that a symbol is a standalone character.
• For example, a tokenizer may want less-than-or-equals to tokenize as a single token. This class provides a method for establishing which multi-character symbols an object of this class should treat as single symbols. This allows, for example, “cat <= dog” to tokenize as three tokens, rather than splitting the less-than and equals symbols into separate tokens.
• By default, this state recognizes the following multi-character symbols: !=, :-, <=, >=

Instance methods

add

Adds a multi-character symbol.

public add(value: string, tokenType: TokenType): void

• value: string - symbol to add, such as "=:="
• tokenType: TokenType - type of token

nextToken

Returns a symbol token from a scanner.

public nextToken(scanner: IScanner, tokenizer: ITokenizer): Token

• scanner: IScanner - text string to be tokenized.
• tokenizer: ITokenizer - tokenizer class that controls the process.
• returns: Token - next token from the top of the stream.