Class: AjLisp::Parser

Inherits:
Object
  • Object
show all
Defined in:
lib/ajlisp/parser.rb

Instance Method Summary collapse

Constructor Details

#initialize(lexer) ⇒ Parser

Returns a new instance of Parser.



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# File 'lib/ajlisp/parser.rb', line 6

def initialize(lexer)
    @lexer = lexer
end

Instance Method Details

#parseExpression ⇒ Object 



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# File 'lib/ajlisp/parser.rb', line 10

def parseExpression
    token = @lexer.nextToken
    
    if token == nil
        return nil
    end
    
    if token.type == TokenType::ATOM
        if token.value[0,1] == "."
            return DotVerbAtom.new token.value
        end
        
        if token.value[0,1] == "@"
            return AtConstantAtom.new token.value
        end
        
        if token.value[0,1] == "'"
            return List.make [NamedAtom.new("quote"), parseExpression]
        end
        
        if token.value[0,1] == "`"
            return List.make [NamedAtom.new("backquote"), parseExpression]
        end

        if token.value[0,1] == ","
            return List.make [NamedAtom.new("unquote"), parseExpression]
        end
        
        if token.value == "false"
            return false
        end
        
        if token.value == "true"
            return true
        end
        
        if token.value == "nil"
            return NilAtom.instance
        end

        return NamedAtom.new token.value
    end
    
    if token.type == TokenType::INTEGER
        return token.value.to_i
    end
    
    if token.type == TokenType::STRING
        return token.value
    end
    
    if token.type == TokenType::SEPARATOR and token.value == "("
        elements = []
        token = @lexer.nextToken
        
        while not (token.type == TokenType::SEPARATOR and token.value == ")")
            @lexer.pushToken token
            elements.push parseExpression
            token = @lexer.nextToken
        end

        if elements.length == 0
            return EmptyList.instance
        else
            return List::make elements
        end
    end
end