Package slogo.parser

This package is responsible for parsing the language SLogo.

See:
Description

Interface Summary

Parser

Class Summary

AssignmentParser	Parse an assignment statement, which is looks like
BackParser
CleanParser
ClearScreenParser
DifferenceParser
EqualParser
ForwardParser
GreaterParser
HeadingParser
HideTurtleParser
HomeParser
IdentifierParser
IfParser
InstructionNames
InstructionParser	Instruction Parser - calls appropriate Parser for each Instruction
IsPenDownParser
LeftParser
LessParser
MinusParser
NotEqualParser
NumericExpressionParser	Handles parsing numeric values
PenDownParser
PenUpParser
ProductParser
QuotientParser
RemainderParser
RepeatParser	Parse a REPEAT Statement, which looks like REPEAT numOrVar [ instructionlist ]
RightParser
SetPenColorParser	Parses the SETPENCOLOR instruction
SetXParser
SetXYParser
SetYParser
ShowTurtleParser
SLogoParser	Illustrates the java.io.StreamTokenizer class and how it can be used to parse tokens for a toy example programming language (elan).
StrictInstructionListParser
SumParser
ToParser
TowardsParser
XCorParser
YCorParser

Exception Summary

ParseException

Package slogo.parser Description

This package is responsible for parsing the language SLogo. It uses recursive descent with, currently, no lookahead.

Adding/Parsing a New Instruction

To parse a new instruction the following steps are followed. We'll use the addition of a statement for an If instruction to the language as an example.

1. Create a token for the instruction (probably a subclass of token.ReservedToken) with the same prefix as the new instruction, e.g., IfToken.java.

2. Create a parser for the instruction with the same prefix as the instruction, e.g., IfParser.java. The parsing class (presumably implementing Parser) will return an instance of the parsed Instruction, see the next item.

3. Create an instruction with prefix name, e.g., If.java in the slogo.instruction package.

4. Add the instruction name to the file instructions.prop, e.g., add a single line to the file containing the string If.