CSE 321 Lab 3

Lab 3 Table of Contents

• Part1
• Part2

Part 1 - Table of Contents

• Objective
• Overview
• Materials Provided
• Set up
• Getting Tokens
• Other Errors
• Using the Test Driver
• What To Submit

Objective

Overview

You will be implementing the Parse operation as an extension to the Program component (see the Program section in the class notes for the specs). Your implementation must use a recursive descent algorithm based on the context-free grammar for BL programs included at the end of this handout. Note, however, that the non-terminal symbols, <program> and <new_instruction>, are not defined recursively in terms of themselves or of each other; therefore, recursion is not called for here in part 1. The non-terminal <program> is defined in terms of <new_instruction>.

In addition, your implementation must check for syntax errors. This can be done by using the assert statement to notify users of syntax errors, just as the assert statement is used to notify users of precondition violations in checking versions of components. The assert statement has two parameters: the condition to be tested and the error message to be displayed if the condition is false. For example,

     assert ((x < 0), "Expecting negative integer.")

For additional examples of how to incorporate an assert statement, look at CT/XYZ/Kernel_C.h in the RESOLVE_Catalog, for a general specification, or at any of the checking versions of specific RESOLVE components.

Note: in implementing the Parse operation for Program in Part 1 of this lab assignment, you will use the Parse_Block operation for Statement that is provided for you in the Bugs_Catalog. In Part 2 of this lab assignment, you will complete your implementation of the parser by implementing also the Parse_Block operation (as well as the Parse operation) for the Statement component.

Materials Provided

The set up instructions will provide you with a user catalog containing the following components and auxiliary items:

• Program_Parse
• Program_Parse_1
• Parser.cpp

• Fill in the operation bodies as indicated in Program_Parse_1.

The test driver for this lab is a BL parser that reads in a BL program and, if no syntax errors are found, outputs a pretty-printed version of the original program. To use a demonstration version of the parser, just execute the command 321_Parser < BL_source_program. If you want to save the output to a file you can use the command 321_Parser < BL_source_program > output_file.

Set Up

1. Copy the lab3-part1 course catalog to your group project directory (/project/c321axnn, where "x" is your section letter and "nn" is your team number):

   cp -r /class/sce/now/321/labs/catalogs/lab3-part1 /project/c321axnn
   

2. Make sure that the new catalog will be accessible to your partner. Perform this action now and as your last act whenever you finish a working session. Not e that 'l' in the chmod command is the letter 'l' ("el"), as in "lock":

   cd /project/c321axnn/lab3-part1
   
   chmod -R g-l,g+rwX .
   
   set-group-ID .
   

3. Look around the new user catalog to familiarize yourself with its contents.

Getting Tokens

Here is an example call to the Get_Next_Non_Separator_Token operation:

m.Get_Next_Non_Separator_Token (str, token_text, token_kind)

enumeration Token_Types
{
    KEYWORD,
    IDENTIFIER,
    CONDITION,
    WHITE_SPACE,
    COMMENT,
    ERROR
};

Note that Get_Next_Non_Separator_Token returns the next non-separator token, i.e., it skips WHITE_SPACE and COMMENT tokens and only returns KEYWORD, IDENTIFIER, CONDITION, and ERROR tokens.

Other Errors

In addition to being responsible for catching any syntax errors in the input BL source program (i.e., determining whether the source program is in the language generated by the context-free grammar for the BL language), your parser is also responsible for checking the following conditions (and if they are not satisfied, an error message should be produced):

1. The identifier at the end of the program must be the same as the identifier at the beginning of the program.
2. The identifier at the end of each new instruction definition must be the same as the identifier at the beginning of the definition.
3. The names of new user-defined instructions must be unique, i.e., there cannot be two user-defined instructions with the same name.
4. The names of new user-defined instructions must not be the name of one of the primitive instructions, i.e., move, turnleft, turnright, infect, or skip.

The parser is not responsible for making sure that no undefined instruction is called in the program nor that no recursion is present in the program. These conditions can be tested much more easily in the code generation phase, so that's where they will be checked.

Using the Test Driver

What To Submit

rcpp-submit c321?? lab3-part1

Part 2 - Table of Contents

• Objective
• Overview
• Materials Provided
• Set up
• What To Submit

Objective

Overview

You will be implementing the Parse operation as an extension to the Statement component (see the Statement section in the class notes for the specs). Your implementation must use a recursive descent algorithm based on the context-free grammar for BL programs included at the end of this handout. It must also check for syntax errors using assert statements, just like in Part 1 of this lab assignment.

Materials Provided

• Statement_Parse
• Statement_Parse_1
• Parser.cpp

• Fill in the operation bodies as indicated in Statement_Parse_1.

Set Up

1. Copy the lab3-part2 course catalog to your group project directory (/project/c321axnn, where "x" is your section letter and "nn" is your team number):

   cp -r /class/sce/now/321/labs/catalogs/lab3-part2 /project/c321axnn
   

2. Make sure that the new catalog will be accessible to your partner. Perform this action now and as your last act whenever you finish a working session. Not e that 'l' in the chmod command is the letter 'l' ("el"), as in "lock":

   cd /project/c321axnn/lab3-part2
   
   chmod -R g-l,g+rwX .
   
   set-group-ID .
   

3. Look around the new user catalog to familiarize yourself with its contents.

By default, the parser in the lab3-part2 catalog will use the implementation of Parse_Program from the Bugs_Catalog. If you would rather use your own implementation from Part 1, you have to copy the following components from your lab3-part1 catalog into your lab3-part2 catalog:

• Program_Parse
• Program_Parse_1

This can be accomplished with the following commands:

    cd /project/c321axnn/lab3-part2

    cp -r /project/c321axnn/lab3-part1/AT/Program AT

    cp -r /project/c321axnn/lab3-part1/CT/Program CT

    chmod -R g-l,g+rwX .

    set-group-ID .

What To Submit

rcpp-submit c321?? lab3-part2