CMSC 430

CMSC 430 Project 4

The fourth project involves modifying the semantic analyzer for the attached compiler by adding

checks for semantic errors. The static semantic rules of this language are the following:

Variable and parameter names have local scope. The scope rules require that all names be

declared and prohibit duplicate names within the same scope. The type correspondence rules are

as follows:

 Both expressions in the when statement must be the same type

 The type of the switch expression must be Integer.

 All the case statements in a switch statement must match in type. No coercion is

performed.

 Arithmetic operators can only be used with numeric types.

 All list elements must be of the same type.

 In a list variable declaration, the type of the list must match the type of the elements.

 List subscripts must be integer expressions.

 Character literals can be compared to one another but they cannot be compared to

numeric expressions.

 Only integer operands can be used with the remainder operator.

 All the statements in an if statement must match in type. No coercion is performed.

 In a fold statement, the list must be a numeric type.

 A narrowing variable initialization or function return error occurs when a real value is

being forced into integer. Widening is permitted. In all other cases, the type must match.

Type coercion from an integer to a real type is performed within arithmetic expressions.

You must make the following semantic checks. Those highlighted in yellow are already

performed by the code that you have been provided, although you are must make minor

modifications to account for the addition of real types and the need to perform type coercion and

to handle the additional arithmetic, relational and logical operators.

 Type Mismatch on Variable Initialization

 When Types Mismatch

 Switch Expression Not Integer

 Case Types Mismatch

 Arithmetic Operator Requires Numeric Types

 Undeclared Scalar

 Undeclared List

 List Element Types Do Not Match

 List Type Does Not Match Element Types

 List Subscript Must Be Integer

 Character Literals Cannot be Compared to Numeric Expressions

 Remainder Operator Requires Integer Operands

 If-Elsif-Else Type Mismatch

 Fold Requires A Numeric List

 Illegal Narrowing Variable Initialization

 Illegal Narrowing Function Return

 Type Mismatch on Function Return

 Duplicate Scalar

 Duplicate List

This project requires modification to the bison input file, so that it defines the additional

semantic checks necessary to produce these errors and addition of functions to the library of type

checking functions already provided in types.cc. You must also make some modifications to

the functions provided. You need to add a check to the checkAssignment function for

mismatched types in the case that nonnumeric and numeric types are mixed. You need to also

add code to the checkArithmetic function to coerce integers to reals when the types are mixed.

The provided code includes a template class Symbols that defines the symbol table. It already

includes a check for undeclared identifiers. You need to add a check for duplicate identifiers.

Like the lexical and syntax errors, the compiler should display the semantic errors in the

compilation listing, after the line in which they occur. An example of a compilation listing output

containing semantic errors is shown below:

1 // Multiple Semantic Errors

2

3 function main returns integer;

4 value: integer is 4.5;

Semantic Error, Illegal Narrowing Variable Initialization

5 numbers: list of real is (1, 2, 3);

Semantic Error, List Type Does Not Match Element Types

6 one: integer is '1';

Semantic Error, Type Mismatch on Variable Initialization

7 begin

8 if value > 0 then

9 fold left + ('a', 'b') endfold;

Semantic Error, Fold Requires A Numeric List

10 elsif name = 'N' then

Semantic Error, Undeclared Scalar name

11 fold right * (1, 2.5) endfold;

Semantic Error, List Element Types Do Not Match

12 else

13 when value < 10, 1 : 1.5;

Semantic Error, When Types Mismatch

14 endif;

15 end;

Lexical Errors 0

Syntax Errors 0

Semantic Errors 7

You are to submit two files.

1. The first is a .zip file that contains all the source code for the project. The .zip file

should contain the flex input file, which should be a .l file, the bison file, which should

be a .y file, all .cc and .h files and a makefile that builds the project.

2. The second is a Word document (PDF or RTF is also acceptable) that contains the

documentation for the project, which should include the following:

a. A discussion of how you approached the project

b. A test plan that includes test cases that you have created indicating what aspects

of the program each one is testing and a screen shot of your compiler run on that

test case

c. A discussion of lessons learned from the project and any improvements that could

be made