CSE340程序代写、代写C/C++语言编程

日期：2022-03-29 10:11

CSE340 Spring 2021 Project 3: Type Checking

Due: Tuesday, Arpil 1, 2021 by 11:59 pm MST

The goal of this project is to give you experience in Hindley-Milner type checking.

We begin by introducing the grammar of our language which is based on the previous project with

additional constructs. Then we will discuss the semantics of our language and type checking rules.

Finally we will go over a few examples and formalize the expected output.

1. Lexical Specification

Here is the list of tokens that your lexical analyzer should recognize (the new tokens are listed first):

INT = "int"

REAL = "real"

BOOL = "bool"

TRUE = "true"

FALSE = "false"

IF = "if"

WHILE = "while"

SWITCH = "switch"

CASE = "case"

NOT = "!"

PLUS = "+"

MINUS = "-"

MULT = "*"

DIV = "/"

GREATER = ">"

LESS = "<"

GTEQ = ">="

LTEQ = "<="

NOTEQUAL = "<>"

LPAREN = "("

RPAREN = ")"

NUM = (pdigit digit*) + 0

REALNUM = NUM "." digit digit*

PUBLIC = "public"

PRIVATE = "private"

EQUAL = "="

COLON = ":"

COMMA = ","

SEMICOLON = ";"

LBRACE = "{"

RBRACE = "}"

ID = letter (letter + digit)*

2. Grammar

Here is the grammar for our input language:

program -> global_vars body

global_vars -> ε

global_vars -> var_decl_list

var_decl_list -> var_decl

var_decl_list -> var_decl var_decl_list

var_decl -> var_list COLON type_name SEMICOLON

var_list -> ID

var_list -> ID COMMA var_list

type_name -> INT

type_name -> REAL

type_name -> BOOL

body -> LBRACE stmt_list RBRACE

stmt_list -> stmt

stmt_list -> stmt stmt_list

stmt -> assignment_stmt

stmt -> if_stmt

stmt -> while_stmt

stmt -> switch_stmt

assignment_stmt -> ID EQUAL expression SEMICOLON

expression -> primary

expression -> binary_operator expression expression

expression -> unary_operator expression

unary_operator -> NOT

binary_operator -> PLUS | MINUS | MULT | DIV

binary_operator -> GREATER | LESS | GTEQ | LTEQ | EQUAL | NOTEQUAL

primary -> ID

primary -> NUM

primary -> REALNUM

primary -> TRUE

primary -> FALSE

if_stmt -> IF LPAREN expression RPAREN body

while_stmt -> WHILE LPAREN expression RPAREN body

switch_stmt -> SWITCH LPAREN expression RPAREN LBRACE case_list RBRACE

case_list -> case

case_list -> case case_list

case -> CASE NUM COLON body

3. Language Semantics

3.1. Types

The language has three built-in types: int , real and bool .

3.2. Variables

Programmers can declare variables either explicitly or implicitly.

Explicit variables are declared in an var_list of a var_decl .

A variable is declared implicitly if it is not declared explicitly but it appears in the

program body.

Example

Consider the following program written in our language:

x: int;

y: bool;

{

y = x;

z = 10;

w = * z 5;

}

This program has four variables declared: x , y , z , and w , with x and y explicitly declared and z

and w implicitly declared.

3.3. Type System

Our language uses structural equivalence for checking type equivalence. Implicit types will

be inferred from the usage (in a simplified form of Hindley-Milner type inference).

Here are all the type rules/constraints that your type checker will enforce (constraints are

labeled for reference):

C1: The left hand side of an assignment should have the same type as its right hand side

C2: The operands of a binary operator ( GTEQ

, LTEQ , EQUAL and NOTEQUAL

PLUS , MINUS , MULT , DIV , GREATER , LESS , )

should have the same type (it can be any type)

C3: The operand of a unary operator ( NOT ) should be of type bool

C4: Condition of if and while statements should be of type bool

C5: The expression that follows the switch keyword in switch_stmt should be of type

int

The type of expression binary_operator op1 op2 is the same as the type of op1 and

op2 if operator is PLUS , MINUS , MULT or DIV . Note that op1 and op2 must have

the same type due to C2

The type of expression binary_operator op1 op2 is bool if operator is GREATER ,

LESS , GTEQ , LTEQ , EQUAL or NOTEQUAL

The type of expression unary_operator op is bool

NUM constants are of type int

REALNUM constants are of type real

true and false values are of type bool

4. Output

There are two scenarios:

There is a type error in the input program

There are no type errors in the input program

4.1. Type Error

If any of the type constraints (listed in the Type System section above) is violated in the

input program, then the output of your program should be:

TYPE MISMATCH <line_number> <constraint>

Where <line_number> is replaced with the line number that the violation occurs and

<constraint> should be replaced with the label of the violated type constraint (possible values

are C1 through C5). Note that you can assume that anywhere a violation can occur it will be on a

single line.

4.2. No Type Error

If there are no type errors in the input program, then you should output type information for all

variables in the input program in the order they appear in the program. There are two cases:

If the type of the variable is determined to be one of the builtin types, then output one line in

the following format:

<variable>: <type> #

where <variable> should be replaced by the variable name and <type> should be

replaced by the type of the variable.

If the type of the variable could not be determined to be one of the builtin types, then you

need to list all variables that have the same type as the target variable and mark all of

them as printed (so as to not print a separate entry for those later). You should output one

line in the following format:

<variable_list>: ? #

where <variable_list> is a comma-separated list of variables that have the same type

in the order they appear in the program.

5. Examples

Given the following:

a, b: int;

{

a = < b 2;

}

The output will be the following:

TYPE MISMATCH 3 C1

This is because the type of < b 2 is bool , but a is of type int which is a violation of C1.

Given the following:

a, b: int;

{

a = + b 2.5;

}

The output will be the following:

TYPE MISMATCH 3 C2

This is because the type of b is int and the type of 2.5 is real which means in the

expression + b 2.5 , C2 is violated

Given the following:

a, b: int;

{

a = b;

}

The output will be the following:

a: int #

b: int #

Given the following:

{

a = b;

}

The output will be the following:

a, b: ? #

Note that b is not listed separately because it is marked as printed when listed with a on the first

line of the output.

Given the following:

{

a = + 1 b;

}

The output will be the following:

a: int #

b: int #

Given the following:

{

if (<= a b)

{

a = 2.4;

}

}

The output will be the following:

a: real #

b: real #

Given the following:

{

if (a)

{

b = * 2 b;

}

}

The output will be the following:

a: bool #

b: int #

Given the following:

a, b: int;

c: int;

{

x = + a * b c;

y = ! true;

}

The output will be the following:

a: int #

b: int #

c: int #

x: int #

y: bool #

Given the following:

{

x = + a * b c;

y = ! < a x;

z = w;

}

The output will be the following:

x, a, b, c: ? #

y: bool #

z, w: ? #

Note that z and w are not listed with x .

6. Requirements

You should use C/C++, no other programming languages are allowed.

You should submit your code on the course submission website, no other submission

forms will be accepted.

Also submit the output file obtained from the server

7. Evaluation

The submissions are evaluated based on the automated test cases on the submission website.

Your grade will be proportional to the number of test cases passing. If your code does not

compile on the submission website, you will not receive any points.

Here is the breakdown of points for tests in different categories:

Test cases with assignment statements (no if , while or switch ): 50 points

Test cases with assignment, if and while statements (no switch ): 30 points

Test cases with all types of statements: 20 points