C Plus Minus

Table of Contents

• C Plus Minus
  • Table of Contents
  • Introduction
  • Run Steps
  • Tools and Technologies
  • Tokens
  • Syntax
    • Data Types
    • Operators
    • Conditional Statements
    • Loops
    • Functions
    • Enumerations
  • Quadruples
    • Procedures
    • Enums
    • Variables
    • Branching & Jumps
    • Arithmetic Operations
    • Bitwise Operations
    • Logical Operations
  • Production Rules
  • Semantic Errors
  • Semantic Errors
  • Desktop Application

Introduction

The designed language is a C like programming language.

Sample program:

const int a = 5;
float b = 6;
print ("Operations:");
if (a == 5) {
    print ("a is 5");
}
else {
    if (b == 6) {
        print ("b is 6");
    }
    else {
        print ("b is not 6");
    }
}
exit;

Run Steps

• yacc -d main.y: create y.tab.h and y.tab.c
• lex main.l: create lex.yy.c
• gcc -g lex.yy.c y.tab.c -o main: create main
• ./main: run main

For convenience, the above steps are combined in a makefile. To run the makefile, type make <test case name> in the terminal.

Tools and Technologies

1. Lex: It breaks down the input text into a sequence of tokens, which are then passed on to the parser for further processing.
2. Yacc: It takes a sequence of tokens as input and produces a parse tree or an abstract syntax tree (AST) that represents the structure of the input according to the grammar rules.

Tokens

Token	Regex	Description
DIGIT	[0-9]	Number between 0 and 9.
ALPHABET	[a-zA-Z]	Upper case or lower case English letter.
ALPHANUM	[0-9a-zA-Z]	Digit, upper case letter, or lower case letter.
SPACE	[ \r\t]	Single space or tab.
NEW_LINE	\n	New line.
INLINE_COMMENT	\/\/.*	Single line comment.
MULTILINE_COMMENT	\/\*.*\*\/	Multi-line comment.
arithmeticOps	[/+*%-]	Arithmetic operators (+, -, *, /, %).
bitwiseOps	[&^~|]	Bit-wise operators (AND, OR, NOT, XOR).
endOfStatement	[;]	Semi-colon to mark the end of any statement.
punctuators	[()={}:,]	Language punctuators.
TRUE	[tT]rue | 1 | [yY]es	True value.
FALSE	[fF]alse| 0 | [nN]o	False value.

Syntax

Data Types

Tha language supports the following data types:

• Integer
• Float
• Boolean
• String

It supports modifiers like const as well.

const int a = 10;
int b = 20;
float c = 10.5;
bool d = true;
string e = "Hello World";

Operators

The language supports the common operators in C.

// Arithmetic operators
a = b + c;
a = b - c;
a = b * c;
a = b / c;
a = b % c;
// Bitwise operators
a = b & c;
a = b | c;
a = b ^ c;
a = ~b;
// Logical operators
a = b && c;
a = b || c;
a = !b;
// Relational operators
a = b == c;
a = b != c;
a = b > c;
a = b >= c;
a = b < c;
a = b <= c;
// Shift operators
a = b << c;
a = b >> c;

Conditional Statements

The language supports the if-else, if-elif-else, and switch-case statements.

int a = 10;
// if statement
if (a == 10) {
    print("if");
    print("another if");
}
elif (a == 11) {
    print("elif");
    print("another elif");
}
else {
    print("else");
    print("another else");
    if (a == 10) {
        print("if");
        print("another if");
    }
    else {
        print("else");
        print("another else");
    }
}
if (a == 10) {
    print("if");
    print("another if");
}
elif(a == 11) {
    print("else");
    print("another else");
}
// switch-case statement
switch (a) {
    default:
        print("default");
        break;
}
switch (a) {
    case 1: 
        print("1");
        break;
    
    case 2: 
        print("2");
        break;
    
    case 3: 
        print("3");
        break;
}

switch (a) {
    case 1: 
        print("1");
        break;
    
    case 2: 
        print("2");
        break;
    
    case 3: 
        print("3");
        break;
    
    default: 
        print("default");
        break;
}

Loops

The language supports the while, for, and repeat-until loops.

// while loop
a = 0;
while (a < 20) {
    print(a);
    a = a + 1;
}
print(a);
while (a < 20) {
    if (a == 10) {
        print(a);
    }
    a = a + 1;
}
// for loop
for (a=2 ; a<10; a = a+1 ) {
    print(a);
}
for (a=2 ; a<10; a= a+1 ) {
    print(a);
    b = a;
    while (b < 10) {
        if (b == 5) {
            print("hi");
            print(b);
        }
        
        b = b + 1;
    }
}
// repeat-until loop
a = 0;
repeat {
    print(a);
    a = a + 1;
    print(a);
} until (a == 1);
repeat {
    print(a);
    a = a + 1;
    if (a == 1) {
        print(a);
    }
} until (a == 1);

Functions

The language supports functions with and without parameters.

int y (){
    print("y");
    return 1;
}
int x(int a, int b) {
    print("add");
    return a + b;
}
x(1, 2); // function call
a = y(); // function call and assignment

N.B.: you can't define a function inside any scope.

Enumerations

The language supports enumerations.

enum Color{
    RED=10,
    GREEN,
    BLUE=12,
    RED
};
{
    Color c1;
    Color c2=RED;
    Color c3=3+5;
}

Quadruples

Procedures

Quadruples	Description	ARG1	ARG2	RES
PROC	Start of a procedure	procedure name
ENDPROC	End of a procedure	procedure name
CALL	Calls a procedure, handles all the stuff related to the PC	procedure name
RET	Return from a procedure, handles all the stuff related to the PC

Enums

Quadruples	Description	ARG1	ARG2	RES
ENUM	Start of an enum	enum name
ENDENUM	End of an enum	enum name

Variables

Quadruples	Description	ARG1	ARG2	RES
PUSH	Push to the stack frame	Identifier/Expr
POP	Pop from the stack frame	Identifier/Expr
CAST	Cast the type of the var on the top of the stack to the type of the var to be pop into

Branching & Jumps

Quadruples	Description	ARG1	ARG2	RES
JMP	Unconditional jump to the label	label
JF	Jumps to the label if the result of the last operation was false	label

Arithmetic Operations

Quadruples	Description	ARG1	ARG2	RES
NEG	Get the opposite sign of an expression
COMPLEMENT	Get the complement of an expression
NOT	Get the bitwise not of an expression
ADD	Add two numbers
SUB	Subtract two numbers
MUL	Multiply two numbers
DIV	Divide two numbers
MOD	Modulus two numbers

Bitwise Operations

Quadruples	Description	ARG1	ARG2	RES
BITWISE_OR	Get the bitwise or of two numbers
BITWISE_AND	Get the bitwise and of two numbers
BITWISE_XOR	Get the bitwise xor of two numbers
SHL	Shift left the number
SHR	Shift right the number

Logical Operations

Quadruples	Description	ARG1	ARG2	RES
LOGICAL_OR	Get the logical or of two numbers
LOGICAL_AND	Get the logical or of two numbers
EQ	Check if two numbers are equal
NEQ	Check if two numbers are not equal
GT	Check if the first number is greater than the second
GEQ	Check if the first number is greater than or equal the second
LT	Check if the first number is less than the second
LEQ	Check if the first number is less than or equal the second

Production Rules

• program → statements | functionDef | statements program | functionDef program


• statements → statement | codeBlock | controlstatement | statements codeBlock | statements statement | statements controlstatement


• codeBlock → { statements } | { }


• controlstatement → ifCondition | whileLoop | forLoop | repeatUntilLoop | switchCaseLoop


• statement → assignment | exp | declaration | EXIT | BREAK | CONTINUE | RETURN | RETURN exp | PRINT ( exp ) | PRINT ( STRING )


• declaration → dataType IDENTIFIER | dataType assignment | dataIdentifier declaration


• assignment → IDENTIFIER = exp | IDENTIFIER = STRING | enumDeclaration | enumDef


• exp → term | functionCall | - term | '~' term | NOT term | exp '+' exp | exp '-' exp | exp '*' exp | exp '/' exp | exp '%' exp | exp '|' exp | exp '&' exp | exp '^' exp | exp SHL exp | exp SHR exp | exp EQ exp | exp NEQ exp | exp GT exp | exp GEQ exp | exp LT exp | exp LEQ exp | exp AND exp | exp OR exp


• term → NUMBER | FLOAT_NUMBER | TRUE_VAL | FALSE_VAL |IDENTIFIER | ( exp )


• dataIdentifier → CONST


• dataType → INT_DATA_TYPE | FLOAT_DATA_TYPE | STRING_DATA_TYPE | BOOL_DATA_TYPE | VOID_DATA_TYPE


• ifCondition → IF ( exp ) codeBlock | IF ( exp ) codeBlock ELSE codeBlock | IF ( exp ) codeBlock ELIF ( exp ) codeBlock | IF ( exp ) codeBlock ELIF ( exp ) codeBlock ELSE codeBlock


• whileLoop → WHILE ( exp ) codeBlock


• forLoop → FOR ( assignment ; exp ; assignment ) codeBlock


• repeatUntilLoop → REPEAT codeBlock UNTIL ( exp ) ;


• case → CASE exp : statements | DEFAULT : statements


• caseList → caseList case | case


• switchCaseLoop → SWITCH ( exp ) { caseList }


• functionArgs → dataType IDENTIFIER | dataType IDENTIFIER , functionArgs


• functionParams → term | term , functionParams


• functionDef → dataType IDENTIFIER ( functionArgs ) codeBlock | dataType IDENTIFIER '(' ')' codeBlock


• functionCall → IDENTIFIER ( functionParams ) | IDENTIFIER ( )


• enumDef → ENUM IDENTIFIER { enumBody }


• enumBody → IDENTIFIER | IDENTIFIER = exp | enumBody , IDENTIFIER | enumBody , IDENTIFIER = exp


• enumDeclaration → IDENTIFIER IDENTIFIER | IDENTIFIER IDENTIFIER = exp

Semantic Errors

Semantic Errors

TYPE_MISMATCH UNDECLARED
UNINITIALIZED UNUSED
REDECLARED
CONSTANT
OUT_OF_SCOPE

Desktop Application

A desktop application is developed using PyQt5 to provide a user interface for the compiler. The application allows the user to select a file from the file system and compile it. The application will then display the generated quadruples, the symbol table, and the results of the executed code.

• The main functionalities:
  • Open an existing file (Ctrl + O)
  • Write a new file in the text editor
  • Save the file (Ctrl + S)
  • Compile the file in one step
  • Compile the file step by step
  • Display the generated quadruples
  • Display the symbol table
  • Display the results of the executed code
  • Highlight the syntax errors in red
  • Highlight the semantic errors in yellow
  • Highlight the semantic warnings in orange
  • Remove the highlights (Ctrl + R)