Dummy Lang

A primitive implementation of c function parser using lex, yacc and c

Description

This is the course project for Compiler Construction, Summer 2020. It uses a stack to implement control flow rather than using an AST

Getting Started

To build the program you can run the following command in terminal

make all

Then you can run the code written on a text file ( see the attached test.txt, test2.txt, test3.txt files in the root dir )

./calc < textfilename.txt

And you should see the desired output ( if the feature exists ) in the terminal

Features

1. Supports Arithmetic Operators

   • +
   • -
   • *
   • /
   • %
   • ()
   • - negation

   Input

   // example [ don't forget the semi-colons at the end of the lines ] 
   float x = 2+2-4+(-2)/4*3 ; 
   display x ; 

   Output

   printed 1.500

2. Supports Conditional Operators

   • ==
   • !=
   • >
   • >=
   • <
   • <=
   • ||
   • &&
   • !

   Input

   // example [ don't forget the semi-colons at the end of the lines ] 
   display 2>=2 && 4<=4 ; 
   display (3==3 && 3==1 || 2==2 && !(3==3) ); 

   Output

   printed 1.00
   printed 0.00

3. Supports shorthand operators

   • +=
   • -=
   • *=
   • /=
   • %=
   • variableName++
   • variableName--
   • ++variableName
   • --variableName

   Input

   float x = 100 ; 
   
   display x++;
   display x;
   
   display ++x;
   display x;
   
   float y = 100 ; 
   
   display y--;
   display y;
   display --y;
   display y;

   Output

   Variable x successfully updated 
   
   printed  : 100.000000 
   
   printed  : 101.000000 
   Variable x successfully updated 
   
   printed  : 102.000000 
   
   printed  : 102.000000 
   Variable y successfully updated 
   
   printed  : 100.000000 
   
   printed  : 99.000000 
   Variable y successfully updated 
   
   printed  : 98.000000 
   
   printed  : 98.000000 

4. Supports Variable Declaration

   As of now the only types is float, however the grammar for int is recognized

   example of supported variable declarations ( uninitialized variables throw error and will result in the termination of the program )

   Input

   int v1, v2 , v3 ; // has to end line with semicolon 
   int v1, v2 = 10 ; // v2 has a value of 10.0 however v1 is uninitialized
   float v1=1.0, v2, v3=101.0; // v2 is uninitialized
   
   // the action below is supported aswell 
   float y = 100, z = 500; 
   float x =  y + z  ; // now x will have a value of 600.0 
   \\ trying to use undeclared variables will result in the termination of the program 

5. if-elseif-else and if-elseif-else nested support

   Basic Syntax Rules

   • must be in these format if(c){} or if(c){}else{} or if(c){}elseif(c){}else{} braces without semicolon in the end
   • c means conditional statement of any length

   Input

        if(2<2){
            return 1 ;
        }
        else if(3==4){
            return 2;
        }
        else{
            display 3;
            if(2==2){
                display 3.25; 
                if(3!=3){
                    display 3.5;
                }
                else if(4==2){
                    display 3.75;
                }
                else{
                    display 3.95;
                }
            }
        }
        

   Output

    printed  : 3.000000 
    printed  : 3.250000 
    printed  : 3.950000 

6. Supports Function Declaration

   As of now the only return types are float, void and int,

   • void types cannot return a value
   • int or float types must return a value

   Input - 1

   void foo(){}

   Input - 2

   int foo(){}

   Input - 3

   int foo()
        { 
          return 2+2;
        }

   Output

                                                // output for input 1
      Error Function does not return any value  // output for input 2
      returned : 4                              // output for input 3      

7. Output

   The display command can be used to output results

   • as of now it only supports printing numbers

   Input

   display 2 + 2;
   int x = 4;
   display x+4;
   display 1/2;

   Output

   4.0000
   8.0000
   0.5000