CS F363 Compiler Construction
Programming Assignment

Team Members

[2019A7PS0086H] Amogh Bharadwaj

[2019A7PS0164H] Nandan H R

[2019A7PS0033H] T V Chandra Vamsi

Running the compiler:

usage: python3 compile.py [-h] [--tokenize] [--parseOnly] [--tokenPath TOKENPATH] [--stackPath STACKPATH] [--ICPath ICPATH] filepath

Langwej frontend compiler.

positional arguments:
  filepath              Specifies the path to the .lwj file to be compiled

optional arguments:
  -h, --help            show this help message and exit
  --tokenize            Specify this flag if the program needs to be tokenized only, defaults to False
  --parseOnly           Specify this flag if intermediate code should not be generated, defaults to False
  --tokenPath TOKENPATH
                        Specifies the file where tokens are written, defaults to parseTokens.txt
  --stackPath STACKPATH
                        Specifies the file where parse stack traces are written, defaults to parseStack.txt
  --ICPath ICPATH       Specifies the path where intermediate code generated is written, defaults to parseIC.txt

Error Recovery for Parser:

1. Error recovery for extra closing parenthesis (error code e0):

Examples:

let x = (a + b));
               ^
whil (a > b) { a = a + 1); }
                        ^

Recovery Method:

1. Report the error.
2. Skip the closing parenthesis and get the next token.
3. Continue parsing.

2. Error recovery for extra closing brace (error code e1):

Examples:

if (a > b) { a = a + 1; }} else { a = a - 1; }
                         ^
intijur funkshun recursion () {coll recursion();}}
                                                 ^

Recovery Method:

1. Report the error.
2. Skip the closing brace and get the next token.
3. Continue parsing.

3. Panic Mode Recovery (error code ee):

Any error that is not handled by the above recovery methods will be handled by panic mode recovery.

Recovery Method:

1. Report syntax error.
2. T is the next token in the input.

if nextToken does not exist:
    finish parsing
else: 
    while T is not ';' or '}':
        skip T and get the token after T if exists

3. If parser reaches here, it means that the next token, T is either ; or }
S is the current top of the stack.
   pt[S, T] corresponds to the cell in the parse table with S as the top of stack and T as the next token in the input.

while S is not 0 and pt[S, T] is an error:
    pop from stack twice

if S is 0:
    skip T and finish parsing
else:
    leave panic mode and continue parsing