A source-to-source compiler that translates my languages, ATLAS, into C source code. I decided to embark on this project to learn more about: what happens when something is compiled, how C++ and C work, and what it means to design a good programming language.

• Lexer (Tokenizer)
• Parser
• Code Emitter
• "Helper" classes
  • Variable.h
  • optimizer? (Future)

::= <> consists of
{x} <> one or more of x
[x] <> zero or one of x
() <> just grouping
< x > <> one and only one of x
|| <> means or ( like java)
KW <> denotes that the thing is a keyword
TK(S) <> token that we have already defined
nl <> new line
... <> ellipses means pattern

program ::= {statement}
statement ::= KW"WRITE" (expression || TK.StringLiteral) TK.Eos
    || KW."STRING" TK.Identifier TK."=" (TK.StringLiteral || TK.Identifier) TK.Eos
    || KW."INT" TK.Identifier TK."=" (TK.IntLiteral || expression) TK.Eos
    || KW."IF" TKS."){" nl {statement} TKS."};" TK.Eos
    || KW."WHILE" TKS."]{" {statement} TKS"};" TK.Eos
    || KW."INPUT" TK.Identifier TK.Eos
    || KW."FOR" TK."[" KW."INT" TK."]" {statment} TK.EOS
    || TK.identifier TK."=" (TK.StringLiteral || TK.IntLiteral) Tk.Eos
comparison ::= expression {(">" || "<" || ">=" || "<=" || "==" || "!=") expression}
expression ::= term {("+" || "-" term)}
term ::= unary {("*" || "/") unary}
unary ::= ["+" || "-"]primary
primary ::= TK.StringLiteral || TK.identifier || TK.FloatLiteral
TK.Eos = ";" End Of Statement -> EOS

• CC - denotes a comment
• WRITE - standard output function

WRITE "hello world"; CC this will print the given string literal
WRITE a * b + c; CC expressions and variables work as well

• IF - conditional branch

IF [n >= 5]{
    WRITE "n is not 3";
};

• ELSE - conditional branch

IF [n == 0]{
        RETURN 1;
    };

ELSE {
    NUM x = n * 10;
    NUM temp = @mystery(x,); CC calls function and saves value to temp
    RETURN  n * temp + 4;
};

• INPUT - takes input from user

INPUT STRING name; CC INPUT <Data Type> <Variable Name>

WHILE - loop type

CC Print all positive numbers less than a given n
INPUT NUM n;
NUM i = 0;

WHILE [ i < n]{
  WRITE i;
  i = i + 1;
};

• FOR - loop type

CC you can loop for a given amount of times 
INPUT NUM x;

FOR [x]{
    WRITE "Hello";
};

CC you can also loop for the length of a string

FOR ["Strawberry"]{
    WRITE x;
};

• DEFINE - used to define a function

CC DEFINE is followed by the function name
CC within the parameters of the function, local 
CC variable names and datatypes are seperated by a colon 
CC all local parameters are ended by a comma 
CC following the dollar sign, we have the return type
DEFINE factorial (n:NUM,) $ NUM {
  CC returns n! factorial

  IF [n == 0]{
    RETURN 1;
  };

  ELSE {
    NUM x = n - 1;
    NUM temp = @factorial(x,);
    RETURN  n * temp;
  };

  RETURN 1;

};

• RETURN - returns a values within a function
• NUM - a data type

CC all numbers in ATLAS are assumed to be integers unless otherwise specified
NUM x  = 10;

• fl - used to specify a float literal

NUM pi = fl3.14;

• STRING - a data type

STRING name = "Anthony";

• @ - designates a function call

CC here we have our factorial function again
DEFINE factorial (n:NUM,) $ NUM {
  CC returns n! factorial

  IF [n == 0]{
    RETURN 1;
  };

  ELSE {
    NUM x = n - 1;
    NUM temp = @factorial(x,); CC recursive call
    RETURN  n * temp;
  };

  RETURN 1;

};


WRITE "Please enter a number below";
INPUT NUM in;

NUM answer = @factorial(in,); CC call with variable input

WRITE answer;