Simple Programming Language (SPL) Compiler

Description

This project is a compiler for a programming language capable of:

1. Integer-type Variables
2. Basic Arithmetic (addition, subtraction, multiplication, integer division)
3. Boolean Logic Operators (less-than, greater-than, not)
4. Conditional Statements (if, switch)
5. Iterative Statements (while, for)
6. Outputting variable values to stdout

Usage

This compiler takes programs written in a text file as input via redirection, and provides any output to stdout.

      ex.) $ ./a.out < program.txt

A program written in the compiler-specific language is composed of three sections (in order):

1. A Variable Declaration Section
2. A Body Section
3. An Input Section

The Variable Declaration Section

Variables are declared at the top of a file (before the body section) with the following syntax:

form: a, b;

The Body Section

This section is enclosed in curly-brackets.

The body section can consist of the following statements:

---

1.) Variable Initialization

    form 1 - initialization from input section: input <variable name>;

      note: inputs are assigned to variables in the order in which they are provided in the inputs section.

      ex.) input G;

        G will equal the int-value x if the input section consists of "x, w" (where x is an integer, and w is a potentially empty list of integers         delimited by commas) at execution-time.

    form 2 - explicit initialization: input <integer literal>;

      ex.) G = 5;

        G will equal 5 at execution-time.

---

2.) Basic Arithmetic Operations

    form: <var> = <var or literal> <operator> <var or literal>;

      ex.) G = 1 + 2; \\ G now holds the value of 3

      ex.) sum = sum - 1; \\ sum has been decremented by 1

      ex.) growth = original * 2; \\ growth now holds double the amount of original

      ex.) x = 7 / 2; \\ x now holds the value of 3

---

3.) Boolean Logic and Conditional/Looping statements

    if form: IF <variable or name> <boolean operator> <variable or name> { <statements> }

      ex.) IF G < 0 { ... } \\ enters IF block if the value in G is negative

      ex.) IF answerToUniverse <> 42 { ... } \\ enters IF block if answerToUniverse does not equal 42

    while form: WHILE <variable or name> <boolean operator> <variable or name> { <statements> }

      ex.) WHILE i > 0 { ... } \\ enters and loops through WHILE block while the value in i is greater than zero

    switch form: SWITCH <variable or name> { CASE x: { ... } CASE y: { ... } ... } \\ where x and y are integer literals

      ex.)

SWITCH a {
  CASE 1: { output a; }
  CASE 2: { a = a - 50; }
  CASE 3: { output b; }
}

---

4.) Output Statements

    form: output <variable>;

      ex.) output a; \\ outputs the value stored in a

The User Input Section

This section is a line at the bottom of the program that consists of a non-empty list of integers. There must be a sufficient number of integers specified in this line for all INPUT statements (There cannot be more INPUT statements than there are user inputs).

      ex.) -3 1 4 1 5 9

Simple Examples

Program_1.txt

i, j;
{
	input i;
  	i = 42 ;
  	j = i + 1; 
	output i;
	output j;
}
1 2 

Terminal output

$ ./a.out < Program_1.txt
42 43

Program_2.txt

j, i, minusfour, k ;

{

input i;
input j;
minusfour = 0-4;

WHILE i > 0 {
	j = 3;	
	IF j > 1 {	
		WHILE j > 0 {
			k = i*j;
			output k;
			j = j-1;
		}
	}
	IF j > 0 {
		WHILE j > 0 {
			k = i*j;
			output k;
			j = j-1;
		}
	}
	i = i-1;
}

input minusfour;

WHILE i > minusfour {
	output i;
	i = i - 1;
}

i = i+1;
j = j+1;
output i;
output j;

}
4 3 4 4 5 2 6

Terminal Output

$ ./a.out < Program_1.txt
12 8 4 9 6 3 6 4 2 3 2 1 1 1