Custom Interpreter from scratch

This is a custom interpreter implemented from scratch using C++.

Setup

Add the folder to the system path to allow the interpreter to work anywhere in the system.

create a "test.txt" file and write

print("hello world");

execute the file by executing in the command prompt

interpreter test.txt

Documentation

general

The program execution starts from the first line of the program and proceeds in order till the end of the file.

variables

Two types of variables can be created, string and integer. Any variable declared has a global scope. They can be declared as follows

a = 1;
b = 2 + a;
c = a*b + (2/3);
d = "hello world";

builtin functions

print

use "print" to output anything to the console.

print("hello world");
print("value of a : ", a);

input

use "input" fetch data from the user. it can be used as follows:

a = input("enter value of a: ");

string

"string" is used to convert an integer into string type. This accepts only integer values as argument.

b = str(1) + "23";
print(b);

output:

123

int

"int" is used to convert a string to integer type. This accepts only string values as argument.

b = int("1") + 1;
print(b);

output:

2

len

"len" is used to get the length of the string.

b = len("hello world");
print(b);

output:

11

conditionals

It supports if-else-if ladder like any other language. sample program to check if leap year or not using if-else-if ladder.

year = input("enter year")
if(year % 4 == 0){
	if(year % 100 == 0 and year % 400 != 0){
		print("not a leap year");
	}
	else{
		print("leap year");
	}
}
else{
	print("not a leap year");
}

loops

It supports while loops like any other language. sample program to print numbers from 1 to 10.

a = 1;
while(a <= 10){
	print(a);
	a = a+1;
}

loop controls

break

stops further execution of the loop.

a = 1;
while(a <= 5){
	if(a == 3){
		break;
	}
	print(a, "\n");
	a=a+1;
}

output of the above code:

1
2

continue

stops execution of the current iteration of the loop and proceeds to the next iteration.

a = 1;
while(a <= 5){
	if(a == 3){
		a=a+1;
		continue;
	}
	print(a, "\n");
	a=a+1;
}

output of the above code:

1
2
4
5

Future development scope

1. Add arrays
2. Add advanced string functions
3. Facilitate function creation
4. Add comments