##JanC Language Interpreter

This interpreter is purely written in C++11. And, MEMORY LEAK is not ensured! You say what? GC is not supported in C++? WTF!&^%$#@!%..

###Compilation and Usage

Under the root directory of the project.

Compilation requires cmake tool:

mkdir build && cd build
cmake ..
make

Run the interpreter after compilation:

./run

Uasge promopt will guide you all the way.

➜  build git:(master) ✗ ./run 
Welcome to JanC Interpreter!

Usage:
1. load FILENAME.janc
2. quit

>> 

###JanC Langauge

This page focuses on the Language features and code demo. For the architecture design details, please follow this link

Why is it called “JanC”? Because it’s syntax style is heavily copied from the C language, and...“Jan” is my English name :)

I’m gonna show you the brief introduction to the language features, and then many small easy code snippets follow to give you concrete impressions.

####Grammar

Program     :: = Statement*
Statement   :: = ST_Block | ST_Var; | ST_Expression; | ST_Func | ST_If | ST_While | ST_Return; | ST_Continue; | ST_Break;
ST_Block    :: = "{" Statement* "}"
ST_Var      :: = var ID ("["Int”]”)? (= Constant)? ;
ST_Func     :: = func ID “(“ (ID,)* “)” ST_Block
ST_If       :: = if “(“ST_Expression”)” Statement (elseif (ST_Expression) Statement)* (else Statement)?
ST_While    :: = while “(“ST_Expression”)” Statement
ST_Return   :: = return ST_Expression
ST_Continue :: = continue
ST_Break    :: = break
ID          :: = String
Constant    :: = Basic | Array
Array       :: = "{" (Basic,)? "}"
Basic       :: = String | Int | Double | Bool

####Features

1. Basic Types: Bool, Int, Double, String, Array
2. Operators
   1. Arithmetics
      • Binary op
        • +, -, *, /
      • Unary op
        • +, -, ++, --
   2. Relation

      • , >=, <, <=, ==, !=

   3. Logic
      • &&, ||, !
   4. Assignment
      • =
3. Expression
4. Variables: var with Type Inference
5. Function: func
6. if-elseif-else
7. while

Features To Do:

1. Comment
2. return ref from functions (abstract the id of Reference into Reference itself)

####Data Types and Operators

Bool

var b = true;
if (b)
    b = false;
print(b);
print(!b);

false
true

Int

var num = 4;
print(++num);
print(num++);
print(num);
num = num / 2;
print(+num);
print(-num);

5
5
6
3
-3

Double

num = 2.5;
print(num);

3.5

String

var str = "hello";
print(str, "world");
str = str + " world";
print(str);
var secp = "\"\"\"";
print (secp);

"hello" "world"
"hello world"
"""""

Array

Array elements are not restricted to one specific type. You can mix up elements of several types in one Array.

var arr[] = {true, 1, 2.5, "string"};
print("len:", len(arr));
print(arr);
arr[0] = false;
print(arr[0]);

"len:" 4
[true, 1, 2.5, "string", ]
false

You can run the code sample above, type.janc, which can be found in doc directory.

>> load ../doc/type.janc
false
true
5
5
6
3
-3
3.5
"hello" "world"
"hello world"
"""""
"len:" 4
[true, 1, 2.5, "string", ]
false

####If-elseif-else

The code block within the conditional structure can be surrounded be curly brace {...}, or simply use a single statement ending with ;

func test_if(i) {
    if (i == 1) {
        print(1);
    }
    elseif (i == 2) {
        print (2);
    }
    else {
        print ("neither 1 nor 2");
    }
}

test_if(1);
test_if(2);
test_if(3);

>> load ../doc/ifs.janc
1
2
"neither 1 nor 2"

####while

Surely, you can use break and continue as you are used to do.

var cnt = 0;
while(true) {
    cnt++;
    if (cnt <= 3) {
        print(cnt);
        continue;
    }
    break;
}

load ../doc/while.janc
1
2
3

####func

As you can see above, functions are defined with keyword func. It’s able to accept literals, variables, arrays as it’s parameters, as well as it’s return value;

Also, currently there are only two Built-in Functions supported- len(ARRAY) and print(...), whose meanings are quite self-explanatory.

func add (x, y) {
    return x+y;
}

print(add(1, 1));
print(add(1, 2.5));
print(add("hello", " world"));

>> load ../doc/func.janc
2
3.5
"hello world"

###Extra Notes

• Variables and Functions must be declared and defined before used.
• Array size can be declared explicitly, and they will be set as 0 if not initialized.

var arr[5] = {1,2,3};
print("len:", len(arr), arr);
arr[4] = 4;
print(arr[4]);

>> load ../doc/array.janc
"len:" 5 [1, 2, 3, 0, 0, ]
4

• For String, " is available by escaping \"
• For Expression, () can be added to enforce precedence, otherwise the expressions are evaluated by the default precedence of operations, same as C.

###The End

We’d end with a complete program written in JanC- Bubble Sort :-P

func bubble_sort(arr) {
    var l = len(arr);
    var beg = 0;
    while(beg < l) {
        var cur = l-1;
        while(cur > beg) {
            if (arr[cur] < arr[cur-1]) {
                var tmp = arr[cur];
                arr[cur] = arr[cur-1];
                arr[cur-1] = tmp;
            }
            cur--;
        }
        beg++;
    }
}

var ls[] = {5,2,5,3,7,1,10};
bubble_sort(ls);
print(ls);

>> load ../doc/bubble.janc
[1, 2, 3, 5, 5, 7, 10, ]