LanguageCreator

A place to practice language creation mechanisms. Currently can execute a weird minimal language inspired by c# and f#. It properly contructs an AST, validates scoping rules, infer types, and properly uses encapsulated memory spaces.

Supported Constructs

The language supports:

• variable assignment
• if/else conditionals declaration
• function declaration with variable arguments
• anonymous functions
• quoted strings
• simple type inference
• basic classes (no inheritance)
• exception handling
• nil support
• partial function creation and application

Supported built in types are:

• int
• float
• string
• void
• bool (Booleans are true and false)

Operations are:

• +
• -
• & (and)
• || (or)
• /
• ^

Regarding type inference:

• Anonymous lambdas can take arguments and return values when stored in a type inferred "var" variable
• Regular functions can also be declared as "var" and type inferred from their return types
• You can enforce static typing rules by giving a function a proper type, otherwise it'll just use the return type
• If no return statement exists it'll default to void.

Closures can reference their parent's memory space but not their callers memory space.

If a class has a function called init then that is treated as the constructor and is called when a class is created.

Class instantiation is scala style, it is just top down. If a statement isn't enclosed in a function it will be executed before calling the init function.

Example1

void foo(int x){
    if(x > 2){
        print ((x + 1) + 2);
    }
    else{
        print (x);
    }
}
foo(1);
foo(100);

1
103

Example2

var x = fun(int arg) -> {
    int g = arg;
    while(g > 0){
        print g;
        g = g - 1;
    }
    print "done!";
}

var y = x;

var z = y;

z(5);

print "lambda assigments work!";

z(3);

int a = 1;

int b = a;
                    
int c = b;

print c;

5
4
3
2
1
done!
lambda assigments work!
3
2
1
done!
1

Example3

var foo(string t){
    var x = "test";
    return x + t;
}

print foo("pong");

testpong

Example4 (currying)

var func(string printer, int x){
    print printer;
    print x;
}
            
var curry = func("anton");

curry(1);

curry(2);

var otherCurry = func("test");

otherCurry(3);

anton
1
anton
2
test
3

Example 5 (classes)

class anton{
    int x = 1;
    int y = 2;

    void foo(){
        print x;
    }
             
}

var ant = new anton();
var foo = new anton();
    
foo.x = 2;

ant.foo();                

foo.foo();

foo.x = 10;

foo.foo();

1
2
10

Example 6

class bob{
    var z = 1;
}

class anton{
    var x = new bob();
    int y = 0;
}

anton foo = new anton();

print foo.x.z;

1

Example 7

class bob{
    var z = 1;
                    
}

class anton{
    var x = new bob();
    int y = 0;
}

anton foo = new anton();

print foo.x.z;

foo.x.z = 2;

print foo.x.z;

1
2

Example 8

class anton{
    var x = fun() -> { return new anton(); };
    int y = 10;
}

var x = new anton();

var dynamicAnton = x.x();

dynamicAnton.y = 52;

print dynamicAnton.y;

52

Example 9 (forward referencing and object passing)

class human{
    void init(string id){
        age = 99;
        name = id;
    }

    void create(){
        person = new human('test');
    }

    int age;
    string name;

    human person;
}

var person = new human('anton');

void printPerson(human person){
    print 'age of  ' + person.name + ' = ';
    print person.age;
    print '----';
}

person.age = 29;
person.create();            

printPerson(person);

printPerson(person.person);

age of  anton = 
29
----
age of  jane doe = 
99
----

Example 10 basic closures

class bob{
    int x = 0;
    string pr1(method x){
        return x('test') + ' in class bob pr1';   
    }
}

class human{
    int x = 1;
                    
    var b = new bob();

    void pr(method z){                                                                     
        print b.pr1(z) + ' from class human pr';
    }
}

var a = new human();
var b = new bob();

int x = 100;
var lambda = fun(string v) ->{
                    var p = fun() -> { 
                                x = x + 1;
                                print x;
                                print v + ' in second lambda'; 
                            };
                    p();
                    return v;      
                };

a.pr(lambda);

print b.pr1(lambda) + ' from main';

print x;

101
test in second lambda
test in class bob pr1 from class human pr
102
test in second lambda
test in class bob pr1 from main
102

Example 11 (basic reference linking)

int x = 1;

int y = &x;

print y;

y = 2;

print x;   

y = 3;

print x;             

x = 4;

print y;

1
2
3
4

Example 12 (complex reference linking passing via different memory scopes)

class bob{
    int x = 0;
    string pr1(method x){
        return x('test') + ' in class bob pr1';   
    }
}

class human{
    int x = 1;
                    
    var b = new bob();

    void pr(method z){                                                                     
        print b.pr1(z) + ' from class human pr';
    }
}

var a = new human();
var b = new bob();

int y = 100;
int f = &y;
int x = &f;
                

var lambda = fun(string v) ->{
                    var p = fun() -> { 
                                x = x + 1;
                                print x;
                                print v + ' in second lambda'; 
                            };
                    p();
                    return v;      
                };

a.pr(lambda);

print b.pr1(lambda) + ' from main';

print y;

101
test in second lambda
test in class bob pr1 from class human pr
102
test in second lambda
test in class bob pr1 from main
102

(note, this is supposed to have the same result as example 10 which has no links)

Example 13 - nil comparison

void printNull(int item){
    if(item == nil){
        print 'is nil';
    }
    else {
        print 'is not nil';
    }
}

int x;
                
int y = 1;
                
printNull(x);
printNull(y);
    
x = 2;

printNull(x);

is nil
is not nil
is not nil

Example 14 - simple exception handling

class test{
    int x;
}

test item;

try{
    print item.x;
}
catch{
    print 'exception!';
}

exception!

Notes

Type promotion doesn't exist and neither does inheritance. So you can't print a string and an int on the same line because the expression won't match properly, but thats intentional right now.