octav47/interpreter-egg

A little language implemention on javascript.

Egg

A little language named Egg implemented above javascript.

It's simple. But support function closures, high-order functions and so on. And it could include nearly any logic you could imagine.

Just for fun, origin from my favorite Eloquent Javascript。

All just for fun.

Syntax

All is expressions. Valid expression are string/number/word/application.

do(define (total, 0),     # Hey Egg!
   define (count, 1),
   while(<(count, 11),
         do(define(total, +(total, count)),
            define(count, +(count, 1)))),
   print(total))

Comment

# used for comment

+(1, 2) # plus 1 and 2

do

Run multiple expressions one by one. Return the last expression.

do(expr1[, expr2[, expr3[, ...]]])

values

Valid values include string, number, true and false.

1
"hack"
true
false

word

A name represent variables like values, function, nearly everything.

a
hehe
define
do
print

if

Return different value depending on conditions;

if(condition_expression, true_expression, false_expression)

while

Just like while in other languages. Return false.

while(condition_expression, expression)

define

Define a variable in current scope. Return expression's returned value

define(word, expression)

set

Set variables out of current scope, if there isn't exist, throw ReferenceError. Return the newly set value.

set(word, expression)

+ - * / == < >

Just as you see in other languages. These calculations are supported.

+(1, 2)
>(4, -(2, 1))

fun

define a function. the last arguments will be the function body, all other arguments will be seen as arguments for this function.

do(define(add, fun(a, b, +(a, b))),
   print(add(1, 2)))

Comment

A comment is started with # in a line.

print(1) # a comment

REPL

Run egg.js，just input your code line by line. Ctrl-D or Ctrl-Cto exit:

┌─[reverland@reverland-R478-R429] - [~/tmp/eloquentjs] - [2015-11-12 03:16:54]
└─[0] <git:(master 976b113✱✈) > node egg.js
> do(define (total, 0),
> ..define (count, 1),
> ..while(<(count, 11),
> ....do(define(total, +(total, count)),
> ......define(count, +(count, 1)))),
> ..print(total))
55

TODO

• more tests...
• repl
• compiler
• better parser. learn how Lex and Yacc works.
• evaluate when parse(JIT? 😂)
• reread [Eloquent Javascript] and have fun with it 😊