jen is a scripting language meant to be your new best friend! Drawing inspiration from JavaScript, Python, Go, Typescript's sum type, and even Elm, jen provides a pleasant and happy programming experience for all your high level needs. jen's type system provides expressiveness, but also watches your back to prevent head-scratching type errors. With conciseness, elegance, and functionality, jen works hard as a language so you don't have to!
The ohm grammar source file can be found on https://github.com/jtorre39/jen/blob/master/syntax/jen.ohm.
Jen {
Program = newLine* Body newLine*
Body = Statement*
Suite = newLine* indent Body dedent
Statement = Conditional
| Loop
| Declaration newLine+ -- declaration
| Assignment newLine+ -- assignment
| FuncCall newLine+ -- call
| FuncDec
| TypeDec newLine+ -- typedec
| Return newLine+ -- return
| "break" newLine+ -- break
| Expression newLine+ -- expression
Expression = (Exp0 "?" Expression ":" Expression) -- ternary
| Exp0
Exp0 = Exp0 "&&" Exp1 -- and
| Exp0 "||" Exp1 -- or
| Exp0 "&!&" Exp1 -- xor
| Exp1
Exp1 = (Exp1 relop Exp2) -- binary
| Exp2
Exp2 = (Exp2 addop Exp3) -- binary
| Exp3
Exp3 = (Exp3 mulop Exp4) -- binary
| Exp4
Exp4 = (Exp4 "^" Exp5) -- binary
| Exp5
Exp5 = "!" Exp5 -- not
| Exp6
Exp6 = FuncCall
| Exp6 "." id -- accessor
| Exp7
Exp7 = numLiteral
| stringLiteral
| RecordLiteral
| SubscriptExp
| VariableExpression
| booleanLiteral
| errLiteral
| List
| "(" Expression ")" -- parens
VariableExpression = id
VariableExpressions
= NonemptyListOf<VariableExpression, ",">
SubscriptExp = VariableExpression "[" Expression "]"
List = "[" ListOf<Expression, ","> "]"
NonemptyExpressionList
= NonemptyListOf<Expression, ",">
Loop = For | While
For = "for" NonemptyListOf<id, ","> "in" Expression ":" Suite
While = "while" Expression ":" Suite
FuncDec = Annotation newLine Signature newLine Suite
Annotation = (varId | constId) ":" ParamTypes "->" ParamTypes
ParamTypes = NonemptyListOf<Type, ",">
Signature = (varId | constId) "(" Params "):"
Params = ListOf<varId, ",">
Return = "return" ListOf<Expression, ",">
FuncCall = ( Exp6_accessor | SubscriptExp | VariableExpression) "(" ListOf<Expression, ","> ")"
TypeDec = "type" varId ":" SumType
Declaration = Ids ":=" NonemptyExpressionList
Assignment = (SubscriptExp | VariableExpressions)"=" NonemptyExpressionList
Conditional = "if" Expression ":" Suite ("else if" Expression ":" Suite)* ("else" ":" Suite)?
id = varId | constId
Ids = NonemptyListOf<(SubscriptExp | id), ",">
keyword = (basicType | "while" | "else" | "for" | "else if"
| "true" | "false" | "return" | "break" | "type" | "ok"
| "err" | "list") ~idrest
idrest = "_" | alnum
varId = ~keyword ("_" | lower) idrest*
constId = upper ("_" | upper | digit)* ~lower
Type = ListType | RecordType | VariableExpression | basicType
basicType = "string" | "boolean" | "number" | "record"
| "any" | "void" | "error"
ListType = "list"+ ( basicType | RecordType | VariableExpression )
SumType = Type "|" Type ("|" Type)*
RecordType = "{" NonemptyListOf<Field, ","> "}"
Field = id ":" Type
FieldValue = id ":" Expression
RecordLiteral = "{" NonemptyListOf<FieldValue, ","> "}"
booleanLiteral = "true" | "false"
errLiteral = "ok" | "err"
numLiteral = digit+ ("." digit+)?
stringLiteral = "\"" (~"\"" char | "'")* "\""
| "'" (~"'"char | "\"")* "'"
char = escape
| ~";" ~newLine any
addop = "+" | "-"
mulop = "*" | "%" | "//" | "/%" | "/"
relop = "<=" | ">=" | ">" | "<" | "==" | "!="
escape = "\\n" | "\\"
space := " " | "\t" | comment
newLine = "\r"? "\n"
comment = ";" ~";" (~newLine ~";" any)* -- comment
| multiLineComment
multiLineComment = ";;" (~";" any)* ";;"
indent = "⇨"
dedent = "⇦"
}
- Strong and Static typing
- Scripting language
- (Some) Inferred typing
- Multiple return values
- Static scoping
- Sum Typing
- string
- boolean
- number
- list (homogenous)
- any
- void
- error
Constants must start with uppercase letters followed by uppercase letters, numbers, and underscores.
Variables must start with a lowercase letter or underscore and can be followed by both lower and upper case letters, numbers, and underscores.
; Examples of constants
HELLO2018 := 'jen'
LULU_LEMON := true
; Examples of variables
jen3at0r := 'pho'
jenErator = 'ramen'
_JeN_01 := 'udon'
; Will crash at compile time
1dog := 'corgi'
$myFortune := 2
Kbbq := {'Budnamu': 14.99, 'Road-to-seoul': 22.99}
jen allows the user to create custom union types.
; The type "stringOrNumber" can be either a string or number
type stringOrNumber: string | number
Since jen does not have exceptions, there is a built in error type called error. error has two different potential values: ok or err.
; Example of using the err type
result, errorCheck := someFunction()
if errorCheck == err:
print('File could not open')
- Equal ==
- Not equal !=
- Less than <
- Greater than >
- Less than or equal <=
- Greater than or equal >=
- Add +
- Subtract -
- Divide /
- Integer Divide //
- Modulus %
- DivMod /%
- Multiply *
- Postfix increment x++
- Postfix decrement x--
- And &&
- Or ||
- Not !
- XOR &!&
In jen, variables must be declared using the := syntax. Without using this first, jen will error out at compile time. For variable reassignment, jen requires the = syntax. jen also allows parallel declaration and assignment as well.
; Variable initialization/declaration with inferred typing
x := 1
; Reassigning declared variables
x = 2
; Will crash due to type conflict
x = 'hello'
; Parallel declaration
a, b := "eats", "pants"
; Parallel assignment
a, b = "smol", "puppers"
; Declares the function isOdd with type annotation and function signature
isOdd: number -> boolean
isOdd(x):
return x % 2 != 0
; An example of how to write a ternary
x := 1 > 2 ? 'one is greater' : 'two is greater'
x := 4
if x <= 3:
print('Less than or equal to 3 ')
else if x >= 5:
print('Greater than or equal to 5')
else:
print('In between 3 and 5')
iterable = [1, 2, 3, 4]
; Will print out the values in iterable
for i in iterable:
print(i)
i := true
; Classic infinite loop example
while i:
print(i)
; This is a single line comment
;;
This is a multiple line comment.
;;
jen code is located on top, and the corresponding python code is right below it!
add: number, number -> number
add (a, b):
return a + b
def add(a, b):
return a + b
fib: number -> number
fib(num):
if num <= 1:
return 1
return fib(num - 1) + fib(num - 2)
def fib(num):
if num <= 1:
return 1
return fib(num - 1) + fib(num - 2)
areaOfCircle: number -> number
areaOfCircle(radius):
PI = pi()
return PI * radius ^ 2
def areaOfCircle(radius):
return math.pi * radius ** 2
type id: string | number
LIST_OF_EMPLOYEES := [1, 2, "thomas", "elizabeth", 5]
printEmployees: List id -> void
printEmployees(employeeList):
for employeeId in employeeList:
print(employeeId)
LIST_OF_EMPLOYEES = [1, 2, "thomas", "elizabeth", 5]
def printEmployees(employeeList):
for employeeId in employeeList:
print(employeeId)
checkIfBothPositive: number, number -> boolean, boolean
checkIfBothPositive(x, y):
return x >= 0, y >= 0
def checkIfBothPositive(x, y):
return (x >= 0, y >= 0)
- Record Types
- Downcasting for sums
- jen is a nodeJS based transpiler and as such, expects that you have the latest version of nodeJS installed, AND an installation of Python3.
- Clone our repository and run
npm installfirst and foremost. ./node jen.js -a <filename>writes out the AST and stops./node jen.js -i <filename>writes the decorated AST then stops./node jen.js <filename>compiles the jen program to Python3, writing the generated Python code to standard output.- For
npm testto run, as of now jen expects Python3 to be aliased aspythonin your commandline.
- We now have a syntax highlighter for atom in the works! You may try it out by downloading the package manually here.
- Anthony Keba
- Elizabeth Shen
- Jen Shin
- Justin Torres
- Thomas O'Brien
- Tyler Edmiston
- Ray Toal