ykst / funlang

a tiny scripting language

funlang

A tiny language with following features:

• lexical closure
• gabage collection (simple mark and sweep)
• custom infix operator
• eval
• exec (!!)

Build

You need GHC to build.

$ make

Please fix other external dependencies manually if required.

Syntax (EBNF + Regular expression)

Program ::= {Statement "\n"}

Statement ::= 
 	  FunctionDef
	| InfixDef
 	| VariableDef
 	| IfBlock
 	| WhileBlock
 	| Return
 	| Assign
 	| CallAccess

Function ::= 
	"fun" "(" Varlist ")" "\n" 
 			Program
	End

End ::= /\\_+/

Varlist ::= epsilon | Id {"," Id}

Id ::= /[a-zA-Z][0-9a-zA-Z]*/

InfixDef ::= 
	InfixSpec "(" Id InfixOp Id ")" "\n" 
 		Program
	End

InfixSpec ::= 
	  /infixL[0-9]+/
	| /infixR[0-9]+/

InfixOp ::= /[!$%&<>?_*:;@/\\=|\-+.]+/

VariableDef ::= 
	"var" Id ["=" Expr]

IfBlock ::=
	"if" Expr "\n"
		Program
	{"elsif" Expr "\n"
		Program}
	["else" "\n"
		Program]
	End

WhileBlock ::= 
	"while" Expr "\n"
		Program
	End

Return ::= 
	"return" Expr

Assign ::= 
	Id "=" Expr

CallAccess ::=
	{Call "." | Id "."} Call

Call ::= 
	Method "(" Varlist ")"

Method ::= /\$?[a-zA-Z][0-9a-zA-Z]*/

Expr ::= 
	  Expr BinOp Expr 
	| UniOp Expr 
	| "(" Expr ")"
	| Terminal

Terminal ::= 
	  Call 
	| Instantiate
	| StringLiteral
	| IntLiteral
	| BoolLiteral

Instantiate ::= 
	Id "{" Varlist "}"

StringLiteral ::= ? C-like string literal ?

IntLiteral ::= /[1-9][0-9]*/

BoolLiteral ::= "true" | "false"

###Intrinsics

Every intrinsic functions are started by $. Our Helloworld is,

$print("Hello World\n")

Other supported intrinsics are:

• $eval(str) ... eval string.

• $gc() ... run gabage collection immediately.

• $exec(str) ... execute external command and get stdout string as return value.

• $error(str) ... throw an error. anyway, catch is not implemented :p

Usage

The standalone binary (bin/fun) supports REPL by haskeline. Just run the binary without arguments.

$ bin/fun
> 1 + 1
2
> $print("Hello World!\n")
Hello World!
> :q
$

Following interpretor commands are supported:

• :q ... c quit REPL.

• :l <filename> ... load a script file.

• :c ... initialize the runtime environment.

• :h ... help.

To execute a script file, pass the filepath to the binary.

$ bin/fun hello.fun

So what's all about?

Just for fun :)