Mass

Simple language, interpreter written in C#.

Work in Progress

Design Notes

Mass takes few key ideas from different languages.

• Interpreted Language
• No typed variables
• Local variable declaration
• Ruby syntax, but with explicit use of parentheses to call functions
• 'define' for function definition
• 'function' for anonymous functions
• End of line as command separation
• Explicit 'end' to close block statements
• Functions as first class citizens
• require('module') a la Node.js
• Dynamic objects, as in Javascript or Python. You can assign any property at any time
• No ; to separate commands nor { } to group statements
• Access to underlying classes and objects (.NET class libraries)

Development

git clone git://github.com/ajlopez/Mass.git
cd Mass
git submodule init
git submodule update

Expressions

Constants

"foo"
123

Dynamic object

adam = { name = "Adam", age = 800 }
empty = {}

Array

numbers = [ 1, 2, 3 ]
empty = []

The expression can be continued in other line, after [, {, ,

numbers = [ 
	1,
	2,
	3
	]
	
adam = {
	name = "Adam",
	age = 800
}

Simple arithmetic

a+b
12*a
a/b
a/(1+b)

The operators +, -, *, / are supported.

function expression

foo = function(a,b)
	a+b
end

Variable scope

A variable set in file, has file scope:

a = 1

A variable with file scope, can be accessed from functions defined in the same file

a = 1

define foo()
	a+1
end

foo() # returns 2

If a variable is declared in a function, it will have function scope

a = 1

define foo()
	a = 2
end

foo() # returns 2
a # it is 2

Instead

a = 1

define foo()
    var a
	a = 2
end

foo() # returns 2
a # it is still 1

Commands

assignment

a = 123
b = "foo"
dog = {}
dog["name"] = "Nero"
numbers = [1, 2, 3]
numbers[0] = 0

if

if <expr>
	<command>
	...
[else
	<command>
	...
]
end

define

define <name>([<name>, ... ])
	<command>
	...
end

for each

for <name> in <expr>
	<command>
	...
end

for

for <name> = <expr> to <expr> [step <expr>]
	<command>
	...
end

while

while <expr>
	<command>
	...
end

continue and break for for and while

while <expr>
	...
	continue
	...
end

for ...
	...
	break
	...
end

class and new

class Dog
	define initialize(name)
		self.name = name
	end
	
	define sayhello()
		println("warf!")
	end
end

nero = new Dog("Nero")

subclass and call super initialize

class Rectangle
	define initialize(width, height)
		self.width = width
		self.height = height
	end
	
	define area()
		self.width * self.height
	end
end

class Square extends Rectangle
	define initialize(side)
		super(side, side)
	end
end

line comments with #

# this is a comment
a = 1 # a simple assignment

Predefined variables

The global variable is special: it's the only variable that is not a local one. It points to root context.

# global variable
global.a = 1

# file local variable
a = 3

define foo()
	# set global variable
	global.a = 2
	
	# create and set local variable with function scope
	# you cannot change a file variable value from function scope
    var a
	a = 4
end

define bar()
	# get file local variable value
	a
end

foo() # == 4
bar() # == 3

Predefined functions

print and println

println("Hello, world")
println("Hello", "world") # output: two lines

print("Hello, ")
println("world")

Require

To import a module

mymodule = require("mymodule")

Variants

mymodule = require("mymodule.ms")
mymodule = require("./mymodule")
mymodule = require("/libs/mymodule")

A module is a .ms file, executed in its own context. The value returned by require function is the value returned by module code. If no explicit return, the value of the last command is returned

Example:

define add(a, b)
	a+b
end

{
	one = 1,
	two = 2,
	three = 3,
	foo = add
}

The return value is an object containing one, two, three and foo, the last one pointing to internal defined function add

The lookup module algorithm:

• If the name has an absolute path, search only in that path
• Search in current file directory
• If file exists with extensions .ms, that file is loaded
• If directory exists named as the module, the file init.ms in that directory is loaded
• If file does not exists, the same search is repeated in modules subdirectory in current file directory
• If file does not exists, the search is repeated at modules subdirectory in parent directory, and so on, up to top directory
• If file does not exists, the search is repeated in node_modules subdirectory in current file directory
• If file does not exists, the search is repeated at node_modules subdirectory in parent directory, and so on, up to top directory
• If the file is not found, search in current executing assembly directory instead of current file directory

Samples

Hello world

println("Hello, world")

For each

for k in [1,2,3,4,5,6]
	println(k)
end

For

for k = 1 to 6
	println(k)
end

for k = 1 to 6 step 2
	println(k)
end

Simple function

define add(a, b)
	a+b
end

A function returns the value of the last command

You can use a return command

define add(a, b)
	return a+b
end

Current directory files, using native object

dirinfo = new System.IO.DirectoryInfo(".")

for fileinfo in dirinfo.GetFiles()
	println(fileinfo.Name)
end

Run

The executable mass.exe is the interpreter (compiled in Mass.Console project)

mass <file> [<file> ... ]

To be done

• Exceptions with try/catch
• Object definition
• Real numbers
• Characters
• REPL

References

• Expression as a Compiler
• Dynamic LINQ (Part 1: Using the LINQ Dynamic Query Library)
• The binary operator Multiply is not defined for the types 'System.Int32' and 'System.Double'.

Origin of Name

Mass language is dedicated to @MArtinSaliaS