Vishvas's notes

Distinctive features of the language

Purpose of design

Inspired by functional programming languages.

Distributed computing: There’ll be many services on the internet, need a language to orchestrate them. So, good internet mashup language.

Good for concisely reasoning about distrubted systems.

Sites

Everything is a site: a possibly remote function without side-effect which may not respond. Even +, -, if(..) etc.. are sites. These may return sites too. Actual site call is not executed until all arguments are available.

Functions

The language allows/ needs functions, but they’re not site calls. It is simply a parametrized expression.

Parallelism

Highly parrellelizable.

Even a+b: a and b are evaluated independently.

Speed

Writing, Building and executing code

Run in browser, or using an eclipse plugin.

Debugging

Help

The website.

Pre-compilation processing

Variable and data types

Data types

signal is a unary data-type. boolean, numeric etc.. are other data types.

[] is an empty list.

a = Ref() yields a pointer: then do a.read(), a.write().

Declaration syntax

val valName = expression.

This boils down to pruning operator. Eg: $a | v a l N a m e$ is actually $a | b < b < e x p r e s s i o n$ .

It is scoped to the expression in the next line.

Pattern matching: $a : b = [1, 2, 3]; (_{,} a) = (2, 3)$ .

Data manipulation

Operators

/= is ’not equal to’ boolean operator.

Accessing object methods

channel.get() actually is shorthand for calling a function which retrieves the get() function and then invokes it.

Code structure

Sentence syntax

There is actually just one sentence/ expression. Rest is syntactic sugar. Line breaks don’t matter.

Commenting

{- asdf -}

Combinators

Use to stitch together expressions.

Parallel combinator: $a | b$ .

Sequential/ push combinator: $>$ . Eg: $p r o m p t () > b > c (b)$ . Syntactic sugar: $p r o m p t () > b > c$ is same as $p r o m p t () » c$ .

Pruning/ pull operator: $a < b$ . Both sides begin to be evaluated simultaneously; if LHS needs a value, then it blocks.

Syntax of functions

Can be nested.

def fnName(arglist) = expression.

Function definition which uses pattern matching, usual syntactic sugar to specify termination condition:

fn([]) = asdfasdf

fn((a:asdf)) = asdfasdf

Decision, timing sites

if(). stop() never returns any value. RTimer().

Iteration accomplished through recursion.

Function invocation

fn(arguments) or fn.

fn(expression): syntactic sugar for $f (x) < x < e x p r e s s i o n$ .

Error handling

Other library functions

User interaction I/O sites

prompt(), print().