brainstorming promise syntax

promises-roundup.js

// a few ideas for unifying async "promises"

// there are three types of callbacks:
function callback( data ){ sys.puts( "called on both success and error" ) }
function success( data ){ sys.puts( "called on success only" ) }
function error( data ){ sys.puts( "called on error only" ) }

// for any async function, offer a single optional callback.
posix.cat( "config.json", callback );

// the callback can be omitted in the style of partial application,
// to allow returning a promise that takes either one callback,
posix.cat( "config.json" )( callback );

// or takes a success callback and error callback. this is nice because the index
// of each callback is analogous to its UNIX exit code:
posix.cat( "config.json" )( success, error );

// to keep code readable, inline functions should be named:
posix.cat( "config.json" )(
  function success(){ ... },
  function error(){ ... }
);

// the promise itself would be chained to allow multiple callbacks
posix.cat( "config.json" )
  ( callback )
  ( callback )
  ( success, error );