Advanced function arguments

[differentmatt]

Default arguments
Keyword arguments
Arbitrary argument lists
Unpacking argument lists

https://docs.python.org/3.4/tutorial/controlflow.html#more-on-defining-functions

This may need to be broken up into separate pieces. Please feel free to take on a subset of this work instead of the whole enchilada.

[differentmatt]

Tentative plan:

1. Modify function calls - For calls to user functions and runtime library functions, convert all parameters to a single parameters object that JavaScript can handle, such as {formals:[], keywords:{}}.
2. Modify function definitions - For all user function and library function definitions, move parameter variables to function body, and function body to internal iife.

What does this get us?

• Our original Python parameters have been converted to something JavaScript understands.
• We can process the parameters in the function definition, while maintaining the original function's body (scope and code).

The example below doesn't include unpacking argument lists, but we can imagine passing a similar object containing the correct parameters.

Python input:

def foo(voltage, amps='a', charge='high', *args, **keywords):
  print('voltage', voltage)
  print('amps', amps)
  print('charge', charge)
  print('args', [a for a in args])
  print('keywords', [(k, keywords[k]) for k in keywords])
  print('')

foo(3)
foo(amps=4, voltage=7)
foo(1, 2, 3, 4, 5, 6, p="hi", q='boo')

JavaScript output:

// print() is in runtime library, included here for completeness
function print() {
  var s = '';
  for (var i = 0; i < arguments.length; i++)
    s += arguments[i] + ' ';
  console.log(s);
}

function foo() {
  var _p = arguments[0];
  var _fi = 0;
  var voltage;
  if (_fi < _p.formals.length) {
    voltage = _p.formals[_fi];
    _fi++;
  } else if ('voltage' in _p.keywords) {
    voltage = _p.keywords['voltage'];
    delete _p.keywords['voltage'];
  }
  var amps = 'a';
  if (_fi < _p.formals.length) {
    amps = _p.formals[_fi];
    _fi++;
  } else if ('amps' in _p.keywords) {
    amps = _p.keywords['amps'];
    delete _p.keywords['amps'];
  }
  var charge = 'high';
  if (_fi < _p.formals.length) {
    charge = _p.formals[_fi];
    _fi++;
  } else if ('charge' in _p.keywords) {
    charge = _p.keywords['charge'];
    delete _p.keywords['charge'];
  }
  var args = [];
  while (_fi < _p.formals.length) {
    args.push(_p.formals[_fi]);
    _fi++;
  }
  var keywords = _p.keywords;

  return (function() {
    print('voltage', voltage)
    print('amps', amps)
    print('charge', charge)
    print('args', args)
    var kws = '{'
    for (var k in keywords) {
      kws += k + ":" + keywords[k] + " ";
    }
    kws += '}';
    print('keywords', kws)
    print('')
  })();
}

foo({formals:[3], keywords:{}});
foo({formals:[], keywords:{amps:4, voltage:7}})
foo({formals:[1, 2, 3, 4, 5, 6], keywords:{p:"hi", q:'boo'}})

[differentmatt]

Closing this uber-issue, and will open separate ones for remaining work.

Example for user-defined functions:

def foo(voltage, amps='a', charge='high', *args, **keywords):
  print('voltage', voltage)
  print('amps', amps)
  print('charge', charge)
  print('args length', len(args))
  print('keywords length', keywords.length)
  print('')

foo(3)
foo(amps=4, voltage=7)
foo(1, 2, 3, 4, 5, 6, p="hi", q='boo')

function foo() {
    var __params0 = arguments.length === 1 && arguments[0].formals && arguments[0].keywords ? arguments[0] : null;
    var __formalsIndex0 = 0;
    var __args0 = arguments;
    function __getParam0(v, d) {
        var r = d;
        if (__params0) {
            if (__formalsIndex0 < __params0.formals.length) {
                r = __params0.formals[__formalsIndex0++];
            } else if (v in __params0.keywords) {
                r = __params0.keywords[v];
                delete __params0.keywords[v];
            }
        } else if (__formalsIndex0 < __args0.length) {
            r = __args0[__formalsIndex0++];
        }
        return r;
    }
    var voltage = __getParam0('voltage');
    var amps = __getParam0('amps', 'a');
    var charge = __getParam0('charge', 'high');
    var args = [];
    var keywords = {};
    if (__params0) {
        while (__formalsIndex0 < __params0.formals.length) {
            args.push(__params0.formals[__formalsIndex0++]);
        }
        keywords = __params0.keywords;
    } else {
        while (__formalsIndex0 < __args0.length) {
            args.push(__args0[__formalsIndex0++]);
        }
    }
    return function () {
        __pythonRuntime.functions.print('voltage', voltage);
        __pythonRuntime.functions.print('amps', amps);
        __pythonRuntime.functions.print('charge', charge);
        __pythonRuntime.functions.print('args length', __pythonRuntime.functions.len(args));
        __pythonRuntime.functions.print('keywords length', keywords.length);
        __pythonRuntime.functions.print('');
    }.call(this);
}
foo(__pythonRuntime.utils.createParamsObj(3));
foo(__pythonRuntime.utils.createParamsObj({
    amps: 4,
    __kwp: true
}, {
    voltage: 7,
    __kwp: true
}));
foo(__pythonRuntime.utils.createParamsObj(1, 2, 3, 4, 5, 6, {
    p: 'hi',
    __kwp: true
}, {
    q: 'boo',
    __kwp: true
}));