[Python-ideas] How do you think about these language extensions?

[David Mertz]

This is pretty easy to write without any syntax changes, just using a
higher-order function `compose()` (possible implementation at foot).
Again, I'll assume auto-currying like the map/filter versions of those
functions in toolz, as Steven does:


> result = (myfile.readlines()
>           -> map(str.strip)
>           -> filter( lambda s: not s.startwith('#') )
>           -> sorted
>           -> collapse  # collapse runs of identical lines
>           -> extract_dates
>           -> map(date_to_seconds)
>           -> min
>           )
>

result = compose(map(str.strip),
                 filter(lambda s: not startswith('#'),
                 sorted,
                 collapse,
                 extract_dates,
                 map(date_to_seconds),
                 min
                 )(myfile.readlines())

Pretty much exactly the same thing with just a utility HOF.  There's one
that behaves right in `toolz`/`cytoolz`, or I've used this one in some
publications and teaching material:

def compose(*funcs):
    """Return a new function s.t.
       compose(f,g,...)(x) == f(g(...(x)))
    """
    def inner(data, funcs=funcs):
        result = data
        for f in reversed(funcs):
            result = f(result)
        return result
    return inner

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