Hacker News | Any Python users willing to some feedback on some language ideas I had? Thanks

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	Any Python users willing to some feedback on some language ideas I had? Thanks (github.com)
	5 points by pwmanagerdied 109 days ago \| 3 comments

2 points by makecheck 109 days ago | link

I'm not sure the block syntax buys as much as you'd want it to. Maybe a more complex example would help?

For instance, you can create similar syntax with a class definition. I've tossed together something quick below to emulate your UI library (not really something I've tried in practice, but the idea is there):

    class ExampleLabel:
        caption = "This is an example"
        position = (50, 50)

    class ClickMeButton:
        caption = "Click me! Click me!"
        on_click = lambda: sys.stdout.write("The button was clicked.\n")

    class HelloWorldWindow:
        caption = "Hello World"
        dimensions = (400, 300)
        contains = (ExampleLabel, ClickMeButton)

If you then had classes or functions with kwargs arguments, that recognized key names such as "caption", "on_click", etc., then the above classes could be used in this way to instantiate things (either alone, or within something like a Window):

    b = Button(**ClickMeButton.__dict__)
    l = Label(**ExampleLabel.__dict__)

...or equivalently, on the fly:

    l = Label(caption="Other label", position=(10, 20))

Notice that since everything is defined as a class, instantiating duplicates is actually taken care of. For example:

    w1 = Window(**HelloWorldWindow.__dict__)
    w2 = Window(**HelloWorldWindow.__dict__)

Since I haven't "inlined" anything in a block assignment, the definition can be used repeatedly (when put in a class).

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1 point by pwmanagerdied 109 days ago | link

Trying again: With this, it would be possible for a user to create a switch/case statement of their own.

    n = 3
    
    switch n:
        case 1:
            print("n is one")
        case 2:
            print("n is two")
        default:
            print("n is neither one or two")

by injecting "case" into the namespace of a block in "switch", we'd only have to add one identifier to the global namespace. Here's what some of the implementation code might look like.

    @macro
    def switch(value):
        @macro
        def _switch(block):
            cases = dict()            

            def line_callback(value):
                if isinstance(value, SwitchCase):
                    cases[SwitchCase.value] = SwithCase.block
                elif isinstance(value, DefaultCase):
                    default = DefaultCase.block
            
            block(line_callback=line_callback)
            
            try:
                result_block = cases[value]
            except KeyError:
                result_block = default
             
            return(result_block())

        return(_switch)

I wasn't thinking of it exclusively as a data structure tool, but also possibly as a way to create your own flow control operations and such.

This might not be the most compelling possible example in the world, but I hope it helps.

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1 point by pwmanagerdied 109 days ago | link

Thank you very much for the feedback.

I tried to keep the examples simple so that the functionality was clear, I'll try to come up with a more concrete example to demonstrate it's utility.

I'm aware that you can achieve a a lot of already using classes (and metaclasses), but I thought a clearer syntax would be helpful. I don't seeing my code cluttered with "class" when that's not what's actually happening, but of course that could be exactly what was happening in my example.

One thing I originally had in my example (though I decided it wasn't a good idea so I removed it) was

    ui.on_event "click", "altclick":
        print("I've been clicked!")

where on_event macro takes the paren-less tuple of event names and returns another macro which takes the block, then does the correct assignment.

I realize this also isn't a strong example, but it's a little bit more than I have in the post.

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