Comment by quotemstr

Comment by quotemstr 10 months ago

It's not even a subset. They break foundational contracts of the Python language without technical necessity. For example,

> Dictionaries: Codon's dictionary type does not preserve insertion order, unlike Python's as of 3.6.

That's a gratuitous break. Nothing about preserving insertion order interferes with compilation, AOT or otherwise. The authors of Codon broke dict ordering because they felt like it, not because they had to.

At least Mojo merely claims to be Python-like. Unlike Codon, it doesn't claim to be Python then note in the fine print that it doesn't uphold Python contractual language semantics.

orf 10 months ago

Try not to throw around statements like “they broke duct ordering because they felt like it”.

Obviously they didn’t do that. There are trade-offs when preserving dictionary ordering.

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baq 10 months ago

dicts ordering keys in insertion order isn't an implementation detail anymore and hasn't been for years.

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- nick238 10 months ago
  
  I get that all dicts are now effectively an `collections.OrderedDict`, but I've never seen practical code that uses the insertion order. You can't do much with that info (no `.pop()`, can't sort a dict without recreating it) beyond maybe helping readability when you print or serialize it.
  
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  funny_falcon 10 months ago
  
  Readability, reproducibility, and simple LRU.
  Reproducibility matters for tests, they become simpler. Some other algorithms become simpler as well.
  LRU is just a dict with preserving order: on access just delete and insert again.
  
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dathinab 10 months ago

if you claim
> high-performance Python implementation
then no this aren't trade-offs but breaking the standard without it truly being necessary
most important this will break code in a subtle and potentially very surprising way
they could just claim they are python like and then no one would hold them for not keeping to the standard
but if you are misleading about your product people will find offense even if it isn't intentionally

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actionfromafar 10 months ago

The trade-off is a bit of speed.

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- cjbillington 10 months ago
  
  This might be what you meant, but the ordered dicts are faster, no? I believe ordering was initially an implementation detail that arose as part of performance optimisations, and only later declared officially part of the spec.
  
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  Someone 10 months ago
  
  > but the ordered dicts are faster, no?
  They may be in the current implementations, but removing an implementation constraint can only increase the solution space, so it cannot make the best implementation slower.
  As a trivial example, the current implementation that guarantees iteration happens in insertion order also is a valid implementation for a spec that does not require that guarantee.
  
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adammarples 10 months ago

Well would you claim that Python 3.5 isn't python?

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stoperaticless 10 months ago

All versions of python are python.
If lang is not compatible with any of python versions, then the lang isn’t python.
False advertising is not nice. (even if the fineprint clarifies)

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- thesz 10 months ago
  
  > If lang is not compatible with any of python versions, then the lang isn’t python.
  Python versions are not compatible between themselves, as python does not preserve backward compatibility, ergo python is not python.
  
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  KeplerBoy 10 months ago
  
  The words "any" and "all" have a different meaning.
  
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  skeledrew 10 months ago
  
  Interestingly I recently had to run a script I wrote for 3.11 on an old system that has 3.6, and the only thing I had to remove were a few type hints (which of course don't affect function). Seems pretty backwards compatible to me.
  
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  stoperaticless 9 months ago
  
  Pretty compatible != compatible.
  (I can edit my own script, I would hate if installation instructions for “django” would include “just remove the type hints from the scripts”)
  
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