mirror of https://github.com/exaloop/codon.git
54 lines
2.0 KiB
Markdown
54 lines
2.0 KiB
Markdown
While Codon's syntax and semantics are nearly identical
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to Python's, there are some notable differences that are
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worth mentioning. Most of these design decisions were made
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with the trade-off between performance and Python compatibility
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in mind.
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Please see our [roadmap](roadmap.md) for more information about
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how we plan to close some of these gaps in the future.
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# Data types
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- **Integers:** Codon's `int` is a 64-bit signed integer,
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whereas Python's (after version 3) can be arbitrarily large.
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However Codon does support larger integers via `Int[N]` where
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`N` is the bit width.
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- **Strings:** Codon currently uses ASCII strings unlike
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Python's unicode strings.
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- **Dictionaries:** Codon's dictionary type does not preserve
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insertion order, unlike Python's as of 3.6.
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- **Tuples**: Since tuples compile down to structs, tuple lengths
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must be known at compile time, meaning you can't convert an
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arbitrarily-sized list to a tuple, for instance.
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# Type checking
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Since Codon performs static type checking ahead of time, a
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few of Python's dynamic features are disallowed. For example,
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monkey patching classes at runtime (although Codon supports a
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form of this at compile time) or adding objects of different
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types to a collection.
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These few restrictions are ultimately what allow Codon to
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compile to native code without any runtime performance overhead.
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Future versions of Codon will lift some of these restrictions
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by the introduction of e.g. implicit union types.
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# Numerics
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For performance reasons, some numeric operations use C semantics
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rather than Python semantics. This includes, for example, raising
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an exception when dividing by zero, or other checks done by `math`
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functions. Strict adherence to Python semantics can be achieved by
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using the `-numerics=py` flag of the Codon compiler. Note that this
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does *not* change `int`s from 64-bit.
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# Modules
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While most of the commonly used builtin modules have Codon-native
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implementations, a few are not yet implemented. However these can
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still be used within Codon via `from python import`.
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