mirror of
https://github.com/idris-lang/Idris2.git
synced 2024-12-22 03:01:31 +03:00
62 lines
2.7 KiB
ReStructuredText
62 lines
2.7 KiB
ReStructuredText
**************************
|
|
Frequently Asked Questions
|
|
**************************
|
|
|
|
Can Idris 2 compile itself?
|
|
===========================
|
|
|
|
Yes, Idris 2 is implemented in Idris 2. By default, it targets
|
|
`Chez Scheme <https://cisco.github.io/ChezScheme/>`_, so you can bootstrap
|
|
from the generated Scheme code, as described in Section :ref:`sect-starting`.
|
|
|
|
Why does Idris 2 target Scheme? Surely a dynamically typed target language is going to be slow?
|
|
===============================================================================================
|
|
|
|
You may be surprised at how fast Chez Scheme is :). `Racket <https://download.racket-lang.org/>`_,
|
|
as an alternative target, also performs well. Both perform better than the
|
|
Idris 1 back end, which is written in C but has not had the decades of
|
|
engineering effort by run time system specialists that Chez and Racket have.
|
|
Chez Scheme also allows us to turn off run time checks, which we do.
|
|
|
|
As anecdotal evidence of the performance improvement, as of 23rd May 2020, on a
|
|
Dell XPS 13 running Ubuntu, the performance is:
|
|
|
|
* Idris 2 (with the Chez Scheme runtime) checks its own source in 93 seconds.
|
|
* The bootstrapping Idris 2 (compiled with Idris 1) checks the same source in 125s.
|
|
* Idris 1 checks the bootstrapping Idris 2's source (the same as the above,
|
|
but with minor variations due to the syntax changes) in 768 seconds.
|
|
|
|
This is, nevertheless, not intended to be a long term solution, even if it
|
|
is a very convenient way to bootstrap.
|
|
|
|
Can Idris 2 generate Javascript? What about plug-in code generators?
|
|
====================================================================
|
|
|
|
Not yet, but there is a Javascript code generator in development.
|
|
|
|
Like Idris 1, Idris 2 will support plug-in code generation to allow you to
|
|
write a back end for the platform of your choice, but this is not yet
|
|
implemented.
|
|
|
|
What are the main differences between Idris 1 and Idris 2?
|
|
==========================================================
|
|
|
|
The most important difference is that Idris 2 explicitly represents *erasure*
|
|
in types, so that you can see at compile time which function and data type
|
|
arguments are erased, and which will be present at run time. You can see more
|
|
details in :ref:`sect-multiplicities`.
|
|
|
|
Idris 2 has significantly better type checking performance (perhaps even an
|
|
order of magnitude!) and generates significantly better code.
|
|
|
|
Also, being implemented in Idris, we've been able to take advantage of the
|
|
type system to remove some significant sources of bugs!
|
|
|
|
You can find more details in Section :ref:`updates-index`.
|
|
|
|
Where can I find more answers?
|
|
==============================
|
|
|
|
The `Idris 1 FAQ <https://docs.idris-lang.org/en/latest/faq/faq.html>`_ is
|
|
mostly still relevant.
|