5e94a906cd
Compile a `for[*]/list` form to behave more like `map` by `cons`ing
onto a recursive call, instead of accumulating a list to reverse.
This style of compilation requires a different strategy than before.
A form like
(for*/fold ([v 0]) ([i (in-range M)]
[j (in-range N)])
j)
compiles as nested loops, like
(let i-loop ([v 0] [i 0])
(if (unsafe-fx< i M)
(i-loop (let j-loop ([v v] [j 0])
(if (unsafe-fx< j N)
(j-loop (SEL v j) (unsafe-fx+ j 1))
v))
(unsafe-fx+ i 1))
v))
instead of mutually recursive loops, like
(let i-loop ([v 0] [i 0])
(if (unsafe-fx< i M)
(let j-loop ([v v] [j 0])
(if (unsafe-fx< j N)
(j-loop (SEL v j) (unsafe-fx+ j 1))
(i-loop v (unsafe-fx+ i 1))))
v))
The former runs slightly faster. It's difficult to say why, for
certain, but the reason may be that the JIT can generate more direct
jumps for self-recursion than mutual recursion. (In the case of mutual
recursion, the JIT has to generate one function or the other to get a
known address to jump to.)
Nested loops con't work for `for/list`, though, since each `cons`
needs to be wrapped around the whole continuation of the computation.
So, the `for` compiler adapts, depending on the initial form. (With a
base, CPS-like approach to support `for/list`, it's easy to use the
nested mode when it works by just not fully CPSing.)
Forms that use `#:break` or `#:final` use the mutual-recursion
approach, because `#:break` and #:final` are easier and faster that
way. Internallt, that simplies the imoplementation. Externally, a
`for` loop with `#:break` or `#:final` can be slightly faster than
before.
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| appveyor.yml | ||
| INSTALL.txt | ||
| Makefile | ||
| README.md | ||
This is the source code for the core of Racket. See "INSTALL.txt" for full information on building Racket.
To build the full Racket distribution from this repository, run make
in the top-level directory. To build the Minimal Racket, run make base.
The rest of the Racket distribution source code is in other repositories under the Racket GitHub organization.
Contribute to Racket by submitting a pull request, joining the development mailing list, or visiting the IRC channel.
License
Racket Copyright (c) 2010-2016 PLT Design Inc.
Racket is distributed under the GNU Lesser General Public License (LGPL). This implies that you may link Racket into proprietary applications, provided you follow the rules stated in the LGPL. You can also modify Racket; if you distribute a modified version, you must distribute it under the terms of the LGPL, which in particular states that you must release the source code for the modified software.
See racket/src/COPYING_LESSER.txt for more information.