条件计算 [英] conditional computation
问题描述
我想经常使用计算缓存方案，比如
o = CACHECOMPUTE complex-key-expr expensive-calc-expr
而不用编写复杂的密钥-expr或者昂贵的calc-expr两次。
所以它的丑陋：
_ = complex-key-expr; o = cache.get（_）或cache.setdefault（_，expensive-calc-expr）
有什么想法吗？
-robert
I want to use a computation cache scheme like
o = CACHECOMPUTE complex-key-expr expensive-calc-expr
frequently and elegantly without writing complex-key-expr or expensive-calc-expr twice.
So its ugly:
_=complex-key-expr; o=cache.get(_) or cache.setdefault(_,expensive-calc-expr)
Any ideas?
-robert
推荐答案
在星期四26/10/2006 16:30，罗伯特写道：
At Thursday 26/10/2006 16:30, robert wrote:
>我想使用计算缓存方案，例如
o = CACHECOMPUTE complex-key-expr expensive-calc-expr
经常和优雅地没有写复杂的key-expr或
昂贵的calc-expr两次。
所以它的丑陋：
_ = complex-key-expr; o = cache.get（_）或
cache.setdefault（_，expensive-calc-expr）
任何想法？
>I want to use a computation cache scheme like
o = CACHECOMPUTE complex-key-expr expensive-calc-expr
frequently and elegantly without writing complex-key-expr or
expensive-calc-expr twice.
So its ugly:
_=complex-key-expr; o=cache.get(_) or
cache.setdefault(_,expensive-calc-expr)
Any ideas?
memoize模式可以提供帮助;在
http://wiki.python.org/moin/PythonDecoratorLibrary你可以看到使用装饰器的
实现。
-
Gabriel Genellina
Softlab SRL
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The memoize pattern can help; in
http://wiki.python.org/moin/PythonDecoratorLibrary you can see an
implementation using decorators.
--
Gabriel Genellina
Softlab SRL
__________________________________________________
Correo Yahoo!
Espacio para todos tus mensajes, antivirus y antispam ?gratis!
?Abrí tu cuenta ya! - http://correo.yahoo.com.ar
robert写道：
robert wrote:
我想使用像
$这样的计算缓存方案b
$ bo = CACHECOMPUTE complex-key-expr expensive-calc-expr
经常且优雅地没有编写complex-key-expr或expensive-calc-expr两次。 br />
所以它的丑陋：
_ = complex-key-expr; o = cache.get（_）或cache.setdefault（_，expensive-calc-expr）
有什么想法吗？
-robert
I want to use a computation cache scheme like
o = CACHECOMPUTE complex-key-expr expensive-calc-expr
frequently and elegantly without writing complex-key-expr or expensive-calc-expr twice.
So its ugly:
_=complex-key-expr; o=cache.get(_) or cache.setdefault(_,expensive-calc-expr)
Any ideas?
-robert
你的问题有点简洁，所以我的答案可能不适合它，
但听起来你想要的是什么通常称为memoization，
，其中一个函数缓存其昂贵的计算返回值，
其中缓存由函数参数键入。
请参阅：
http://aspn.activestate.com/ASPN/Coo...n/Recipe/52201
以及Cookbook中的各种其他实施细节。
Your question is a bit terse, so my answer might not be spot on for it,
but it sounds like you want what is typically called ''memoization'',
whereby a function caches its expensive-to-calculate return values,
where the cache is keyed by the function arguments.
See:
http://aspn.activestate.com/ASPN/Coo...n/Recipe/52201
and various other implimentations in the Cookbook for details.
Gabriel Genellina写道：
Gabriel Genellina wrote:
在星期四26/10/2006 16:30，罗伯特写道：
At Thursday 26/10/2006 16:30, robert wrote:
>我想使用计算缓存方案，例如
o = CACHECOMPU TE complex-key-expr expensive-calc-expr
频繁而优雅，无需编写复杂的key-expr或
昂贵的calc-expr两次。
所以它的丑陋：
_ = complex-key-expr; o = cache.get（_）或
cache.setdefault（_，expensive-calc-expr）
任何想法？
>I want to use a computation cache scheme like
o = CACHECOMPUTE complex-key-expr expensive-calc-expr
frequently and elegantly without writing complex-key-expr or
expensive-calc-expr twice.
So its ugly:
_=complex-key-expr; o=cache.get(_) or
cache.setdefault(_,expensive-calc-expr)
Any ideas?
memoize模式可以提供帮助;在
http://wiki.python.org/moin/PythonDecoratorLibrary你可以看到使用装饰器的
实现。
The memoize pattern can help; in
http://wiki.python.org/moin/PythonDecoratorLibrary you can see an
implementation using decorators.
谢谢，因此它不会帮助挂钩单行表达式，但它有帮助我记得lambda！ ：耻辱::
类MemoCache（字典）：#cache在会话期间昂贵的对象（仅限内存）
def memo（self，k，f）：
尝试：返回自己[k]
除了IndexError：
返回self.setdefault（k，f（））
cache = MemoCache（）
....
o = cache.memo（complex-key-expr，lambda：expensive-calc-expr）
现在是pythonic。
-robert
thanks, as such it will not help hooking single line expressions, but it helped me remember the lambda ! :shame: :
class MemoCache(dict): # cache expensive Objects during a session (memory only)
def memo(self, k, f):
try: return self[k]
except IndexError:
return self.setdefault(k, f())
cache=MemoCache()
....
o = cache.memo( complex-key-expr, lambda: expensive-calc-expr )
Thats pythonic now.
-robert
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