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Diffstat (limited to 'Doc/howto/functional.rst')
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diff --git a/Doc/howto/functional.rst b/Doc/howto/functional.rst index 21272fa..1557f55 100644 --- a/Doc/howto/functional.rst +++ b/Doc/howto/functional.rst @@ -3,12 +3,10 @@ ******************************** :Author: \A. M. Kuchling -:Release: 0.30 +:Release: 0.31 (This is a first draft. Please send comments/error reports/suggestions to -amk@amk.ca. This URL is probably not going to be the final location of the -document, so be careful about linking to it -- you may want to add a -disclaimer.) +amk@amk.ca.) In this document, we'll take a tour of Python's features suitable for implementing programs in a functional style. After an introduction to the @@ -49,17 +47,19 @@ Programming languages support decomposing problems in several different ways: functional languages include the ML family (Standard ML, OCaml, and other variants) and Haskell. -The designers of some computer languages have chosen one approach to programming -that's emphasized. This often makes it difficult to write programs that use a -different approach. Other languages are multi-paradigm languages that support -several different approaches. Lisp, C++, and Python are multi-paradigm; you can -write programs or libraries that are largely procedural, object-oriented, or -functional in all of these languages. In a large program, different sections -might be written using different approaches; the GUI might be object-oriented -while the processing logic is procedural or functional, for example. +The designers of some computer languages choose to emphasize one +particular approach to programming. This often makes it difficult to +write programs that use a different approach. Other languages are +multi-paradigm languages that support several different approaches. +Lisp, C++, and Python are multi-paradigm; you can write programs or +libraries that are largely procedural, object-oriented, or functional +in all of these languages. In a large program, different sections +might be written using different approaches; the GUI might be +object-oriented while the processing logic is procedural or +functional, for example. In a functional program, input flows through a set of functions. Each function -operates on its input and produces some output. Functional style frowns upon +operates on its input and produces some output. Functional style discourages functions with side effects that modify internal state or make other changes that aren't visible in the function's return value. Functions that have no side effects at all are called **purely functional**. Avoiding side effects means @@ -616,7 +616,7 @@ Built-in functions Let's look in more detail at built-in functions often used with iterators. -Two Python's built-in functions, :func:`map` and :func:`filter`, are somewhat +Two of Python's built-in functions, :func:`map` and :func:`filter`, are somewhat obsolete; they duplicate the features of list comprehensions but return actual lists instead of iterators. @@ -842,8 +842,8 @@ Fredrik Lundh once suggested the following set of rules for refactoring uses of 4) Convert the lambda to a def statement, using that name. 5) Remove the comment. -I really like these rules, but you're free to disagree that this lambda-free -style is better. +I really like these rules, but you're free to disagree +about whether this lambda-free style is better. The itertools module |