Aggregate pattern: Difference between revisions

Revision as of 08:58, 29 December 2007

Latest revision as of 02:53, 12 February 2025

(18 intermediate revisions by 15 users not shown)

Line 1:

{{Short description|Concepts in statistics and computer science}}

{{split}}

{{one source |date=March 2024}}

An '''Aggregate pattern''' can refer to concepts in either statistics or computer programming. Both uses dealsimplify withcomplexity considering a large case as composed ofinto smaller, simpler, piecesparts.

== Statistics ==

An aggregate pattern is an important statistical concept in many fields that rely on [[statistics]] to predict the behavior of large groups, based on the tendencies of subgroups to consistently behave in a certain way. It is particularly useful in [[sociology]], [[economics]], [[psychology]], and [[criminology]].

== Computer programming ==

In ''[[Design Patterns]]'', an aggregate is not a [[Software design pattern|design pattern]] but rather refers to an object such as a list, vector, or generator which provides an interface for creating [[iterator]]s. The following example code is in [[Python (programming language)|Python]].

{{Expand-section|a clear explanation of the code example or adding another code example|date=October 2007}}

<syntaxhighlight lang="python">

def fibonacci(n: int):

In [[Design Patterns]], an aggregate is not a design pattern but rather refers to an object such as a list, vector, or generator which provides an interface for creating [[iterator]]s. The following example code is in [[Python (programming language)|Python]].

a, b = 0, 1

<pre>

count += 10

mylist = ['apples','oranges','milk','eggs','flour']

while count < n:

count += 01

for item in mylist:

print "Mom, we're out of " +a, b = b, itema + "!"b

yield a

def fibonacci(n):

a,b = 0,1

count = 0

while count < n:

count += 1

a,b = b, a+b

yield a

for x in fibonacci(10):

print print(x)

def fibsum(n: int) -> int:

total = 0

for x in fibonacci(n):

total += x

return total

def fibsum_alt(n: int) -> int:

"""

" Alternate implementation. demonstration that Python's built-in function sum() works with arbitrary iterators"

return sum(fibonacci(n))

works with arbitrary iterators.

"""

return sum(fibonacci(n))

myNumbers = [1, 7, 4, 3, 22]

def average(g) -> float:

return float(sum(g)) / len(g) #in In Python 3.0 the cast to float willis no longer be necessary

</syntaxhighlight>

Python hides essentially all of the details using the [httphttps://wwwdocs.python.org/doc3/liblibrary/typeiterstdtypes.html#iterator-types iterator protocol]. Confusingly, ''[[Design Patterns]]'' uses "aggregate" to refer to the blank in the code <code>for x in ___:</code> which is unrelated to the term "aggregation" .<ref>[[Design Patterns]], p. 22: "Aggregation implies that one object owns or is responsible for another object. ... Aggregation implies that an aggregate object and its owner have identical lifetimes."</ref>. Neither of these terms refer to the statistical aggregation of data such as the act of adding up the Fibonacci sequence or taking the average of a list of numbers.

</pre>

Python hides essentially all of the details using the [http://www.python.org/doc/lib/typeiter.html iterator protocol]. Confusingly, [[Design Patterns]] uses "aggregate" to refer to the blank in the code <code>for x in ___:</code> which is unrelated to the term "aggregation" <ref>[[Design Patterns]], p. 22: "Aggregation implies that one object owns or is responsible for another object. ... Aggregation implies that an aggregate object and its owner have identical lifetimes.</ref>. Neither of these terms refer to the statistical aggregation of data such as the act of adding up the Fibonacci sequence or taking the average of a list of numbers.

== See also ==

* [[Visitor pattern]]

* [[Template class]]

Line 55 ⟶ 47:

* [[Type safety]]

* [[Functional programming]]

== References ==

{{Reflist}}

[[Category:Software design patterns]]

[[Category:Articles with example PerlPython (programming language) code]]

{{statistics-stub}}