Civil Rights
Movements, leaders, victories and the continuing fight for equality.
Explore the people, places, events, achievements, struggles and stories that shaped our journey.
Movements, leaders, victories and the continuing fight for equality.
Innovation, patents, science, technology and world-changing contributions.
Pioneers, champions, Negro Leagues, records, activism and excellence.
Meet the people whose lives, choices and achievements shaped the journey.
Black towns, communities, institutions and places where history happened.
Moments that changed communities, movements, institutions and the nation.
Mansa Musa was the ruler of the Mali Empire in West Africa. Details recorded here should be sourced; unknown information is left blank.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
Perl Design Patterns Book is an online textbook about Perl style and design and analysis. The contents are licensed under GNU Free Documentation License.
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Perl Design Patterns Book is an online textbook about Perl style and design and analysis. The contents are licensed under GNU Free Documentation License.
In object-oriented design, the chain-of-responsibility pattern is a behavioral design pattern consisting of a source of command objects and a series of processing objects. Each processing object contains logic that defines the types of command objects that it can handle; the rest are passed to the next processing object in the chain. A mechanism also exists for adding new processing objects to the end of this chain. In a variation of the standard chain-of-responsibility model, some handlers may act as dispatchers, capable of sending commands out in a variety of directions, forming a tree of responsibility. In some cases, this can occur recursively, with processing objects calling higher-up processing objects with commands that attempt to solve some smaller part of the problem; in this case recursion continues until the command is processed, or the entire tree has been explored. An XML interpreter might work in this manner. This pattern promotes the idea of loose coupling. The chain-of-responsibility pattern is structurally nearly identical to the decorator pattern, the difference being that for the decorator, all classes handle the request, while for the chain of responsibility, exactly one of the classes in the chain handles the request. This is a strict definition of the Responsibility concept in the Gang of Four Design Patterns book. However, many implementations (such as loggers below, or UI event handling, or servlet filters in Java, etc.) allow several elements in the chain to take responsibility.
Richard Helm is one of the co-authors (referred to as the "Gang of Four") of the influential Design Patterns book. In 2006 he was awarded the Dahl–Nygaard Prize for his contributions to the state of the art embodied in that book. He received the ACM SIGSOFT Outstanding Research Award in 2010.
Design Patterns: Elements of Reusable Object-Oriented Software (1994) is a software engineering book describing software design patterns. The book was written by Erich Gamma, Richard Helm, Ralph Johnson, and John Vlissides, with a foreword by Grady Booch. The book is divided into two parts, with the first two chapters exploring the capabilities and pitfalls of object-oriented programming, and the remaining chapters describing 23 classic software design patterns. The book includes examples in C++ and Smalltalk. It has been influential to the field of software engineering and is regarded as an important source for object-oriented design theory and practice. More than 500,000 copies have been sold in English and in 13 other languages. Both the authors and the book are often referred to as the Gang of Four (GoF).
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Brown v. Board of Education in 1954.