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beroal

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in English [Jul. 1st, 2020|12:00 am]
beroal
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Welcome!

Posts in English in this blog: HTML; Atom.

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Short proofs in Coq.

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по-русски [Jun. 1st, 2020|12:00 am]
beroal
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Добро пожаловать!

Для обратной связи пишите сюда комментарии. Если я не добавляю вас в друзья, это не значит, что я вас не читаю.

Поисковые системы на платформе Google Custom Search Engine:
против мошенничества

only Haskell (the programming language)

OpenSearch plugin (то есть для Firefox) для поиска по:

Математические доказательства на языке Coq. Всякая мелочь, среди крупных модулей можно выделить CategoryTheory, IntBipart (целые числа как кольцо Гротендика), TakeDrop («take» и «drop» из Haskell.Data.List).

Лента выбранных мною из чужих блогов записей:


У меня есть личный веб-сайт.
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телефонный спам [Sep. 3rd, 2018|07:46 pm]
beroal
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Всё, что не модерируется, скоро зарастёт спамом. Включая телефонную связь. Как вы думаете, для телефонов сделают спам-фильтры, или люди просто перестанут пользоваться телефонами?
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information search [Sep. 3rd, 2018|06:42 am]
beroal
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A little prediction. People will move information search from Google to social networks so they can filter search results according to their preferences. Google will be useful only for search queries that return a small number of results due to its big database. Consequently, Google will concentrate on information preservation and abandon complex rating algorithms.
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Java precisely [Jul. 22nd, 2018|03:45 pm]
beroal
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Вышло новое издание книги «Java precisely» by Sestoft. Теперь я могу быть свободен от невнятных объяснений на пальцах. ☺ Предыдущий пост.
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пожертвуй бизнесмену [Jul. 17th, 2018|07:20 am]
beroal
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Люди предлагают бесплатную услугу в интернете и просят пожертвовать на неё. Видимо, сейчас совсем плохо учат экономическую теорию. Не знают, что за услугу можно просто требовать деньги. ☺
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safe programming language [Jul. 3rd, 2018|09:02 am]
beroal
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Safe programming languages are gaining popularity. I wonder what is the formal definition of safe PL. For example, C is not safe, but Java is safe. I suspect that the property “safe” should be applied to a PL implementation rather than to the PL itself. If so, let’s discuss a definition of safe PL implementation. My own attempts to formalize this notion led to a strange outcome, so I would like to hear other opinions. Please, do not say that every PL has unsafe commands. We can always take a safe subset.

My definition of safe PL implementation refers to the notion of multithreading which I will not define here. Informally, a PL implementation is safe if it does not spoil the execution of other threads. A PL implementation impl is safe iff for any two threads thread_0 and thread_1 such that thread_0 runs impl, the real semantics of thread_1 is equal to its official semantics. By the official semantics of thread_1, I mean the semantics of the program that thread_1 runs according to the semantics of the PL in which that program is written. By the real semantics, I mean the behavior of thread_1 as it runs along thread_0. The real semantics may differ from the official semantics because of thread_0 interfering with thread_1, for example, writing to the memory region belonging to thread_1. As usual, semantics does not include running time or memory consumption.
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letters and symbols instead of words [Jun. 20th, 2018|09:08 pm]
beroal
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Discussion.

With time, I came to appreciate mathematical convention of writing letters and symbols instead of words. First, it is easier to comprehend a formula if it is compact, fits into a view. When learning mathematics, at least abstract mathematics, understanding is much harder than remembering meanings of letters. I spend more time pondering than remembering. IMHO, letters are actually more efficient than words, and names composed from several words will make mathematics unreadable. BTW, mathematicians use words, but abbreviated (for example, “lim”, “ker”, “dim”). Compactness is the key.

Second, as was pointed out, it is really hard to invent names for abstract entities. Our words come from everyday life which does not contain abstractions. At the end, “x_0”, “x_1”, “y_0”, “y_1” seem like really good names, especially if you write the same index for corresponding values. The real issue is that entities are abstract, not names. Example. When stating associativity, what variable names are better than (x_0 x_1 x_2), (x y z), or (x x' x'')? What “meaningful” names would you propose?

This does not mean that I do not see defects in mathematical notation. The drive for compactness led us to notation where some things are omitted and a symbol mean different things. “×” is omitted even in schools. Parentheses are used for grouping terms in expressions, tuples, GCD, permutations… Sometimes it really hinders understanding.
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Social aspects of MLRISC [May. 21st, 2018|10:38 pm]
beroal
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Social factors determine programming landscape no less than technical ones. Ideas, “technologies,” or programs enjoy different popularity even if they have equal technical merits. I think this may be a fruitful field of study for social scientists. PHP is a good example. How has the shitty programming language PHP become so popular? There are many technically better programming languages (PLs). So this phenomenon has to be explained by social factors. (And I actually think that the obscene word is a correct scientific term in this context.)

to be continuedCollapse )
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investigation of the meanings of programming terms [May. 17th, 2018|08:07 pm]
beroal
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Any discussion on the foundations of computing runs into severe problems right at the start. The difficulty is that although we all use words such as ‘name’, ‘value’, ‘program’, ‘expression’ or ‘command’ which we think we understand, it often turns out on closer investigation that in point of fact we all mean different things by these words, so that communication is at best precarious. These misunderstandings arise in at least two ways. The first is straightforwardly incorrect or muddled thinking. An investigation of the meanings of these basic terms is undoubtedly an exercise in mathematical logic and neither to the taste nor within the field of competence of many people who work on programming languages. As a result the practice and development of programming languages has outrun our ability to fit them into a secure mathematical framework so that they have to be described in ad hoc ways. Because these start from various points they often use conflicting and sometimes also inconsistent interpretations of the same basic terms.

Christopher Strachey. “Fundamental Concepts in Programming Languages.” (Written in 1967.)
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