computer science

Kosaburo Hashiguchi

Kosaburo Hashiguchi is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Kosaburo Hashiguchi rather than just read about it. In short: Kosaburo Hashiguchi (橋口攻三郎, Hashiguchi Kōsaburō) is a Japanese mathematician and computer scientist at the Toyohashi University of Technology and Okayama University, known for his research in formal language theory. In 1988, he found the first algorithm to determine the star height of a regular language, a problem that had been open since 1963 when Lawrence Eggan solved the related star height problem, showing that…

Key takeaways

Kosaburo Hashiguchi belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Kosaburo Hashiguchi to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Kosaburo Hashiguchi from memory before moving on to harder problems.

Reference excerpt

Kosaburo Hashiguchi (橋口攻三郎, Hashiguchi Kōsaburō) is a Japanese mathematician and computer scientist at the Toyohashi University of Technology and Okayama University, known for his research in formal language theory. In 1988, he found the first algorithm to determine the star height of a regular language, a problem that had been open since 1963 when Lawrence Eggan solved the related star height problem, showing that there is no finite bound on the star height. Hashiguchi's algorithm for star height is extremely complex, and impractical on all but the smallest examples.[H88] A simpler method, showing also that the problem is PSPACE-complete, was provided in 2005 by Kirsten. Earlier, in 1979, Hashiguchi had also solved another open problem on regular languages, of deciding whether, for a given language A {\displaystyle A} , there exists a finite number n {\displaystyle n} such that A n = A ∗ {\displaystyle A^{n}=A^{*}} .[H79] Hashiguchi is the uncle of Japanese-born American pianist Grace Nikae.

Selected publications

References

External links Home page

Worked examples

Example 1 — a first encounter with Kosaburo Hashiguchi

Start with the simplest possible case. Write down what Kosaburo Hashiguchi claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Kosaburo Hashiguchi before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Kosaburo Hashiguchi ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Kosaburo Hashiguchi

In research: Kosaburo Hashiguchi appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Kosaburo Hashiguchi in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Kosaburo Hashiguchi is common in secondary-school and first-year university syllabi. It links to neighbouring topics Japanese computer scientists, Japanese mathematicians, Living people, so understanding it makes those chapters shorter.
In everyday life: Look for Kosaburo Hashiguchi outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Kosaburo Hashiguchi in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Kosaburo Hashiguchi means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Kosaburo Hashiguchi out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Kosaburo Hashiguchi in simple terms?

Why does Kosaburo Hashiguchi matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Kosaburo Hashiguchi?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Kosaburo Hashiguchi.