## 2008-12-15

### A machine which executes a procedure ... Pop1 (1)

Japanese version

It has been while. We thought about a machine which generates the next number of the input last time. Here, we have seen a procedure of ''increment one.'' We coined this procedure as ''increment one,'' like there is something meaning. Or for human, this procedure has a meaning, ''increment one.'' But, the machine SUCC 1 just moves some symbols around. I think SUCC 1 did not understand the numbers. Here is too much to think about what is ''meaning'' or what is ''understanding.'' There is a hypothesis called ''Society of Mind'' by Marvin Minsky (this is a nice book and I recommend this.) which said a complex combination of simple functionalities creates intelligence, or you can not distinguish such complex thing from an intelligent thing. But SUCC 1 is such a simple machine and I believe I could safely say it has no intelligence. (By the way, are there any relationship between Marvin Minsky and the robot Marvin?) Although human being prefers that a machine performs something meaningful, it does not matter for the machine (or a machine can not matter anything so far). Performing a procedure becomes a computation. It is not necessary to understand what the computation means to perform computations.

SciFi novel usually describes this as a problem. A machine just executes its instructions without any understanding. We can make any dangerous machine (from Cordwainer Smith, The Instrumentality of Mankind's Menschenjager to a movie Terminator, and so on) Only moral can stop this. My favorite is ''Variant 2'' by Philip K. Dick, but it is too much here, so back to lambda calculus.

Figure 1 shows the machine POP1. POP1 can execute three instructions.

Figure 1: Pop1

(a) Copy input to output: Copy the contents of input table to the output table. (Figure (a))
(b) Remove head and tail: Remove head and tail on the output table (Figure (b))

These instructions are always valid if the input is a Church number. If the input is not a Church number, POP1 casts an error, usually it gets angry and throws the numbers to you. Sirius Cybernetics Coop.'s manual states that ''Please put a helmet on your head before running the program of POP1.''

Next time, let's write a POP1's program using these POP1 instructions.

## 2008-12-10

### Three guests in a restaurant... meaning of computation (1)

Japanese version

Several weeks ago, one of my friends visited me. We told about lambda calculus and the meaning of computation. Lambda calculus tried to define the computation only in a formal way without thinking its meaning. On the other hand, it is usually important what I am computing in every day life. Interestingly, I started to think about the meaning of computation more deeply when I think about how-to-not-to-think-about-the-meaning. I think something I start to understand when it was missing.

There is a film called ``Paper moon''. In the film, there are several cheating methods which are good examples of using misunderstanding of meaning of the computation. If I remember correctly, a classic Japanese Rakugo, ``Tubozan'' has the same tricks. There is also a good example of how a physicist connects the meaning and computation in a book, ``Surely You're Joking, Mr. Feynman!.'' In this article, ''three guests in a restaurant''is a famous story, but even my friend still needed some time to understand what the problem is

There are three guests in a restaurant. They took a course menu and it costs 300 Euro. A waiter collected money from the guests and backed to the kitchen, then the master said, ''Today is the anniversary day of the restaurant, so the course costs 250 only.'' The waiter came back to the table, but, he thought, ''50 Euro is hard to divide by three persons.'' Then, he said ''Today is our restaurant's anniversary day, so 30 Euro back. Each can get 10 Euro.'' The guests thanked the waiter and left the restaurant. The waiter felt a bit guilty, but, he decided to forget it. However, he realized a bit odd. ''Each paid 90 Euro, so the sum was 270, I have got 20 Euro from them. But the sum is 270 + 20 = 290 instead of 300Euro. Where is the 10 Euro?''

I actually thought this works only in Japanese. But, that worked in German. Later I tried another friend with in English, it seemed working. You might figure out what is wrong here. Even so, it is hard to make a good explanation. If you did not know this story, please think though it.

## 2008-11-26

### Laplacian matrix and its eigenvalues

Japanese version

Today, I read a paper, ``A signal processing approach to fair surface design'' (G. Taubin), but I did not understand it. It said that the eigenvalues of a Laplacian matrix like Equation 1 is Equation 2.
Eq 1Eq 2

Today, my friend CR taught me why this is. Actually, it is not so difficult. Here, we can back to the basics of eigenvalues, a characteristics function:
Also we know a Laplacian matrix is a second order differentiation. Therefore, it is
One of the solution of this differential equation is exponential function (since the second derivative is back to the original one except a constant factor). If you remember the Euler's equation, you can get Equation 2.

Additionally, Equation 1 is symmetric. Therefore, its eigenvalues are real and eigenvectors are orthogonal. Moreover, this is a diffusion equation and you can see the relationship with Fourier
basis.

Now, I can see why the paper's title is ``signal processing approach.'' But, one who is not familiar with mathematics like me, it is hard to understand the logic as ``The Equation 1's eigenvalues can be written as Equation 2. Therefore, we could decompose the signal...''

Of course, this is easy for the professionals and it is too verbose to write this like this article. However, at least I need this kind of explanations. Thanks CR.

## 2008-11-21

### Foldable Computer

Japanese version

If I remember correctly, when I was a high school student, there was a exhibition near a station. The theme was Children's dream and it was provided by a Kindergarten. Each child draws a picture with a title "I wish it was ..." Some already drew a picture to please their parents. Some others were totally free from anything. One of my friend G is a designer and once told me that "A picture by a child is very strong and I sometimes feel I can never overcome their drawing." He also said, "They never consider an object must have some three dimensional constraint. They draw as they feel when they saw a thing, which is totally irrelevant what they saw. Their drawings have overwhelming power." When a child feel "The mouth is big!", then she/he draws a mouth that is larger than the face without any doubt. He even feels some kind of fear in their picture with incredible freedom.

I remember one of them, "Flexible sized television." A boy wanted to have a television, which expands when he pulled it. All his family pulled their television to make it larger in the picture.

For more than 10 years, quite a few times I was disappointed to see a new television. It is just larger and still I can not change the screen size. Still we can not make a resizable TV, a notebook, or iPod. I may buy one if it is resizable.

I remember I told about this story with a friend he passed away last week. We told a lot of things including this TV. I told him other rather boring stories, like "Current computer graphics is not good at to make the scene dirty. A city has no garbage, all the pitching street has no defect, all the windows are perfectly clean, and all the cars are new." I remember he told me "Indeed, the real world is filled by dirtiness. This poster has a fold." when we walked along a super market just has opened. He always listened my such boring stories.

One day, the resizable TV would be invented. Today, I heard about the foldable display. Oh my friend, I miss you that we could not talk with how the world is changing. I never knew we spend such a precious time.

UIST 2008 (http://www.acm.org/uist/uist2008/)

## 2008-11-13

### friend

Yesterday I lost a friend.

I don't know why.

I feel something wrong in this world, but I wish he never left.

I liked him.

The world became a bit less attractive.

All my wish was just him alive.

Disappointed.

I miss him.

May rest in peace.

Sorry for our loss.

## 2008-11-06

### Edinburgh

Japanese version

Last week, I visited to my old friends in Edinburgh and Durham. Walking in the old city with my friends, that was fun holidays.

The history of the train system started in the United Kingdom. Therefore, I thought the train system is also advanced, however, it seems not so. For example, you can see the hand-written cargo numbers. Our train was missing one coach J, and the announce was "Today, we are missing one coach J. If you have a reservation in the coach J, you can find your seat in coach B. If you have a reservation in the coach B and can not find your seat, you can find it in coach F. Sorry for the inconvenience." We thought, wow, in England, the system is so difficult. How the people can manager that? But soon we found out many people were walking around and asked "Do you know where the coach x's seat?" We told a woman about the announce and she said, "What a beautiful organization!" I see why the English comedy is so good.

## 2008-10-22

### A machine which execute a procedure: SUCC mark I

Japanese version

Blaise Pascal made a calculator for helping his father's job (tax calculation). Usually it is painful to calculate a huge amount of accounting. I am not good at calculation. So, I thought if I have a computer, I do not need to compute anything myself. That's one of the motivation I took a computer science course in my University. Some people totally misunderstand that a computer scientist is good at arithmetic. No. If someone is good at arithmetic, why does she/he need to learn that? If a human can fly faster than sound, maybe we do not need to use a plane. If people can communicate without speaking between thousand kilometers away, why we need a telephone? I can not do arithmetic, therefore I learned computer science. So, let's make a computer.

Figure 4 is a computer SUCC mark 1 by Sirius Cybernetics corp. This computer gets one Church number as an input, and outputs another Church number. This computer does not understand what the number is, but just execute one procedure (it will be shown up soon). It is a kind of vending machine. As a vending machine can calculate changes, this SUCC mark I also can compute something.

SUCC mark I runs computation as the following.

1. Figure 5. Initial state. Given an input Church number on the 'input' board. Here, Church number 0 (Zero) is the input as an example. (Do you remember that the Church number 0 is one circle and one square?)

2. Figure 6. The input is copied on the output. SUCC mark I scan the input and choose the same tile from left to right.

3. Figure 7. The calculation result. After the copy, SUCC mark 1 puts one more square tile at the end of the output.

As you see, when we input the Church number 0, then the machine outputs Church number 1. The same procedure can generate 2 from 1, 3 from 2, and so forth. Finally, we have a computer! and please shut up, Marvin.

Marvin: ....

It seems ridiculously simple, but this is the basic of our computer. By the way, SUCC represents Successor. This is a successor number generator. As we have already seen, this function and Zero generates all natural numbers. We could add more procedures. Next time we will see a little bit more complex computation.

## 2008-10-18

### Church numerals continued

Japanese version

Last time, a circle was a symbol to represent a number. But, there is no such thing (a symbol to represent a number) in the Peano's axiom. Peano's axiom only define a Zero and a successor. we employed a square to represent Zero. But when we tell two numbers to a machine, we can not distinguish two numbers if we have only Zeros. See Figure 2. Therefore, we use a circle as a delimiter. One could say, we can use a space, but we also need to tell a space to a machine, otherwise any machine can not know a space exist. We need something like a number 0. 0 means ``there is nothing.'' If we write down nothing, how we could know something is missing. If we put 0, then we know nothing actively exists. 0 can represent ``existence of nothing.'' This is an excellent invention of human being.

By the way, speaking about space, there is no space character in Japanese. I think also Korean and Chinese do not have space character. Therefore, a processing of Asian text starts with finding words. A space character represents no character, but existence of no character makes so easy to find words. Space character is also a brilliant invention. I remind myself that Lao-tsu's ``usefulness of
uselessness.''

The Church numerals, one of the representations of numbers of lambda calculus, are defined as follows:

0 := λ f x. x
1 := λ f x. f x
2 := λ f x. f (f x)
3 := λ f x. f (f (f x))

It seems these are not numbers, but these satisfies Peno's axiom, therefore, these are numbers. Because no matter what it looks like, Peano's axiom defines what the number should be. If the condition is satisfied, they are numbers. That's the rule. If you closely look this numbers, the number of 'f' is represents the number. Zero has no `f,' 1 has one `f'. Two has two `f's . Three are also the same. This is the definition of Church numerals. As you see in Figure 3, this is almost the same as Figure 1's number. (Almost means both f and x are square. Different things should have different symbols. This is not good, but this is for computation.)

Marvin: What a long story to define just NUMBERS! You spent nine articles to define it. In the Wikipedia's lambda calculus page, when the Church numerals are defined, it has already defined all formal lambda expressions. You said just one is one square, two is two squares, ... this simple thing took so long. It is ok to explain something simple, but it is so pedantic. You have not even defined how to compute numbers. I have experienced five universes time. But this is too slow for me. So depressed.

But Marvin, this is the way I understand the Church number. I am a armature mathematician, so I could not understand if only the definitions of Peano's axiom is presented. It is so abstracted and dry for me.

Marvin: Doesn't matter. I am tired. You defined numbers. Now what? Roman number is better than this for computing. How can you write 2008? My co-processor will be depressed.

OK. We have now numbers, let's compute it... so functions.

## 2008-10-15

### DDR Gebaeude

Last Saturday, I walked around the city with my friend. DDR buildings are a bit chilly... Or it is already winter here.

## 2008-10-14

### Church numerals

Japanese version

Last time we were talking about how Peano defined the natural number. Because Lambda calculus defines the numbers based on that. Mathematical formulation makes the discussion (proof) more exact, this ``exact'' is important for mathematician. But, the formulation causes increasing the exactness, which means, there are no such thing, like ``You know about the numbers, just do something like calculation in appropriate way.'' Because even every single obvious issue should be defined in formulation. As the side effect, we could execute these rules on a machine --- we can make a computer! That's the interesting point for me.

There are many ways to how to implement a computer as a machine. Pascaline and Charles Babbage's differential engine are gear based. Here our base is Peano's axiom.

Before Marvin points out, this explanation is Masahiko Sato and Takafumi Sakurai's ``Basic theory of programming.'' (By the way, It is not so convenient that I left all my books in Japan. In Japanese version of my blog is written by SKK input method, which was first implemented by Masahiko Sato.) Prof. Sato's class was tough. At least I had totally no idea if I only attended. However, when I asked questions, even though it is extremely stupid questions, he answered the question until I said ``thanks I understand.'' The problem is the class was so tough, therefore I do not have any questions, except ``What can I ask?'' It is very difficult to figure out what is I don't figure out.

Here, I use a circle as a sign of ``This is a number.'' I use a square as Peano's ``zero,'' and a successor number is represented by reputation of ``zero''. See Figure 1.

As you see, there is no one or two. We have only a sign of ``number'' and ``zero.'' Our number system is depends on base 10 system. We could also use Roman number system, Babylonian system, or Chinese characters. These are all for human's convenience, and all of these number representations are not substance. Zero is sufficient to represent the Peano's system. I use zero as a square, since I would like to stress that ``zero'' is also a name for something. It does not matter if it is ``hoge,'' or "Petrosiliuszwackelmann." Then I use a square as following the Prof. Sato's book.

When you see one square, then I understand you want to call it one. I agree with that. But, we need to represent Zero. The usual number 0 means ``There is nothing here'' -- nothing exists here. If we want to start the number zero, then I think this is the way. Although, Peano's system can start any number of natural number, one, two, or 42. It does not matter. But still I would agree with Figure 1's zero looks like one.

## 2008-10-13

### Defining natural numbers 2

Japanese version

This is continued from the last article. Please refer the Peano's axiom in the last article.

The second definition means that we can create a next natural number from the current one. This function creates a successor number from the current number, therefore it called ``successor'' function. This defines ``plus one'' function. We have already the first natural number, zero, then we can make a successor number from zero. This successor number is ``something'' of zero. It is usually called one, but not necessary. This definition just said, it is something different from zero. We have now:

1. there is the first number,
2. we can make a successor number from a number.

Out of these two definitions/rules, it seems we can make the whole natural numbers, but this is not enough for that.

The third definition said that there is no loop of successor function, i.e., if you repeat the successor function staring with x, the result of them will never return to the number x. This seems natural since x + 1 + 1 ... + 1 != x. There is such mathematics (modulo), however, Peano's natural number does not think about that. For example, there are such system, like 12 + 1 = 1, or 31 + 1 = 1. If you think this is odd, think about your calender. Amazingly, the next day of December 31st (31.12) is January 1st (1.1). If you look at the month part, 12 + 1 = 1 and days part is 31 + 1 = 1. Time has also similar system, next of 23:59 is 00:00, means 59 + 1 = 0. Some might say that is not a calculation, but, there is such calculation in your computer. Someone may think 1 + 1 = 2 is the simplest mathematics. I think it is not so simple.

The fourth definition said that the same number's successors are always the same. In other word, different two numbers's successors are never the same. The calender example also does not follow this rule. 31 + 1 = 1 for January, 28 + 1 = 1 for February, 30 + 1 = 1 for April. 31, 28, 30 are not the same number, but the + 1's result are all 1. This definition tells you that the calender system never happens in the natural number.

I think now Marvin want to complain my explanation since these are so obvious and not need to explain. The last definition said all the natural numbers follows this rule are also the natural number. (This is the base of mathematical induction.)

Marvin: ``By the way, this explanation is quite similar to the explanation from Kouji Shiga's book. You should refer that.'' That's true. This explanation comes from ``A story of growing mathematics.'' Unfortunately, I do not have this book now. I left them Japan... I like all the Shiga's book. When I found out that he had a open seminar at Yokohama, I visited his class. But it took four hours to go and back the class by train. It was fantastic classes. When I left Japan, I regret that I could not take his class anymore.

Peano's axiom reminds me two things: Lao-tsu and Wittgenstein. The coincidence works again for the guide. The section 42 of Lao-tsu starts with ``Tao is created by one. One bears two, two bears three, and three bears everything...'' Excellent.

I have no idea about what Wittgenstein try to explain, however, his word: the words are just projection of the world. I think it sounds right. Lambda calculus projects back this words to a machine. I.e., logic (logos) is projected to the world again. So far, I just describe calculation with words. But no matter what words I use, this can be run on a machine, which belong to the world. I am satisfied when I see the logic really runs on a machine. Then I feel this is not just meaningless words.

Next time, let me describe the natural numbers by lambda.

### Blaues Wunder

Japanese version

A few weeks ago, I visited Dresden and saw a bridge called Blauses Wunder. The formal name of the bridge is Loschwitzer Bruecke, but even this name is on a map. The literal meaning of this word is ``Blue Wonder,'' but in German, there is another meaning -- very surprising in a bad way. This is bit strange... The originally this bridge was blue. Dresden is a beautiful city. I have friends there, so I visited there several times.

I first know the word, Blauses Wunder in the book from Preussler, ``Der Raueber Hotzenploz.'' (Am Ende der Spur sollte jeder von beiden sein blaues Wunder erleben, dafuer hatte Hotzenploz vorgesorgt. in Chapter 6)

Größere Kartenansicht

## 2008-10-08

### Defining natural numbers 1

Japanese version

Peano defined natural numbers.

He actually described properties of natural number, not seems to try to define the natural numbers. But these are somehow the same. The following five definitions are called Peano's axiom which defines the natural numbers. If you are not familiar with mathematical notation, it might be hard to get what they said. But, the basics are not so difficult. These are copied from Mathworld.
1. Zero is a number.
2. If a is a number, the successor of a is a number.
3. zero is not the successor of a number.
4. Two numbers of which the successors are equal are themselves equal.
5. (induction axiom.) If a set S of numbers contains zero and also the successor of every number in S, then every number is in S.
The first definition said, there is the first number called Zero. Here it said Zero, but it does not matter which number is. It should be a ``something.'' However, you may ask ``What is something?'' It is really just ``something.'' Why we need to say the first number as Zero? It is fine as One, 42, -1, or x... You can write in Japanese ``Rei'', or in German, ``Null.'' In short, this is ``something.'' But, one thing I would like to make this clear, this ``Zero'' is not the number 0. Because we want to define numbers, so we do not know any numbers, even 0. It is just something the first number and we can just call it Zero. Personally, I prefer to write x since it seems more ``something.''

Definitions are similar to rules of a game. Therefore, we should not think about why this is defined. That is just a starting point of the discussion. It is easy to imagine that this is hard for especially someone who is not familiar with mathematics. This is the same as rules of some game, like soccer game, ``A player is not allowed to touch a ball by hand except goalkeepers.'' If you ask ``Why a player can not use his/her hands?'' Then one can only answer that ``That's a rule of the soccer game.'' This is also true as the rule of chess, shougi, or go... If there are ten kind of games, there are ten kind of rules. Mathematics is the same, there are many rules of mathematics and each rule makes different mathematics. We can make arbitrary kind of mathematics, only necessary condition is such mathematical system must be consistent. But, most of the arbitrary rules can not make interesting mathematics. ``Interesting'' is quite subjective word and it seems not so fit to mathematics. But, many can feel that. I sometimes encountered that some people believe that the mathematics is a kind of truth in the universe. But, mathematics is nothing related with how the universe is. That's the physics' area. However, well established mathematics can describe our universe well. I am fascinated this interesting point of mathematics. It is like a game/sport that has a well established rule are so fun and interesting. As there are many kind of games and sports, there are many mathematics and each mathematics may have different rules. Although, many rules can be shared in mathematics. One can make up new rules and can create a new sports. But it is difficult to create a new interesting sports. It is the same in mathematics, you can create own mathematics easily by making up several definitions, but it is very difficult to make an interesting new mathematics.

By the way, one day for one small thema is still too long for blog for me, I will keep an article short from now on.

## 2008-10-06

One of my friends is an artist. Recently, he made an article, ``Stereo Shadow.'' He used two light sources, one is blue, the other is red. Audiences see their shadow with wearing a red-blue filter glasses. Then they can observe their own ``3D'' shadow in the wall. There were several exhibitions of this in Japan. I heard he has prepared a video of this, and I am looking forward to seeing that.

The black dots in the picture is for audience's safety. He found some children try to touch their shadow and hit the wall without noticing. So the dot shows ``Here, there is a wall'' sign.

## 2008-10-05

### Motivation of Lambda calculus

Japanese version

According to the Wikipedia's page, Lambda calculus was introduced by Church and Kleene in the 1930s as part of an investigation into the foundations of mathematics.

By the way, I am an amateur Sunday mathematician, therefore, please do not believe this blog without check by yourself. This is just I think I understand these stuffs. So I think there must be many errors. I try to avoid errors, but, this is not my profession. I am also not confident about my English. Welcome the comments.

The origin of this blog is Wikipedia. I could say in cool way, I was inspired by the Wikipedia's page. If you understand the Wikipedia's entry, I don't recommend to waste of time by reading this blog. There are bunch of interesting text around the world. When you read ``Lambda calculus was introduced by Church and Kleene in the 1930s as part of an investigation into the foundations of mathematics.'', and if you think ``I see, that's the reason of why lambda calculus was introduced. That's easy.'' then, you don't need to read this blog. But, if you think ``In 1930? It seems very recently as the history of mathematics. Why is the foundations of mathematics considered in this time? Wait, what is the foundations of mathematics? Didn't Pythagoras, Apollonius, or Euclid study the foundations of mathematics in B.C.?'' Then, you may continue to read this text.

The foundations of mathematics means that where the mathematics can start, or what kind of starting point is all right for mathematics system. Mathematics starts with a set of definition. A person should define them. One of the most fundamental mathematical object would be numbers. Also propositions and logic, how to calculate numbers would be fundamental stuffs in mathematics. These seems too obvious and many mathematicians did not care them until 20th century. Or Euclid did too good job about formulation and we needed not re-consider until 20th century.

But, why such obvious things are important at that time? Mathematicians started to think about formalization at that time. It may differ the mathematics between languages, how can we sure they are exactly the same. For example, number `1' is exactly the same in English and Japanese? Then, they wanted to define numbers. If someone want to define numbers, it should be done without using numbers. Otherwise, we can define the numbers as ``numbers are numbers.'' For example, ``Love is love,'' ``Consciousness is conscious of consciousness.'' These may be true, but, we can not use it to think about the foundations of mathematics. Then a question is how can we define numbers without using numbers. This seems paranoia, but, mathematicians are perfectionist.

I found this is an interesting idea. Because these are enough to formalized, abstracted, and simplified. We could make a machine to implement that system. If you want to create a machine to compute something, we need to make it by some kind of materials (water, stone, iron, ...). Zaphod may say with his two heads, ``You know, 1 or 2 or 3, something like that. Just make up a machine which can understand them.'' But I think this is not so easy. Numbers are such an abstracted idea. Abstracted means that there are a lot of applications. ``What is the common idea between the earth, humans, a bread, signals, Zaphod's heads, and a church?'' I can answer that ``they are countable.'' I've already said, but I have no idea how to teach the numbers to children. That's a highly abstracted idea.

The motivation of lambda calculus is to think about the foundations of mathematics. This means that re-thinking all the mathematical system from the numbers and calculus even though they seems so obvious by some kind of formulation. At that time, mathematicians are interested in more in the sanity of the mathematical system by formalization. However, this formalization is based on enough simple system and we could build a machine which can partially process the system. The reason I am interested in lambda calculus is this part ``we can build a machine of that.'' Also this is the reason that lambda calculus is the basic theory of the computer and computer languages.

Next time, let's define the natural numbers without using 1, 2, 3, ...

## 2008-10-04

### Introducing lambda.

Japanese version

Standard mathematics books explain mathematical stuffs as definition, theorem, proof, definition, theorem, proof, .... This is quite simple and enough abstracted. Therefore, we can also explain lambda calculus in the standard way. But Marvin will sure complain that is so depressed. More abstracted theory could be more applicable to many things. It becomes less unnecessary stuffs, then, it becomes simpler and also more beautiful in a sense. The theory is to the point when more abstract.

Japanese sword seeks for the beauty in the sword itself, it never decorates with some kind of jewels. Because a sword maker/master thinks the beauty comes from the sword itself. They shamed if they need to cover a sword with non-sword component. We can find many swords, staffs, ... are decorated with gold or some jewels. I can also see some kind of gorgeousness in that, however, I prefer beauty in these kind of simpleness. A French pilot said ``A designer knows he has achieved perfection not when there is nothing left to add, but when there is nothing left to take away.'' I sympathize with this word. Also, I like the story about a ship called Vasa, which sank in the sea. The story about a project manager (a Swedish King) requested too many features to his ship. Any software comes from Sirius Cybernetics coop. has too much features and hard to use, because the project managers believe that the customers want to have new features instead of a simple and stable software. (Kode Vicious Pride and Prejudice (The Vasa) CASM Vol.51, No.9)

The beauty of mathematics is in the simpleness and abstraction. I could understand that a mathematician wants to discuss more simple and more abstract entity. But then the mathematics becomes more difficult to the usual people like me. I see here some kind of closeness. If only a few people who knows mathematics well can enjoy the mathematics, that's a bit sad for me.

When I discover some beauty, I sometimes want to keep it to only myself. If I discover some beauty which nobody doesn't know, I feel some privilege. Because I need a lot of effort to find out something beauty in mathematics, it is a kind of reward for me. If I explain them to many people and people also find the beauty, that's nice. On the other hand, I sometimes feel some kind of loneliness. Like it is not only mine anymore. Someone who loves mathematics seeks for more beauty in that, then she/he may search for more abstract form. The result becomes more substance, all the background, history, etc. will be lost. That's also the reward for mathematicians. It is pure substance, however, it is not familiar with me anymore. I do not feel that I understand that anymore.

I also prefer abandoned extra part of mathematics. Why lambda calculus is created? How it is created? What was the first attempt of that? These may be not so important after constructed the lambda calculus. ``What can lambda do?'' becomes more important. Usually ``what is it?'' is not so important in mathematics like operators are more important than some kind of substances like numbers.

Vogons in the guide are extremely officious, their relationship is dry. Only important thing is what others can do for them. ``Who'' did is no matter at all. For them, even relative is only a relationship which people knows whom. Even if their grandmother ask to help her children, they do nothing unless there is a contract. A family may be worse than bureaucracy. A dry software company only asks employees to implement a new feature. This is important of course for business. But, who did it is not so important. This means, it does not matter who did that. It is just a function of the company. However, if a company does not applicate or does not matter the people, the people usually leave such kind of company. So, Vogonism is hardly work in the human society. But it seems Vogonism is working in mathematics theory.

The important thing of lambda is also what the lambda calculus can do. However, this is a Hitchhiker's guide. Let's talk about not-so-important things, like, why lambda is created. lambda calculus is also made by a person. Therefore, there must be some kind of motivation. Marvin is the most depressed existence in the universe, he (she/it?) has no motivation at all. He is always depressed, but he even has no motivation to suicide... But, the designer of Marvin from Sirius Cybernetics coop. did not want to make a depressed robot (I think). The designers just thought if they can combine a few hundreds of genius brains, such thing should be super-genus. However they are enough to smart to design Marvin, but they are not enough smart to imagine that such super-genius is usually insane. There is a purpose of lambda. Let's talk about the motivation of lambda next time.

## 2008-09-29

### Intermission 1 (lambda calculus)

I have a Japanese version of this page. There was a good question on my last article. ``What happen if the vending machine (a function) is broken?''

First of all, we need to define what broken means. Some of you would say, ``Broken is broken, what else?'' But, this answer does not make any sense for mathematicians. Are there no common sense in the head of mathematician? Maybe, yes. But, there is a reason.

I am a Sunday mathematician/programmer. Mainly I program a code to solve some of my problems. To tell my computer to solve my problem, I need to interpret my problem to a code which my computer can execute/understand. Many of mathematics formulation is really formulated, which means you do not need to understand what it is, they are just a procedure. Then my computer can execute to solve my problem. I formulate some problem since after that is done, I do not need to think about that. Rest of the problem is solved automatically. This is fun for me. ``Computer, search some information. Computer, find the shortest path from my home to the station. Computer, find the cheapest ticket under this condition...'' All these things must be translated to a code which my computer can understand. ``Broken is broken'' is not enough for the computer. Since computers are so stupid so far.

For example, Broken could mean 1. when you input something, but nothing comes out, 2. when you input anything, the output is always the same, or 3. when you input something, the output seems totally random. Which is the broken means for you? None of them? Current usual computer can not guess, we need to tell that.

Also, ``broken'' has subjective meaning. There are chips which have build-in self destruction mechanism. For example, some kind of decryption chips. These chips contain a secret encryption key, so some malicious people want to read it. When the chip detects such activity, it breaks itself. Some of the credit card chips and DVD copy detection chips have this function.

When you can not read the information, usually it means ``broken.'' But the designer of these chips designed to do that. If someone can still read the secret information, it is broken for the designer. Therefore, ``broken'' is subjective meaning. When someone's credit card is stolen, the owner usually does not want to his/her card available anymore. If the chip does not self destructed by the malicious one's attack, then the owner may sue the designer, ``The chip was not broken, because it was broken. If it is not broken, it should have broken itself.'' A human can understand this means, but, it is difficult for current machines.

Lambda calculus thinks about all kind of functions. Therefore, such ``broken'' function (whatever it means) must be described. If lambda calculus can not describe some of the functions, that is the limit of this calculus. But, a person must define what is the broken means if he/she want to describe it in lambda calculus. Mathematician is a such a lazy people, but they are also perfectionist. The art of mathematics is how to reach the ``perfect laziness.'' Therfore, all kinds of functions are of course considered. In the a few thousand years of mathematics history, one era is ended when the people found out the perfectness of mathematics system or limit of mathematics system. But this story is too large here and I would like to concentrate only at the some aspect of the lambda calculus. Although, I would like to mention about that if I could.

### realtime raytracing als 4k demo

Japanese version

My colleague told me this realtime raytracing demo with photon mapping (caustics). My machine has not enough power to run the demo. But it is quite impressive that just 4k bytes demo program can do this in realtime. Unfortunately, the code is not published.

The rendering time in a movie sometimes took 8 hours to render a frame. Which means it takes more than 8 days for one second movie. But these people usually has a render farm that contains 1000 or more computers. So, after they start render images, 1000 frames will be ready. For this demo we can take video directory. When you visit to YouTube, there are higher quality movie.

http://www.pouet.net/prod.php?which=51443

## 2008-09-23

### lambda calculus and function

(Japanese version )

The word lambda calculus itself has ``calculus,'' so it can also calculate numbers. But, when I started to learn the lambda calculus, I want to know that what is ``calculate'' means. Then I also think about ``what is the number?'' If I want to teach ``what is the number'' to small children, I do not know how to teach it. Also I did not recall how to learn that. But, I think I know what numbers are.

I can tell that there are some properties about numbers. First, it does not matter how to read it. In the hitchhiker's guide, there was a planet called Earth. The people on the planet have a lot of languages. For example, English, German, Latin, Japanese, and so forth. Interestingly enough, every language seems to have a concept about numbers. There are many representations for numbers, for example, (1, 2, 3, ...), (one, two, three, ...), (ein, zwei, drei, ...), (ichi, ni, san, ...), and so on. But no matter how you read them, there should be a common concept underneath. In the guide, maybe (herring, sandwiches, herring sandwiches, ...) or something like that. I know the definition by negation (it does not matter how to read them) is not a good idea here, but this at least tells you one aspect of numbers. There is a concept ``numbers'' which is independent from how to read them. Then, what is the substance of numbers? You can not say, it is one, two, three, ... Inside the guide, there must be ``something,'' and they are presented in some representation according to readers. The representation is always chosen as the reader can understand. I called it ``native'' in one section before. This is the substance of guide, someone could call it as information. But, it does not matter which language is employed to store such information inside of the guide. We could investigate further the substance of the guide and also substance of numbers.

I think lambda calculus is a mathematics that talks about function. Function is a useful idea in mathematics. It's like a vending machine that if you put something in (for example, money), then something comes out (for example, a drink). Many of the cases, people imagine a box which converts from something to another thing. For instance, a converter box which tells you that one Altair dollar is how much Sirius yen. The guide must also have such a box inside.

The function is not necessary to be a box. However, I learn in such way at my school. Moreover, the character of ``function'' in my language means ``a number box.'' So, I usually write a box and put a name like f or g. I think this was a standard on earth. Anyway, both teachers and students did not think about this deeply. Especially, if the usual people know what is function, then computer scientists have a problem that they do not know what it is. Nowadays function is a popular idea, so, computer scientists needs to invent something fancy.

Most of the computer scientists use the words ``lambda calculus'' as to deceive the people. It is easy to find such people, if you ask them ``What's lambda calculus?'' then they will answer, ``fixed-point...,'' ``Combinator blah,'' ``computability...'' to deceive you.

Lambda calculus might be a deep idea and might be useful to think about function. Although I am just a Sunday wannabe mathematician, I could enjoy some superficial results. I could even finish this with ``Church-Rosser blah blah'' to deceive you. However, as you know I am now writing this article. Such a person usually wants to brag that ``I know it! I know it!'' So, I will continue this story at least until Marvin will show up. By the way, Marvin is THE genus robot in the Hitchhiker's guide. He/(or She/It?) has the most depressed mind with the best brain ever made in the universe by Sirius cybernetics corporation. This company first made a brain which has equal ability to a few hundreds bionic brains. But the result shows that a genus is crazy. So be Marvin.

Finally, this section is ended here since I could write about my favorite Marvin.

## 2008-09-18

### lambda calculus and Hitchhiker's guide (1)

lambda calculus and Hitchhiker's guide

One day, I hit on to want to know about lambda calculus, and looked up Wikipedia. There are nice entry about that, but I could not understand some examples of calculation. It took a week to figure out. Maybe this is trivial, but I would like to brag myself about that. There is a common saying, ``they brag most who can do least.''

I am not familiar with lambda calculus. If I encounter something not familiar, I usually lookup some kind of guide book. I went to some city, I usually have a book called ``Chikyu no aruki kata (How to walk on the earth (in Japanese)),'' or Hitchhiker's guide to the Galaxy. This article could be a tiny version of a Hitchhiker's guide to lambda calculus.

According to the Hitchhiker's guide to the Galaxy, the Hitchhiker's guide to the Galaxy is the most successful book in the universe. However, it seems no one knows the book is written in which language. If that is the most successful book, it seems all the people living in the universe can read. Or, also according to the guide, there is no population in the universe, maybe no one read the book. But then what does the most successful mean...

The guide could have an artificial intelligence, and all the people might read the guide using a babel fish. (In case you do not know the guide, the babel fish is a translation fish between any kind of species in universe using some kind of telepathy. But the translation quality is sometimes not so good. There is a translation engine on the web after this fish.)

But the main character of the guide, Arthur, can read the guide before he implanted a babel fish, cannot he? Then, the guide should have some kind of a translator. There could be a tiny possibility that there is a earth language (Queen's English) version of the guide, but I am sceptical of that. Because the company that sells guide tried to sell one version of guide to all the parallel universe including the past and the future.

Even there is a translator included, there must be a ``native'' or ``internal'' language of the guide. I can not imagine what kind of language is used for the guide, but some part related logic or mathematics could be understandable. I am pretty sure some entries about mathematics or logic in the guide. It is interesting for me that what kind of logical expression in the guide. It seems it is infinite improbable, but, it may be lambda calculus.