請問ｄ句點解？

This could be misleading.

When I first read this paragraph, I though constant and variable refer to something like:
when we have an equation, x + y = 3 say, x and y are variables and 3 is a constant. Later I checked out the source, the text is drawn from Tarski et al's book, that the authors have a broader meaning for the term constant and variable.

Speaking of their usage, variable and constant are opposite to each other. If something is a variable, it can't be a constant, vice versa.

Then, how do we classify numbers? We have real numbers, complex numbers, integers, positive numbers, negative numbers, odd numbers, even numbers, etc. We group numbers for the sake of convenience. These groups are not necessary exclusive to each other, for example real numbers are subset of complex numbers; zero and positive numbers and negative numbers together form real numbers.

Another example, assuming (which may not be a good assumption) male and female are the only two kinds of humans. Then,
classifying human into male and female is like classification of symbols;
classifying human according to their hobbies is like classification of numbers.
When we classify human according to their hobbies, we may have a group of people who enjoy reading, a group of people who enjoy watching movies, etc. A person can belong to two or more groups.

明白兩者有什麼分別了,多謝你詳細的解釋,但d句好像與上文內容唔連接0甘0既,
好怪,
若果將這句"因此將符號區分為常項與變項,並不表示在數方面也可區分為常數與變數"
(擇自剛到手的中譯版)或者
The classification of the symbols into constants and variables, therefore, does not mean that there are similar classifications of the numbers in which numbers are classified as variable number or constant number.
取代原文,成段通曬,但又好似同英文原句意思唔同0甘0既,

定係我誤解了correspond to與familiar 的意思?

其實作者沒有說清楚 familiar classifications 是什麼意思。

中譯版將 does not correspond to any of the familiar classifications of the numbers 譯作「並不表示在數方面也可區分為常數與變數」？看來不對。

我會將 The classification of the symbols into constants and variables, therefore, does not correspond to any of the familiar classifications of the numbers 譯作「因此，將符號分為常項與變項這種分類，並不相當於數字的任何一種慣用分類」。

區分 symbol 是為了將各種 symbols 分門別類，就像將詞區分為動詞、名詞、形容詞等等，各種詞的性質和作用是不一樣的。

oriole
2008-07-21 01:45:12 number總係某一個number，無一個number係真係variable既。有x、y之類既mathematical expressions多數唔係完整句子。你繼續睇後面就明。

http://leetm.mingpao.com/cfm/Forum3.cfm?CategoryID=5&TopicID...

<>

知吾知其實講緊幾時既數學書？

Alfred Tarski was born in 1901... and the text was written in 1941... So, by "less recent", was he referring to those published in the early 20th century?

Thanks Nick. Interesting.

I am not sure what Tarski really refers here, and anyway, I seldom read math book well beyond the early 20th century.. ha. The whole passage sounds to me a bit mystical.

I am also confused by terminologies like "variable numbers" as referred. It seems to me that nowadays mathematics mostly treats a variable as a mapping, from a certain domain of defintion to its range of values. Like say, the position variable x(t) is defined for all time t>0 and takes values in R^n. So statements like "a variable taking up a constant value" is perfectly acceptable; this differs from the highlighted sentence in that it is not treating "variable" and "constant" at the same level. Ha..nevertheless, a terminology like a "constant function" is also widely acceptable, although a "constant variable" may sound a bit odd, in this case we just say,"variable x is a constant"...ha.

要睇上文下理

Alfred Tarski 係唔係語言學家?

他是邏輯學家和數學家。