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* feat: translation 50% of Numbers

* feat: translation 100% of Numbers

* Update 1-js/05-data-types/02-number/article.md

Co-Authored-By: Jason Huang <[email protected]>
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lenchen1112 and kaddopur authored Oct 30, 2019
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6 changes: 3 additions & 3 deletions 1-js/05-data-types/02-number/1-sum-interface/solution.md
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```js run demo
let a = +prompt("The first number?", "");
let b = +prompt("The second number?", "");

alert( a + b );
```

Note the unary plus `+` before `prompt`. It immediately converts the value to a number.
注意在 `prompt` 之前的一元正號 `+`,它將值立刻轉換為數值。

否則,`a``b` 是個字串,所以它們的加總將會是字串連接,也就是:`"1" + "2" = "12"`

Otherwise, `a` and `b` would be string their sum would be their concatenation, that is: `"1" + "2" = "12"`.
7 changes: 4 additions & 3 deletions 1-js/05-data-types/02-number/1-sum-interface/task.md
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---

# Sum numbers from the visitor
# 加總由訪問者輸入的數值

Create a script that prompts the visitor to enter two numbers and then shows their sum.
建立一個腳本,提示(prompt)訪問者輸入兩個數值,然後顯示它們的總和。

[demo]

P.S. There is a gotcha with types.
註:類型會有個問題。

17 changes: 8 additions & 9 deletions 1-js/05-data-types/02-number/2-why-rounded-down/solution.md
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Internally the decimal fraction `6.35` is an endless binary. As always in such cases, it is stored with a precision loss.
在十進位分數 `6.35` 的內部是個無窮二進位,在這種情況下,它的存放會有著精度損失。

Let's see:
來看這:

```js run
alert( 6.35.toFixed(20) ); // 6.34999999999999964473
```

The precision loss can cause both increase and decrease of a number. In this particular case the number becomes a tiny bit less, that's why it rounded down.
精度損失可能會導致數值的增減,在這個特殊情況下,數值變得稍微小了點,這就是為什麼它被向下進位了。

And what's for `1.35`?
`1.35` 呢?

```js run
alert( 1.35.toFixed(20) ); // 1.35000000000000008882
```

Here the precision loss made the number a little bit greater, so it rounded up.
精度損失讓該數值稍微大了些,所以它被向上進位。

**How can we fix the problem with `6.35` if we want it to be rounded the right way?**
**若我們想要它正確的進位,該如何修正 `6.35` 的這個問題?**

We should bring it closer to an integer prior to rounding:
我們應該在進位前讓它更靠近整數:

```js run
alert( (6.35 * 10).toFixed(20) ); // 63.50000000000000000000
```

Note that `63.5` has no precision loss at all. That's because the decimal part `0.5` is actually `1/2`. Fractions divided by powers of `2` are exactly represented in the binary system, now we can round it:

注意這個 `63.5` 完全沒有精度損失,這是因為小數部分的 `0.5` 事實上為 `1/2`。被 `2` 的次方所除的除法可以在二進位系統中被完全表示出來,現在我們可以進位它了:

```js run
alert( Math.round(6.35 * 10) / 10); // 6.35 -> 63.5 -> 64(rounded) -> 6.4
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10 changes: 5 additions & 5 deletions 1-js/05-data-types/02-number/2-why-rounded-down/task.md
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---

# Why 6.35.toFixed(1) == 6.3?
# 為什麼 6.35.toFixed(1) == 6.3

According to the documentation `Math.round` and `toFixed` both round to the nearest number: `0..4` lead down while `5..9` lead up.
根據文件 `Math.round` `toFixed` 兩者皆進位到最近的數值:`0..4` 向下捨去,而 `5..9` 向上提升。

For instance:
舉個例:

```js run
alert( 1.35.toFixed(1) ); // 1.4
```

In the similar example below, why is `6.35` rounded to `6.3`, not `6.4`?
跟上面類似的例子中,為什麼 `6.35` 會進位為 `6.3` 而非 `6.4`

```js run
alert( 6.35.toFixed(1) ); // 6.3
```

How to round `6.35` the right way?
要如何正確地進位到 `6.35` 呢?

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Expand Up @@ -15,9 +15,9 @@ function readNumber() {
alert(`Read: ${readNumber()}`);
```

The solution is a little bit more intricate that it could be because we need to handle `null`/empty lines.
解法較為複雜些,因為我們需要處理 `null`/空行。

So we actually accept the input until it is a "regular number". Both `null` (cancel) and empty line also fit that condition, because in numeric form they are `0`.
因此我們實際上一直接收輸入的東西,直到它是個 "正常的數值" 為止。`null`(取消)和空行這兩者也都符合此條件,因為在數值格式中它們都是 `0`

After we stopped, we need to treat `null` and empty line specially (return `null`), because converting them to a number would return `0`.
在我們停下來之後,需要是對 `null` 和空行特別對待(return `null`),因為轉換它們為數值將會回傳 `0`

8 changes: 4 additions & 4 deletions 1-js/05-data-types/02-number/3-repeat-until-number/task.md
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---

# Repeat until the input is a number
# 重複動作直到輸入的是個數值為止

Create a function `readNumber` which prompts for a number until the visitor enters a valid numeric value.
建立一個函式 `readNumber` 以提示(prompt)輸入數值,直到訪問者真的輸入有效數值為止。

The resulting value must be returned as a number.
結果值必須以數值回傳。

The visitor can also stop the process by entering an empty line or pressing "CANCEL". In that case, the function should return `null`.
訪問者也可以透過輸入空行或按下 "CANCEL" 來停止程序。在這個情況下,函式應該要回傳 `null`

[demo]

11 changes: 6 additions & 5 deletions 1-js/05-data-types/02-number/4-endless-loop-error/solution.md
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That's because `i` would never equal `10`.
這是因為 `i` 永遠不會等於 `10`

Run it to see the *real* values of `i`:
執行這段來看看 `i` *真實* 的值:

```js run
let i = 0;
Expand All @@ -10,8 +10,9 @@ while (i < 11) {
}
```

None of them is exactly `10`.
它們之中沒有恰好為 `10` 的值。

Such things happen because of the precision losses when adding fractions like `0.2`.
這種事情發生於因為加上像是`0.2` 這樣的分數,而導致的精度損失。

結論:在使用十進位小數時,避免相等性確認。

Conclusion: evade equality checks when working with decimal fractions.
4 changes: 2 additions & 2 deletions 1-js/05-data-types/02-number/4-endless-loop-error/task.md
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---

# An occasional infinite loop
# 偶發的無窮迴圈

This loop is infinite. It never ends. Why?
這個迴圈是無窮的,它永不停止。為什麼?

```js
let i = 0;
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10 changes: 5 additions & 5 deletions 1-js/05-data-types/02-number/8-random-min-max/solution.md
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We need to "map" all values from the interval 0..1 into values from `min` to `max`.
我們需要 "對應" 0..1 區間內的所有值至 `min` `max` 之間的值上。

That can be done in two stages:
可在兩步驟內完成:

1. If we multiply a random number from 0..1 by `max-min`, then the interval of possible values increases `0..1` to `0..max-min`.
2. Now if we add `min`, the possible interval becomes from `min` to `max`.
1. 若我們對 `max-min` 乘上一個在 0..1 之間的隨機數,則可能值的區間會由 `0..1` 增加至 `0..max-min`
2. 現在若我們加上 `min`,則區間將變成 `min` `max`

The function:
該函式:

```js run
function random(min, max) {
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9 changes: 5 additions & 4 deletions 1-js/05-data-types/02-number/8-random-min-max/task.md
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---

# A random number from min to max
# min max 的隨機數

The built-in function `Math.random()` creates a random value from `0` to `1` (not including `1`).
內建函式 `Math.random()` 建立一個從 `0` `1` 的隨機值(不包括 `1`)。

Write the function `random(min, max)` to generate a random floating-point number from `min` to `max` (not including `max`).
寫個函式 `random(min, max)` `min` `max` 中產生隨機的浮點數(不包括 `max`)。

Examples of its work:
可行的範例:

```js
alert( random(1, 5) ); // 1.2345623452
alert( random(1, 5) ); // 3.7894332423
alert( random(1, 5) ); // 4.3435234525
```

27 changes: 14 additions & 13 deletions 1-js/05-data-types/02-number/9-random-int-min-max/solution.md
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# The simple but wrong solution
# 簡單但錯誤的解法

The simplest, but wrong solution would be to generate a value from `min` to `max` and round it:
最簡單卻錯誤的解法,是產生由 `min` `max` 的值,再進位它:

```js run
function randomInteger(min, max) {
Expand All @@ -11,28 +11,28 @@ function randomInteger(min, max) {
alert( randomInteger(1, 3) );
```

The function works, but it is incorrect. The probability to get edge values `min` and `max` is two times less than any other.
這個函式可以運行,但它不正確。得到邊緣值 `min` `max` 的機率比其它值還要少了兩倍。

If you run the example above many times, you would easily see that `2` appears the most often.
若你執行上述範例許多次,你將會很容易就看到 `2` 較常出現。

That happens because `Math.round()` gets random numbers from the interval `1..3` and rounds them as follows:
那是因為 `Math.round()` 由區間 `1..3` 之間得到隨機數,並像下面這樣進位:

```js no-beautify
values from 1 ... to 1.4999999999 become 1
values from 1.5 ... to 2.4999999999 become 2
values from 2.5 ... to 2.9999999999 become 3
```

Now we can clearly see that `1` gets twice less values than `2`. And the same with `3`.
現在我們可以清楚看到 `1` `2` 還少了兩倍,且同樣情況對 `3` 也是。

# The correct solution
# 正確的解法

There are many correct solutions to the task. One of them is to adjust interval borders. To ensure the same intervals, we can generate values from `0.5 to 3.5`, thus adding the required probabilities to the edges:
對此課題有許多正確的解法,其中一種是調整區間邊界。要保證同樣的區間,我們可以從 `0.5 3.5` 之間來生成值,故此可讓邊緣加上所需要的機率:

```js run
*!*
function randomInteger(min, max) {
// now rand is from (min-0.5) to (max+0.5)
// 現在 隨機值從(min-0.5)到(max+0.5
let rand = min - 0.5 + Math.random() * (max - min + 1);
return Math.round(rand);
}
Expand All @@ -41,12 +41,12 @@ function randomInteger(min, max) {
alert( randomInteger(1, 3) );
```

An alternative way could be to use `Math.floor` for a random number from `min` to `max+1`:
另一個替代的做法是對於 `min` `max+1` 之間的隨機數使用 `Math.floor`

```js run
*!*
function randomInteger(min, max) {
// here rand is from min to (max+1)
// 這邊的隨機值由 min 到(max+1
let rand = min + Math.random() * (max + 1 - min);
return Math.floor(rand);
}
Expand All @@ -55,12 +55,13 @@ function randomInteger(min, max) {
alert( randomInteger(1, 3) );
```

Now all intervals are mapped this way:
現在所有區間以這樣的方式被對應:

```js no-beautify
values from 1 ... to 1.9999999999 become 1
values from 2 ... to 2.9999999999 become 2
values from 3 ... to 3.9999999999 become 3
```

All intervals have the same length, making the final distribution uniform.
所有區間有著同樣的長度,使得最後結果是均勻分佈的。

12 changes: 6 additions & 6 deletions 1-js/05-data-types/02-number/9-random-int-min-max/task.md
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Expand Up @@ -2,19 +2,19 @@ importance: 2

---

# A random integer from min to max
# min max 的隨機整數

Create a function `randomInteger(min, max)` that generates a random *integer* number from `min` to `max` including both `min` and `max` as possible values.
建立一個函式 `randomInteger(min, max)` 來生成一個從 `min` `max` 的隨機 *整數*,包含 `min` `max` 兩者皆為可能的值。

Any number from the interval `min..max` must appear with the same probability.
任何在 `min..max` 區間的數值必須以相同的機率出現。


Examples of its work:
可行的範例:

```js
alert( randomInteger(1, 5) ); // 1
alert( randomInteger(1, 5) ); // 3
alert( randomInteger(1, 5) ); // 5
```

You can use the solution of the [previous task](info:task/random-min-max) as the base.
你可以使用 [前一個課題](info:task/random-min-max) 的解答作為基礎來思考。

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