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282 lines
6.8 KiB
Markdown
282 lines
6.8 KiB
Markdown
---
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filename: learnNim-cn.nim
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contributors:
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- ["Jason J. Ayala P.", "http://JasonAyala.com"]
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- ["Dennis Felsing", "https://dennis.felsing.org"]
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translators:
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- ["lzw-723", "https://github.com/lzw-723"]
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---
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Nim(原名Nimrod)是一种静态类型的命令式编程语言，
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它能在不影响运行时效率的情况下为程序员提供强大的功能。
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Nim语言高效、有表现力、优雅。
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```nim
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# 单行注释以一个#开头
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#[
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这是多行注释
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在Nim语言中，多行注释可以嵌套，以#[开头，以]#结尾
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]#
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discard """
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这也可以作为多行注释使用。
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或者用于无法解析、损坏的代码
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"""
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var # 声明(和赋值)变量
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letter: char = 'n' # 带或不带类型批注
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lang = "N" & "im"
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nLength: int = len(lang)
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boat: float
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truth: bool = false
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let # 使用let*一次性*声明和绑定变量。
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legs = 400 # legs是不可改变的。
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arms = 2_000 # _会被忽略，对long类型非常有用。
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aboutPi = 3.15
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const # 常量在编译时计算。这确保了
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debug = true # 性能，在编译时表达式中很有用。
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compileBadCode = false
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when compileBadCode: # `when`是编译时的`if`
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legs = legs + 1 # 这个错误永远不会被编译。
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const input = readline(stdin) # const在编译时必须是已知的。
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discard 1 > 2 # 注意：如果表达式的结果未使用，
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# 编译器会发出警告。`discard`绕过了这一点。
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#
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# 数据结构
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#
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# 元组(Tuple)
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var
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child: tuple[name: string, age: int] # 元组有*字段名*
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today: tuple[sun: string, temp: float] # 和*顺序*
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child = (name: "Rudiger", age: 2) # 使用字面值()一次性赋值全部
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today.sun = "Overcast" # 也可以单独赋值
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today.temp = 70.1
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# 序列(Sequence)
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var
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drinks: seq[string]
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drinks = @["Water", "Juice", "Chocolate"] # @[V1,..,Vn] 是序列的字面值
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drinks.add("Milk")
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if "Milk" in drinks:
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echo "We have Milk and ", drinks.len - 1, " other drinks"
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let myDrink = drinks[2]
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#
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# 自定义类型
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#
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# 定义你自己的类型使得编译器为你工作。
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# 这使得静态类型变得强大和有用。
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type
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Name = string # 类型别名为你提供一个新类型，
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Age = int # 该类型可与旧类型互换，但更具描述性。
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Person = tuple[name: Name, age: Age] # 也可以定义数据结构。
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AnotherSyntax = tuple
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fieldOne: string
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secondField: int
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var
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john: Person = (name: "John B.", age: 17)
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newage: int = 18 # 在这里使用Age比int要好
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john.age = newage # 仍然有效，因为int和Age同义
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type
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Cash = distinct int # `distinct`使一个新类型与它的基本类型不兼容。
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Desc = distinct string
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var
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money: Cash = 100.Cash # `.Cash`把int转换成我们的类型
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description: Desc = "Interesting".Desc
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when compileBadCode:
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john.age = money # 错误！age是int类型、money是Cash类型
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john.name = description # 编译器说：“没门！”
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#
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# 更多类型和数据结构
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#
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# 枚举类型只能具有有限数量的值之一
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type
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Color = enum cRed, cBlue, cGreen
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Direction = enum # 可选格式
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dNorth
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dWest
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dEast
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dSouth
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var
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orient = dNorth # `orient`的类型是Direction，值是`dNorth`
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pixel = cGreen # `pixel`的类型是Color，值是`cGreen`
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discard dNorth > dEast # Enum通常是“序数”类型
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# 子范围指定有限的有效范围
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type
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DieFaces = range[1..20] # 只有从1到20的int才是有效值
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var
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my_roll: DieFaces = 13
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when compileBadCode:
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my_roll = 23 # 错误！
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# 数组(Array)
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type
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RollCounter = array[DieFaces, int] # 数组长度固定
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DirNames = array[Direction, string] # 以任意有序类型索引
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Truths = array[42..44, bool]
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var
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counter: RollCounter
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directions: DirNames
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possible: Truths
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possible = [false, false, false] # 数组字面以[V1,..,Vn]表示
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possible[42] = true
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directions[dNorth] = "Ahh. The Great White North!"
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directions[dWest] = "No, don't go there."
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my_roll = 13
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counter[my_roll] += 1
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counter[my_roll] += 1
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var anotherArray = ["Default index", "starts at", "0"]
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# 可用的数据结构包括表、集合、列表、队列、压缩前缀树。
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# http://nim-lang.org/docs/lib.html#collections-and-algorithms
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#
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# IO和控制流
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#
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# `case`, `readLine()`
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echo "Read any good books lately?"
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case readLine(stdin)
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of "no", "No":
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echo "Go to your local library."
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of "yes", "Yes":
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echo "Carry on, then."
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else:
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echo "That's great; I assume."
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# `while`, `if`, `continue`, `break`
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import strutils as str # http://nim-lang.org/docs/strutils.html
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echo "I'm thinking of a number between 41 and 43. Guess which!"
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let number: int = 42
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var
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raw_guess: string
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guess: int
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while guess != number:
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raw_guess = readLine(stdin)
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if raw_guess == "": continue # 跳出循环
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guess = str.parseInt(raw_guess)
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if guess == 1001:
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echo("AAAAAAGGG!")
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break
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elif guess > number:
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echo("Nope. Too high.")
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elif guess < number:
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echo(guess, " is too low")
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else:
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echo("Yeeeeeehaw!")
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#
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# 循环(Iteration)
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#
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for i, elem in ["Yes", "No", "Maybe so"]: # 也可以是`for elem in`
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echo(elem, " is at index: ", i)
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for k, v in items(@[(person: "You", power: 100), (person: "Me", power: 9000)]):
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echo v
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let myString = """
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an <example>
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`string` to
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play with
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""" # 多行字符串
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for line in splitLines(myString):
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echo(line)
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for i, c in myString: # 索引和字符。或使用'for j in'只有字符
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if i mod 2 == 0: continue # 紧凑的'if'形式
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elif c == 'X': break
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else: echo(c)
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#
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# 过程(Procedure)
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#
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type Answer = enum aYes, aNo
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proc ask(question: string): Answer =
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echo(question, " (y/n)")
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while true:
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case readLine(stdin)
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of "y", "Y", "yes", "Yes":
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return Answer.aYes # 枚举类型可以
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of "n", "N", "no", "No":
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return Answer.aNo
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else: echo("Please be clear: yes or no")
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proc addSugar(amount: int = 2) = # amount默认是2，不返回任何值
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assert(amount > 0 and amount < 9000, "Crazy Sugar")
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for a in 1..amount:
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echo(a, " sugar...")
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case ask("Would you like sugar in your tea?")
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of aYes:
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addSugar(3)
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of aNo:
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echo "Oh do take a little!"
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addSugar()
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# 这里不需要使用`else` 。只能是`yes`和`no`。
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#
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# 外部函数接口(FFI)
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#
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# 因为Nim可以编译为C，使用外部函数接口(FFI)很简单：
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proc strcmp(a, b: cstring): cint {.importc: "strcmp", nodecl.}
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let cmp = strcmp("C?", "Easy!")
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```
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除此以外，Nim通过元编程、性能和编译时特性将自己与其他同类分离开来。
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## 进阶阅读
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* [主页](http://nim-lang.org)
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* [下载](http://nim-lang.org/download.html)
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* [社区](http://nim-lang.org/community.html)
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* [常见问题](http://nim-lang.org/question.html)
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* [文档](http://nim-lang.org/documentation.html)
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* [参考手册](http://nim-lang.org/docs/manual.html)
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* [标准库](http://nim-lang.org/docs/lib.html)
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* [Rosetta Code](http://rosettacode.org/wiki/Category:Nim)
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