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| -rw-r--r-- | README.markdown | 5 | ||||
| -rw-r--r-- | git.html.markdown | 5 | ||||
| -rw-r--r-- | haskell.html.markdown | 2 | ||||
| -rw-r--r-- | python.html.markdown | 2 | ||||
| -rw-r--r-- | r.html.markdown | 315 | ||||
| -rw-r--r-- | ruby.html.markdown | 60 | ||||
| -rw-r--r-- | scala.html.markdown | 6 | ||||
| -rw-r--r-- | zh-cn/dart-cn.html.markdown | 498 |
8 files changed, 790 insertions, 103 deletions
diff --git a/README.markdown b/README.markdown index 77e09abd..efc2fa07 100644 --- a/README.markdown +++ b/README.markdown @@ -16,8 +16,9 @@ properly! The most requested languages are: -* Scala -* Javascript +* Go +* ~~Scala~~ +* ~~Javascript~~ ... but there are many more requests to do "every language", so don't let that stop you. diff --git a/git.html.markdown b/git.html.markdown index 00f38d60..d8537300 100644 --- a/git.html.markdown +++ b/git.html.markdown @@ -310,7 +310,12 @@ Pulls from a repository and merges it with another branch. # Update your local repo, by merging in new changes # from the remote "origin" and "master" branch. # git pull <remote> <branch> +# git pull => implicitly defaults to => git pull origin master $ git pull origin master + +# Merge in changes from remote branch and rebase +# branch commits onto your local repo, like: "git pull <remote> <branch>, git rebase <branch>" +$ git pull origin master --rebase ``` ### push diff --git a/haskell.html.markdown b/haskell.html.markdown index be7d8669..9847ef2a 100644 --- a/haskell.html.markdown +++ b/haskell.html.markdown @@ -131,7 +131,7 @@ add 1 2 -- 3 -- with backticks: 1 `add` 2 -- 3 --- You can also define functions that have no characters! This lets +-- You can also define functions that have no letters! This lets -- you define your own operators! Here's an operator that does -- integer division (//) a b = a `div` b diff --git a/python.html.markdown b/python.html.markdown index a32db51a..f0b74d08 100644 --- a/python.html.markdown +++ b/python.html.markdown @@ -6,7 +6,7 @@ filename: learnpython.py --- Python was created by Guido Van Rossum in the early 90's. It is now one of the most popular -languages in existence. I fell in love with Python for its syntactic clarity. Its basically +languages in existence. I fell in love with Python for its syntactic clarity. It's basically executable pseudocode. Feedback would be highly appreciated! You can reach me at [@louiedinh](http://twitter.com/louiedinh) or louiedinh [at] [google's email service] diff --git a/r.html.markdown b/r.html.markdown index 0240e8fb..dd94072b 100644 --- a/r.html.markdown +++ b/r.html.markdown @@ -5,7 +5,7 @@ contributors: filename: learnr.r --- -R is a statistical computing language. It has lots of good built-in functions for uploading and cleaning data sets, running common statistical tests, and making graphs. You can also easily compile it within a LaTeX document. +R is a statistical computing language. It has lots of libraries for uploading and cleaning data sets, running statistical procedures, and making graphs. You can also run `R`commands within a LaTeX document. ```python @@ -14,63 +14,244 @@ R is a statistical computing language. It has lots of good built-in functions fo # You can't make a multi-line comment per se, # but you can stack multiple comments like so. -# Hit COMMAND-ENTER to execute a line +# in Windows, hit COMMAND-ENTER to execute a line + + +################################################################### +# Stuff you can do without understanding anything about programming +################################################################### + +data() # Browse pre-loaded data sets +data(rivers) # Lengths of Major North American Rivers +ls() # Notice that "rivers" appears in the workspace +head(rivers) # peek at the dataset +# 735 320 325 392 524 450 +length(rivers) # how many rivers were measured? +# 141 +summary(rivers) +# Min. 1st Qu. Median Mean 3rd Qu. Max. +# 135.0 310.0 425.0 591.2 680.0 3710.0 +stem(rivers) #stem-and-leaf plot (like a histogram) +# +# The decimal point is 2 digit(s) to the right of the | +# +# 0 | 4 +# 2 | 011223334555566667778888899900001111223333344455555666688888999 +# 4 | 111222333445566779001233344567 +# 6 | 000112233578012234468 +# 8 | 045790018 +# 10 | 04507 +# 12 | 1471 +# 14 | 56 +# 16 | 7 +# 18 | 9 +# 20 | +# 22 | 25 +# 24 | 3 +# 26 | +# 28 | +# 30 | +# 32 | +# 34 | +# 36 | 1 + + +stem(log(rivers)) #Notice that the data are neither normal nor log-normal! Take that, Bell Curve fundamentalists. + +# The decimal point is 1 digit(s) to the left of the | +# +# 48 | 1 +# 50 | +# 52 | 15578 +# 54 | 44571222466689 +# 56 | 023334677000124455789 +# 58 | 00122366666999933445777 +# 60 | 122445567800133459 +# 62 | 112666799035 +# 64 | 00011334581257889 +# 66 | 003683579 +# 68 | 0019156 +# 70 | 079357 +# 72 | 89 +# 74 | 84 +# 76 | 56 +# 78 | 4 +# 80 | +# 82 | 2 + + +hist(rivers, col="#333333", border="white", breaks=25) #play around with these parameters +hist(log(rivers), col="#333333", border="white", breaks=25) #you'll do more plotting later + +#Here's another neat data set that comes pre-loaded. R has tons of these. data() +data(discoveries) +plot(discoveries, col="#333333", lwd=3, xlab="Year", main="Number of important discoveries per year") +plot(discoveries, col="#333333", lwd=3, type = "h", xlab="Year", main="Number of important discoveries per year") + + +#rather than leaving the default ordering (by year) we could also sort to see what's typical +sort(discoveries) +# [1] 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 1 1 1 2 2 2 2 +# [26] 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 2 3 3 3 +# [51] 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 +# [76] 4 4 4 4 5 5 5 5 5 5 5 6 6 6 6 6 6 7 7 7 7 8 9 10 12 + +stem(discoveries, scale=2) +# +# The decimal point is at the | +# +# 0 | 000000000 +# 1 | 000000000000 +# 2 | 00000000000000000000000000 +# 3 | 00000000000000000000 +# 4 | 000000000000 +# 5 | 0000000 +# 6 | 000000 +# 7 | 0000 +# 8 | 0 +# 9 | 0 +# 10 | 0 +# 11 | +# 12 | 0 + +max(discoveries) +# 12 + +summary(discoveries) +# Min. 1st Qu. Median Mean 3rd Qu. Max. +# 0.0 2.0 3.0 3.1 4.0 12.0 + + + + +#Basic statistical operations don't require any programming knowledge either + +#roll a die a few times +round(runif(7, min=.5, max=6.5)) +# 1 4 6 1 4 6 4 + +#your numbers will differ from mine unless we set the same random.seed(31337) + + +#draw from a standard Gaussian 9 times +rnorm(9) +# [1] 0.07528471 1.03499859 1.34809556 -0.82356087 0.61638975 -1.88757271 +# [7] -0.59975593 0.57629164 1.08455362 + + + + + + + + ######################### -# The absolute basics +# Basic programming stuff ######################### # NUMBERS -# We've got doubles! Behold the "numeric" class -5 # => [1] 5 -class(5) # => [1] "numeric" -# We've also got integers! They look suspiciously similar, -# but indeed are different -5L # => [1] 5 -class(5L) # => [1] "integer" +# "numeric" means double-precision floating-point numbers +5 # 5 +class(5) # "numeric" +5e4 # 50000 #handy when dealing with large,small,or variable orders of magnitude +6.02e23 # Avogadro's number +1.6e-35 # Planck length + +# long-storage integers are written with L +5L # 5 +class(5L) # "integer" + # Try ?class for more information on the class() function -# In fact, you can look up the documentation on just about anything with ? +# In fact, you can look up the documentation on `xyz` with ?xyz +# or see the source for `xyz` by evaluating xyz + +# Arithmetic +10 + 66 # 76 +53.2 - 4 # 49.2 +2 * 2.0 # 4 +3L / 4 # 0.75 +3 %% 2 # 1 + +# Weird number types +class(NaN) # "numeric" +class(Inf) # "numeric" +class(-Inf) # "numeric" #used in for example integrate( dnorm(x), 3, Inf ) -- which obviates Z-score tables + +# but beware, NaN isn't the only weird type... +class(NA) # see below +class(NULL) # NULL + + +# SIMPLE LISTS +c(6, 8, 7, 5, 3, 0, 9) # 6 8 7 5 3 0 9 +c('alef', 'bet', 'gimmel', 'dalet', 'he') # "alef" "bet" "gimmel" "dalet" "he" +c('Z', 'o', 'r', 'o') == "Zoro" # FALSE FALSE FALSE FALSE + +#some more nice built-ins +5:15 # 5 6 7 8 9 10 11 12 13 14 15 + +seq(from=0, to=31337, by=1337) +# [1] 0 1337 2674 4011 5348 6685 8022 9359 10696 12033 13370 14707 +# [13] 16044 17381 18718 20055 21392 22729 24066 25403 26740 28077 29414 30751 + +letters +# [1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o" "p" "q" "r" "s" +# [20] "t" "u" "v" "w" "x" "y" "z" + +month.abb # "Jan" "Feb" "Mar" "Apr" "May" "Jun" "Jul" "Aug" "Sep" "Oct" "Nov" "Dec" + + +# Access the n'th element of a list with list.name[n] or sometimes list.name[[n]] +letters[18] # "r" +LETTERS[13] # "M" +month.name[9] # "September" +c(6, 8, 7, 5, 3, 0, 9)[3] # 7 -# All the normal operations! -10 + 66 # => [1] 76 -53.2 - 4 # => [1] 49.2 -2 * 2.0 # => [1] 4 -3L / 4 # => [1] 0.75 -3 %% 2 # => [1] 1 -# Finally, we've got not-a-numbers! They're numerics too -class(NaN) # => [1] "numeric" # CHARACTERS -# We've (sort of) got strings! Behold the "character" class -"plugh" # => [1] "plugh" -class("plugh") # "character" # There's no difference between strings and characters in R +"Horatio" # "Horatio" +class("Horatio") # "character" +substr("Fortuna multis dat nimis, nulli satis.", 9, 15) # "multis " +gsub('u', 'ø', "Fortuna multis dat nimis, nulli satis.") # "Fortøna møltis dat nimis, nølli satis." + + + # LOGICALS -# We've got booleans! Behold the "logical" class -class(TRUE) # => [1] "logical" -class(FALSE) # => [1] "logical" +# booleans +class(TRUE) # "logical" +class(FALSE) # "logical" # Behavior is normal -TRUE == TRUE # => [1] TRUE -TRUE == FALSE # => [1] FALSE -FALSE != FALSE # => [1] FALSE -FALSE != TRUE # => [1] TRUE +TRUE == TRUE # TRUE +TRUE == FALSE # FALSE +FALSE != FALSE # FALSE +FALSE != TRUE # TRUE # Missing data (NA) is logical, too -class(NA) # => [1] "logical" +class(NA) # "logical" + + # FACTORS # The factor class is for categorical data -# It has an attribute called levels that describes all the possible categories -factor("dog") -# => -# [1] dog -# Levels: dog -# (This will make more sense once we start talking about vectors) +# which can be ordered (like childrens' grade levels) +# or unordered (like gender) +levels(factor(c("female", "male", "male", "female", "NA", "female"))) # "female" "male" "NA" + +factor(c("female", "female", "male", "NA", "female")) +# female female male NA female +# Levels: female male NA + +data(infert) #Infertility after Spontaneous and Induced Abortion +levels(infert$education) # "0-5yrs" "6-11yrs" "12+ yrs" + + # VARIABLES @@ -80,8 +261,8 @@ y <- "1" # this is preferred TRUE -> z # this works but is weird # We can use coerce variables to different classes -as.numeric(y) # => [1] 1 -as.character(x) # => [1] "5" +as.numeric(y) # 1 +as.character(x) # "5" # LOOPS @@ -122,7 +303,7 @@ myFunc <- function(x) { } # Called like any other R function: -myFunc(5) # => [1] 19 +myFunc(5) # 19 ######################### # Fun with data: vectors, matrices, data frames, and arrays @@ -132,35 +313,35 @@ myFunc(5) # => [1] 19 # You can vectorize anything, so long as all components have the same type vec <- c(8, 9, 10, 11) -vec # => [1] 8 9 10 11 +vec # 8 9 10 11 # The class of a vector is the class of its components -class(vec) # => [1] "numeric" +class(vec) # "numeric" # If you vectorize items of different classes, weird coercions happen -c(TRUE, 4) # => [1] 1 4 -c("dog", TRUE, 4) # => [1] "dog" "TRUE" "4" +c(TRUE, 4) # 1 4 +c("dog", TRUE, 4) # "dog" "TRUE" "4" # We ask for specific components like so (R starts counting from 1) -vec[1] # => [1] 8 +vec[1] # 8 # We can also search for the indices of specific components, -which(vec %% 2 == 0) # => [1] 1 3 +which(vec %% 2 == 0) # 1 3 # or grab just the first or last entry in the vector -head(vec, 1) # => [1] 8 -tail(vec, 1) # => [1] 11 +head(vec, 1) # 8 +tail(vec, 1) # 11 # If an index "goes over" you'll get NA: -vec[6] # => [1] NA +vec[6] # NA # You can find the length of your vector with length() -length(vec) # => [1] 4 +length(vec) # 4 # You can perform operations on entire vectors or subsets of vectors -vec * 4 # => [1] 16 20 24 28 -vec[2:3] * 5 # => [1] 25 30 +vec * 4 # 16 20 24 28 +vec[2:3] * 5 # 25 30 # and there are many built-in functions to summarize vectors -mean(vec) # => [1] 9.5 -var(vec) # => [1] 1.666667 -sd(vec) # => [1] 1.290994 -max(vec) # => [1] 11 -min(vec) # => [1] 8 -sum(vec) # => [1] 38 +mean(vec) # 9.5 +var(vec) # 1.666667 +sd(vec) # 1.290994 +max(vec) # 11 +min(vec) # 8 +sum(vec) # 38 # TWO-DIMENSIONAL (ALL ONE CLASS) @@ -175,11 +356,11 @@ mat # Unlike a vector, the class of a matrix is "matrix", no matter what's in it class(mat) # => "matrix" # Ask for the first row -mat[1,] # => [1] 1 4 +mat[1,] # 1 4 # Perform operation on the first column -3 * mat[,1] # => [1] 3 6 9 +3 * mat[,1] # 3 6 9 # Ask for a specific cell -mat[3,2] # => [1] 6 +mat[3,2] # 6 # Transpose the whole matrix t(mat) # => @@ -196,7 +377,7 @@ mat2 # [2,] "2" "cat" # [3,] "3" "bird" # [4,] "4" "dog" -class(mat2) # => [1] matrix +class(mat2) # matrix # Again, note what happened! # Because matrices must contain entries all of the same class, # everything got converted to the character class @@ -216,7 +397,7 @@ mat3 # For columns of different classes, use the data frame dat <- data.frame(c(5,2,1,4), c("dog", "cat", "bird", "dog")) names(dat) <- c("number", "species") # name the columns -class(dat) # => [1] "data.frame" +class(dat) # "data.frame" dat # => # number species @@ -224,14 +405,14 @@ dat # 2 2 cat # 3 1 bird # 4 4 dog -class(dat$number) # => [1] "numeric" -class(dat[,2]) # => [1] "factor" +class(dat$number) # "numeric" +class(dat[,2]) # "factor" # The data.frame() function converts character vectors to factor vectors # There are many twisty ways to subset data frames, all subtly unalike -dat$number # => [1] 5 2 1 4 -dat[,1] # => [1] 5 2 1 4 -dat[,"number"] # => [1] 5 2 1 4 +dat$number # 5 2 1 4 +dat[,1] # 5 2 1 4 +dat[,"number"] # 5 2 1 4 # MULTI-DIMENSIONAL (ALL OF ONE CLASS) diff --git a/ruby.html.markdown b/ruby.html.markdown index 99817982..861a94ad 100644 --- a/ruby.html.markdown +++ b/ruby.html.markdown @@ -275,36 +275,36 @@ surround { puts 'hello world' } # Define a class with the class keyword class Human - # A class variable. It is shared by all instances of this class. - @@species = "H. sapiens" - - # Basic initializer - def initialize(name, age=0) - # Assign the argument to the "name" instance variable for the instance - @name = name - # If no age given, we will fall back to the default in the arguments list. - @age = age - end - - # Basic setter method - def name=(name) - @name = name - end - - # Basic getter method - def name - @name - end - - # A class method uses self to distinguish from instance methods. - # It can only be called on the class, not an instance. - def self.say(msg) - puts "#{msg}" - end - - def species - @@species - end + # A class variable. It is shared by all instances of this class. + @@species = "H. sapiens" + + # Basic initializer + def initialize(name, age=0) + # Assign the argument to the "name" instance variable for the instance + @name = name + # If no age given, we will fall back to the default in the arguments list. + @age = age + end + + # Basic setter method + def name=(name) + @name = name + end + + # Basic getter method + def name + @name + end + + # A class method uses self to distinguish from instance methods. + # It can only be called on the class, not an instance. + def self.say(msg) + puts "#{msg}" + end + + def species + @@species + end end diff --git a/scala.html.markdown b/scala.html.markdown index fef09404..b1b3ecbf 100644 --- a/scala.html.markdown +++ b/scala.html.markdown @@ -408,9 +408,11 @@ for(line <- Source.fromPath("myfile.txt").getLines()) [Scala for the impatient](http://horstmann.com/scala/) -[Twitter Scala school(http://twitter.github.io/scala_school/) +[Twitter Scala school](http://twitter.github.io/scala_school/) -[The scala documentation] +[The scala documentation](http://docs.scala-lang.org/) + +[Try Scala in your browser](http://scalatutorials.com/tour/) Join the [Scala user group](https://groups.google.com/forum/#!forum/scala-user) diff --git a/zh-cn/dart-cn.html.markdown b/zh-cn/dart-cn.html.markdown new file mode 100644 index 00000000..64663b21 --- /dev/null +++ b/zh-cn/dart-cn.html.markdown @@ -0,0 +1,498 @@ +--- +language: dart +filename: learndart.dart +contributors: + - ["Joao Pedrosa", "https://github.com/jpedrosa/"] +translators: + - ["Guokai Han", "https://github.com/hanguokai/"] +--- + +Dart 是编程语言王国的新人。 +它借鉴了许多其他主流语言，并且不会偏离它的兄弟语言 JavaScript 太多。 +就像 JavaScript 一样，Dart 的目标是提供良好的浏览器集成。 + +Dart 最有争议的特性必然是它的可选类型。 + +```javascript +import "dart:collection"; +import "dart:math" as DM; + +// 欢迎进入15分钟的 Dart 学习。 http://www.dartlang.org/ +// 这是一个可实际执行的向导。你可以用 Dart 运行它 +// 或者在线执行! 可以把代码复制/粘贴到这个网站。 http://try.dartlang.org/ + +// 函数声明和方法声明看起来一样。 +// 函数声明可以嵌套。声明使用这种 name() {} 的形式， +// 或者 name() => 单行表达式; 的形式。 +// 右箭头的声明形式会隐式地返回表达式的结果。 +example1() { + example1nested1() { + example1nested2() => print("Example1 nested 1 nested 2"); + example1nested2(); + } + example1nested1(); +} + +// 匿名函数没有函数名。 +example2() { + example2nested1(fn) { + fn(); + } + example2nested1(() => print("Example2 nested 1")); +} + +// 当声明函数类型的参数的时候，声明中可以包含 +// 函数参数需要的参数，指定所需的参数名即可。 +example3() { + example3nested1(fn(informSomething)) { + fn("Example3 nested 1"); + } + example3planB(fn) { // 或者不声明函数参数的参数 + fn("Example3 plan B"); + } + example3nested1((s) => print(s)); + example3planB((s) => print(s)); +} + +// 函数有可以访问到外层变量的闭包。 +var example4Something = "Example4 nested 1"; +example4() { + example4nested1(fn(informSomething)) { + fn(example4Something); + } + example4nested1((s) => print(s)); +} + +// 下面这个包含 sayIt 方法的类声明，同样有一个可以访问外层变量的闭包， +// 就像前面的函数一样。 +var example5method = "Example5 sayIt"; +class Example5Class { + sayIt() { + print(example5method); + } +} +example5() { + // 创建一个 Example5Class 类的匿名实例， + // 并调用它的 sayIt 方法。 + new Example5Class().sayIt(); +} + +// 类的声明使用这种形式 class name { [classBody] }. +// classBody 中可以包含实例方法和变量， +// 还可以包含类方法和变量。 +class Example6Class { + var example6InstanceVariable = "Example6 instance variable"; + sayIt() { + print(example6InstanceVariable); + } +} +example6() { + new Example6Class().sayIt(); +} + +// 类方法和变量使用 static 关键词声明。 +class Example7Class { + static var example7ClassVariable = "Example7 class variable"; + static sayItFromClass() { + print(example7ClassVariable); + } + sayItFromInstance() { + print(example7ClassVariable); + } +} +example7() { + Example7Class.sayItFromClass(); + new Example7Class().sayItFromInstance(); +} + +// 字面量非常方便，但是对于在函数/方法的外层的字面量有一个限制， +// 类的外层或外面的字面量必需是常量。 +// 字符串和数字默认是常量。 +// 但是 array 和 map 不是。他们需要用 "const" 声明为常量。 +var example8A = const ["Example8 const array"], + example8M = const {"someKey": "Example8 const map"}; +example8() { + print(example8A[0]); + print(example8M["someKey"]); +} + +// Dart 中的循环使用标准的 for () {} 或 while () {} 的形式， +// 以及更加现代的 for (.. in ..) {} 的形式, 或者 +// 以 forEach 开头并具有许多特性支持的函数回调的形式。 +var example9A = const ["a", "b"]; +example9() { + for (var i = 0; i < example9A.length; i++) { + print("Example9 for loop '${example9A[i]}'"); + } + var i = 0; + while (i < example9A.length) { + print("Example9 while loop '${example9A[i]}'"); + i++; + } + for (var e in example9A) { + print("Example9 for-in loop '${e}'"); + } + example9A.forEach((e) => print("Example9 forEach loop '${e}'")); +} + +// 遍历字符串中的每个字符或者提取其子串。 +var example10S = "ab"; +example10() { + for (var i = 0; i < example10S.length; i++) { + print("Example10 String character loop '${example10S[i]}'"); + } + for (var i = 0; i < example10S.length; i++) { + print("Example10 substring loop '${example10S.substring(i, i + 1)}'"); + } +} + +// 支持两种数字格式 int 和 double 。 +example11() { + var i = 1 + 320, d = 3.2 + 0.01; + print("Example11 int ${i}"); + print("Example11 double ${d}"); +} + +// DateTime 提供了日期/时间的算法。 +example12() { + var now = new DateTime.now(); + print("Example12 now '${now}'"); + now = now.add(new Duration(days: 1)); + print("Example12 tomorrow '${now}'"); +} + +// 支持正则表达式。 +example13() { + var s1 = "some string", s2 = "some", re = new RegExp("^s.+?g\$"); + match(s) { + if (re.hasMatch(s)) { + print("Example13 regexp matches '${s}'"); + } else { + print("Example13 regexp doesn't match '${s}'"); + } + } + match(s1); + match(s2); +} + +// 布尔表达式必需被解析为 true 或 false， +// 因为不支持隐式转换。 +example14() { + var v = true; + if (v) { + print("Example14 value is true"); + } + v = null; + try { + if (v) { + // 不会执行 + } else { + // 不会执行 + } + } catch (e) { + print("Example14 null value causes an exception: '${e}'"); + } +} + +// try/catch/finally 和 throw 语句用于异常处理。 +// throw 语句可以使用任何对象作为参数。 +example15() { + try { + try { + throw "Some unexpected error."; + } catch (e) { + print("Example15 an exception: '${e}'"); + throw e; // Re-throw + } + } catch (e) { + print("Example15 catch exception being re-thrown: '${e}'"); + } finally { + print("Example15 Still run finally"); + } +} + +// 要想有效地动态创建长字符串， +// 应该使用 StringBuffer。 或者 join 一个字符串的数组。 +example16() { + var sb = new StringBuffer(), a = ["a", "b", "c", "d"], e; + for (e in a) { sb.write(e); } + print("Example16 dynamic string created with " + "StringBuffer '${sb.toString()}'"); + print("Example16 join string array '${a.join()}'"); +} + +// 字符串连接只需让相邻的字符串字面量挨着， +// 不需要额外的操作符。 +example17() { + print("Example17 " + "concatenate " + "strings " + "just like that"); +} + +// 字符串使用单引号或双引号做分隔符，二者并没有实际的差异。 +// 这种灵活性可以很好地避免内容中需要转义分隔符的情况。 +// 例如，字符串内容里的 HTML 属性使用了双引号。 +example18() { + print('Example18 <a href="etc">' + "Don't can't I'm Etc" + '</a>'); +} + +// 用三个单引号或三个双引号表示的字符串 +// 可以跨越多行，并且包含行分隔符。 +example19() { + print('''Example19 <a href="etc"> +Example19 Don't can't I'm Etc +Example19 </a>'''); +} + +// 字符串可以使用 $ 字符插入内容。 +// 使用 $ { [expression] } 的形式，表达式的值会被插入到字符串中。 +// $ 跟着一个变量名会插入变量的值。 +// 如果要在字符串中插入 $ ，可以使用 \$ 的转义形式代替。 +example20() { + var s1 = "'\${s}'", s2 = "'\$s'"; + print("Example20 \$ interpolation ${s1} or $s2 works."); +} + +// 可选类型允许作为 API 的标注，并且可以辅助 IDE， +// 这样 IDE 可以更好地提供重构、自动完成和错误检测功能。 +// 目前为止我们还没有声明任何类型，并且程序运行地很好。 +// 事实上，类型在运行时会被忽略。 +// 类型甚至可以是错的，并且程序依然可以执行， +// 好像和类型完全无关一样。 +// 有一个运行时参数可以让程序进入检查模式，它会在运行时检查类型错误。 +// 这在开发时很有用，但是由于增加了额外的检查会使程序变慢， +// 因此应该避免在部署时使用。 +class Example21 { + List<String> _names; + Example21() { + _names = ["a", "b"]; + } + List<String> get names => _names; + set names(List<String> list) { + _names = list; + } + int get length => _names.length; + void add(String name) { + _names.add(name); + } +} +void example21() { + Example21 o = new Example21(); + o.add("c"); + print("Example21 names '${o.names}' and length '${o.length}'"); + o.names = ["d", "e"]; + print("Example21 names '${o.names}' and length '${o.length}'"); +} + +// 类的继承形式是 class name extends AnotherClassName {} 。 +class Example22A { + var _name = "Some Name!"; + get name => _name; +} +class Example22B extends Example22A {} +example22() { + var o = new Example22B(); + print("Example22 class inheritance '${o.name}'"); +} + +// 类也可以使用 mixin 的形式 ： +// class name extends SomeClass with AnotherClassName {}. +// 必需继承某个类才能 mixin 另一个类。 +// 当前 mixin 的模板类不能有构造函数。 +// Mixin 主要是用来和辅助的类共享方法的， +// 这样单一继承就不会影响代码复用。 +// Mixin 声明在类定义的 "with" 关键词后面。 +class Example23A {} +class Example23Utils { + addTwo(n1, n2) { + return n1 + n2; + } +} +class Example23B extends Example23A with Example23Utils { + addThree(n1, n2, n3) { + return addTwo(n1, n2) + n3; + } +} +example23() { + var o = new Example23B(), r1 = o.addThree(1, 2, 3), + r2 = o.addTwo(1, 2); + print("Example23 addThree(1, 2, 3) results in '${r1}'"); + print("Example23 addTwo(1, 2) results in '${r2}'"); +} + +// 类的构造函数名和类名相同，形式为 +// SomeClass() : super() {}, 其中 ": super()" 的部分是可选的， +// 它用来传递参数给父类的构造函数。 +class Example24A { + var _value; + Example24A({value: "someValue"}) { + _value = value; + } + get value => _value; +} +class Example24B extends Example24A { + Example24B({value: "someOtherValue"}) : super(value: value); +} +example24() { + var o1 = new Example24B(), + o2 = new Example24B(value: "evenMore"); + print("Example24 calling super during constructor '${o1.value}'"); + print("Example24 calling super during constructor '${o2.value}'"); +} + +// 对于简单的类，有一种设置构造函数参数的快捷方式。 +// 只需要使用 this.parameterName 的前缀， +// 它就会把参数设置为同名的实例变量。 +class Example25 { + var value, anotherValue; + Example25({this.value, this.anotherValue}); +} +example25() { + var o = new Example25(value: "a", anotherValue: "b"); + print("Example25 shortcut for constructor '${o.value}' and " + "'${o.anotherValue}'"); +} + +// 可以在大括号 {} 中声明命名参数。 +// 大括号 {} 中声明的参数的顺序是随意的。 +// 在中括号 [] 中声明的参数也是可选的。 +example26() { + var _name, _surname, _email; + setConfig1({name, surname}) { + _name = name; + _surname = surname; + } + setConfig2(name, [surname, email]) { + _name = name; + _surname = surname; + _email = email; + } + setConfig1(surname: "Doe", name: "John"); + print("Example26 name '${_name}', surname '${_surname}', " + "email '${_email}'"); + setConfig2("Mary", "Jane"); + print("Example26 name '${_name}', surname '${_surname}', " + "email '${_email}'"); +} + +// 使用 final 声明的变量只能被设置一次。 +// 在类里面，final 实例变量可以通过常量的构造函数参数设置。 +class Example27 { + final color1, color2; + // 更灵活一点的方法是在冒号 : 后面设置 final 实例变量。 + Example27({this.color1, color2}) : color2 = color2; +} +example27() { + final color = "orange", o = new Example27(color1: "lilac", color2: "white"); + print("Example27 color is '${color}'"); + print("Example27 color is '${o.color1}' and '${o.color2}'"); +} + +// 要导入一个库，使用 import "libraryPath" 的形式，或者如果要导入的是 +// 核心库使用 import "dart:libraryName" 。还有一个称为 "pub" 的包管理工具， +// 它使用 import "package:packageName" 的约定形式。 +// 看下这个文件顶部的 import "dart:collection"; 语句。 +// 导入语句必需在其它代码声明之前出现。IterableBase 来自于 dart:collection 。 +class Example28 extends IterableBase { + var names; + Example28() { + names = ["a", "b"]; + } + get iterator => names.iterator; +} +example28() { + var o = new Example28(); + o.forEach((name) => print("Example28 '${name}'")); +} + +// 对于控制流语句，我们有： +// * 必需带 break 的标准 switch 语句 +// * if-else 和三元操作符 ..?..:.. +// * 闭包和匿名函数 +// * break, continue 和 return 语句 +example29() { + var v = true ? 30 : 60; + switch (v) { + case 30: + print("Example29 switch statement"); + break; + } + if (v < 30) { + } else if (v > 30) { + } else { + print("Example29 if-else statement"); + } + callItForMe(fn()) { + return fn(); + } + rand() { + v = new DM.Random().nextInt(50); + return v; + } + while (true) { + print("Example29 callItForMe(rand) '${callItForMe(rand)}'"); + if (v != 30) { + break; + } else { + continue; + } + // 不会到这里。 + } +} + +// 解析 int，把 double 转成 int，或者使用 ~/ 操作符在除法计算时仅保留整数位。 +// 让我们也来场猜数游戏吧。 +example30() { + var gn, tooHigh = false, + n, n2 = (2.0).toInt(), top = int.parse("123") ~/ n2, bottom = 0; + top = top ~/ 6; + gn = new DM.Random().nextInt(top + 1); // +1 because nextInt top is exclusive + print("Example30 Guess a number between 0 and ${top}"); + guessNumber(i) { + if (n == gn) { + print("Example30 Guessed right! The number is ${gn}"); + } else { + tooHigh = n > gn; + print("Example30 Number ${n} is too " + "${tooHigh ? 'high' : 'low'}. Try again"); + } + return n == gn; + } + n = (top - bottom) ~/ 2; + while (!guessNumber(n)) { + if (tooHigh) { + top = n - 1; + } else { + bottom = n + 1; + } + n = bottom + ((top - bottom) ~/ 2); + } +} + +// 程序的唯一入口点是 main 函数。 +// 在程序开始执行 main 函数之前，不期望执行任何外层代码。 +// 这样可以帮助程序更快地加载，甚至仅惰性加载程序启动时需要的部分。 +main() { + print("Learn Dart in 15 minutes!"); + [example1, example2, example3, example4, example5, example6, example7, + example8, example9, example10, example11, example12, example13, example14, + example15, example16, example17, example18, example19, example20, + example21, example22, example23, example24, example25, example26, + example27, example28, example29, example30 + ].forEach((ef) => ef()); +} + +``` + +## 延伸阅读 + +Dart 有一个综合性网站。它涵盖了 API 参考、入门向导、文章以及更多， +还包括一个有用的在线试用 Dart 页面。 +http://www.dartlang.org/ +http://try.dartlang.org/ + + + |