diff options
| -rw-r--r-- | c.html.markdown | 250 | ||||
| -rw-r--r-- | ko-kr/java-kr.html.markdown | 10 | ||||
| -rw-r--r-- | pt-br/ruby-pt.html.markdown | 8 | ||||
| -rw-r--r-- | ru-ru/clojure-ru.html.markdown | 2 | ||||
| -rw-r--r-- | ru-ru/php-ru.html.markdown | 18 | ||||
| -rw-r--r-- | ru-ru/python-ru.html.markdown | 8 | ||||
| -rw-r--r-- | zh-cn/go-zh.html.markdown | 183 |
7 files changed, 240 insertions, 239 deletions
diff --git a/c.html.markdown b/c.html.markdown index 00b13cb0..24a96463 100644 --- a/c.html.markdown +++ b/c.html.markdown @@ -1,11 +1,9 @@ --- -- name: c -- category: language -- language: c -- filename: learnc.c -- contributors: - - [Adam Bard](http://adambard.com/) - - [Árpád Goretity](http://twitter.com/H2CO3_iOS) +language: c +filename: learnc.c +contributors: + - ["Adam Bard", "http://adambard.com/"] + - ["Árpád Goretity", "http://twitter.com/H2CO3_iOS"] --- @@ -27,17 +25,10 @@ Multi-line comments look like this. They work in C89 as well. #include <stdio.h> #include <string.h> -// file names between <angle brackets> are headers from the C standard library. -// They are searched for by the preprocessor in the system include paths -// (usually /usr/lib on Unices, can be controlled with the -I<dir> option if you are using GCC or clang.) +// (File names between <angle brackets> are headers from the C standard library.) // For your own headers, use double quotes instead of angle brackets: #include "my_header.h" -// The C preprocessor introduces an almost fully-featured macro language. It's useful, but -// it can be confusing (and what's even worse, it can be misused). Read the -// Wikipedia article on the C preprocessor for further information: -// http://en.wikipedia.org/wiki/C_preprocessor - // Declare function signatures in advance in a .h file, or at the top of // your .c file. void function_1(); @@ -50,132 +41,117 @@ int main() { // %d is an integer, \n is a newline printf("%d\n", 0); // => Prints 0 // All statements must end with a semicolon - + /////////////////////////////////////// // Types /////////////////////////////////////// - - // You have to declare variables before using them. A variable declaration - // requires you to specify its type; a variable's type determines its size - // in bytes. - + // ints are usually 4 bytes int x_int = 0; - + // shorts are usually 2 bytes short x_short = 0; - + // chars are guaranteed to be 1 byte char x_char = 0; char y_char = 'y'; // Char literals are quoted with '' - + // longs are often 4 to 8 bytes; long longs are guaranteed to be at least // 64 bits long x_long = 0; long long x_long_long = 0; - + // floats are usually 32-bit floating point numbers float x_float = 0.0; - + // doubles are usually 64-bit floating-point numbers double x_double = 0.0; - - // Integral types may be unsigned. This means they can't be negative, but - // the maximum value of an unsigned variable is greater than the maximum - // signed value of the same size. - unsigned char ux_char; + + // Integral types may be unsigned. unsigned short ux_short; unsigned int ux_int; unsigned long long ux_long_long; - - // Other than char, which is always 1 byte (but not necessarily 8 bits!), - // these types vary in size depending on your machine and compiler. - // sizeof(T) gives you the size of a variable with type T in - // bytes so you can express the size of these types in a portable way. - // sizeof(obj) yields the size of an actual expression (variable, literal, etc.). - // For example, + + // sizeof(T) gives you the size of a variable with type T in bytes + // sizeof(obj) yields the size of the expression (variable, literal, etc.). printf("%zu\n", sizeof(int)); // => 4 (on most machines with 4-byte words) - - - // It's worth noting that if the argument of the `sizeof` operator is not a type but an expression, - // then its argument is not evaluated except VLAs (see below). Also, `sizeof()` is an operator, not a function, - // furthermore, the value it yields is a compile-time constant (except when used on VLAs, again.) + + + // If the argument of the `sizeof` operator an expression, then its argument + // is not evaluated (except VLAs (see below)). + // The value it yields in this case is a compile-time constant. int a = 1; size_t size = sizeof(a++); // a++ is not evaluated printf("sizeof(a++) = %zu where a = %d\n", size, a); - // the above code prints "sizeof(a++) = 4 where a = 1" (on a usual 32-bit architecture) - + // prints "sizeof(a++) = 4 where a = 1" (on a 32-bit architecture) + // Arrays must be initialized with a concrete size. char my_char_array[20]; // This array occupies 1 * 20 = 20 bytes int my_int_array[20]; // This array occupies 4 * 20 = 80 bytes // (assuming 4-byte words) - - + + // You can initialize an array to 0 thusly: char my_array[20] = {0}; - + // Indexing an array is like other languages -- or, // rather, other languages are like C my_array[0]; // => 0 - + // Arrays are mutable; it's just memory! my_array[1] = 2; printf("%d\n", my_array[1]); // => 2 - - // In C99 (and as an optional feature in C11), variable-length arrays (VLAs) can be declared as well. - // The size of such an array need not be a compile time constant: + + // In C99 (and as an optional feature in C11), variable-length arrays (VLAs) + // can be declared as well. The size of such an array need not be a compile + // time constant: printf("Enter the array size: "); // ask the user for an array size char buf[0x100]; fgets(buf, sizeof buf, stdin); - size_t size = strtoul(buf, NULL, 10); // strtoul parses a string to an unsigned integer + + // strtoul parses a string to an unsigned integer + size_t size = strtoul(buf, NULL, 10); int var_length_array[size]; // declare the VLA printf("sizeof array = %zu\n", sizeof var_length_array); - + // A possible outcome of this program may be: - Enter the array size: 10 - sizeof array = 40 - + // > Enter the array size: 10 + // > sizeof array = 40 + // Strings are just arrays of chars terminated by a NUL (0x00) byte, // represented in strings as the special character '\0'. // (We don't have to include the NUL byte in string literals; the compiler // inserts it at the end of the array for us.) char a_string[20] = "This is a string"; printf("%s\n", a_string); // %s formats a string - - /* - You may have noticed that a_string is only 16 chars long. - Char #17 is the NUL byte. - Chars #18, 19 and 20 are 0 as well - if an initializer list (in this case, the string literal) - has less elements than the array it is initializing, then excess array elements are implicitly - initialized to zero. This is why int ar[10] = { 0 } works as expected intuitively. - */ - + printf("%d\n", a_string[16]); // => 0 - - // So string literals are strings enclosed within double quotes, but if we have characters - // between single quotes, that's a character literal. + // i.e., byte #17 is 0 (as are 18, 19, and 20) + + // If we have characters between single quotes, that's a character literal. // It's of type `int`, and *not* `char` (for historical reasons). int cha = 'a'; // fine - char chb = 'a'; // fine too (implicit conversion from int to char - truncation) - + char chb = 'a'; // fine too (implicit conversion from int to char) + /////////////////////////////////////// // Operators /////////////////////////////////////// - + int i1 = 1, i2 = 2; // Shorthand for multiple declaration float f1 = 1.0, f2 = 2.0; - + // Arithmetic is straightforward i1 + i2; // => 3 i2 - i1; // => 1 i2 * i1; // => 2 i1 / i2; // => 0 (0.5, but truncated towards 0) - - f1 / f2; // => 0.5, plus or minus epsilon - floating-point numbers and calculations are not exact - + + f1 / f2; // => 0.5, plus or minus epsilon + // Floating-point numbers and calculations are not exact + // Modulo is there as well 11 % 3; // => 2 - + // Comparison operators are probably familiar, but // there is no boolean type in c. We use ints instead. // (Or _Bool or bool in C99.) @@ -187,14 +163,14 @@ int main() { 3 < 2; // => 0 2 <= 2; // => 1 2 >= 2; // => 1 - + // C is not Python - comparisons don't chain. int a = 1; // WRONG: int between_0_and_2 = 0 < a < 2; // Correct: int between_0_and_2 = 0 < a && a < 2; - + // Logic works on ints !3; // => 0 (Logical not) !0; // => 1 @@ -202,7 +178,7 @@ int main() { 0 && 1; // => 0 0 || 1; // => 1 (Logical or) 0 || 0; // => 0 - + // Bitwise operators! ~0x0F; // => 0xF0 (bitwise negation, "1's complement") 0x0F & 0xF0; // => 0x00 (bitwise AND) @@ -210,17 +186,17 @@ int main() { 0x04 ^ 0x0F; // => 0x0B (bitwise XOR) 0x01 << 1; // => 0x02 (bitwise left shift (by 1)) 0x02 >> 1; // => 0x01 (bitwise right shift (by 1)) - - // Be careful when shifting signed integers - the following are all undefined behavior: + + // Be careful when shifting signed integers - the following are undefined: // - shifting into the sign bit of a signed integer (int a = 1 << 32) // - left-shifting a negative number (int a = -1 << 2) - // - shifting by an offset which is more than or equal to the width of the type of the LHS: + // - shifting by an offset which is >= the width of the type of the LHS: // int a = 1 << 32; // UB if int is 32 bits wide - + /////////////////////////////////////// // Control Structures /////////////////////////////////////// - + if (0) { printf("I am never run\n"); } else if (0) { @@ -228,36 +204,38 @@ int main() { } else { printf("I print\n"); } - + // While loops exist int ii = 0; while (ii < 10) { - printf("%d, ", ii++); // ii++ increments ii in-place, after yielding its value ("postincrement"). + printf("%d, ", ii++); // ii++ increments ii in-place + // after yielding its value ("postincrement"). } // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, " - + printf("\n"); - + int kk = 0; do { printf("%d, ", kk); - } while (++kk < 10); // ++kk increments kk in-place, and yields the already incremented value ("preincrement") + } while (++kk < 10); // ++kk increments kk in-place, and yields + // the already incremented value ("preincrement") // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, " - + printf("\n"); - + // For loops too int jj; for (jj=0; jj < 10; jj++) { printf("%d, ", jj); } // => prints "0, 1, 2, 3, 4, 5, 6, 7, 8, 9, " - + printf("\n"); - + // branching with multiple choices: switch() switch (some_integral_expression) { case 0: // labels need to be integral *constant* epxressions do_stuff(); - break; // if you don't break, control flow falls over labels - you usually don't want that. + break; // if you don't break, control flow falls over labels case 1: do_something_else(); break; @@ -267,73 +245,74 @@ int main() { exit(-1); break; } - + /////////////////////////////////////// // Typecasting /////////////////////////////////////// - + // Every value in C has a type, but you can cast one value into another type // if you want (with some constraints). - + int x_hex = 0x01; // You can assign vars with hex literals - + // Casting between types will attempt to preserve their numeric values printf("%d\n", x_hex); // => Prints 1 printf("%d\n", (short) x_hex); // => Prints 1 printf("%d\n", (char) x_hex); // => Prints 1 - + // Types will overflow without warning printf("%d\n", (unsigned char) 257); // => 1 (Max char = 255 if char is 8 bits long) - // printf("%d\n", (unsigned char) 257); would be undefined behavior - `char' is usually signed - // on most modern systems, and signed integer overflow invokes UB. - // Also, for determining the maximal value of a `char`, a `signed char` and an `unisigned char`, + + // For determining the max value of a `char`, a `signed char` and an `unisigned char`, // respectively, use the CHAR_MAX, SCHAR_MAX and UCHAR_MAX macros from <limits.h> - + // Integral types can be cast to floating-point types, and vice-versa. printf("%f\n", (float)100); // %f formats a float printf("%lf\n", (double)100); // %lf formats a double printf("%d\n", (char)100.0); - + /////////////////////////////////////// // Pointers /////////////////////////////////////// - + // A pointer is a variable declared to store a memory address. Its declaration will // also tell you the type of data it points to. You can retrieve the memory address // of your variables, then mess with them. - + int x = 0; printf("%p\n", (void *)&x); // Use & to retrieve the address of a variable // (%p formats an object pointer of type void *) // => Prints some address in memory; - - + + // Pointers start with * in their declaration int *px, not_a_pointer; // px is a pointer to an int px = &x; // Stores the address of x in px printf("%p\n", (void *)px); // => Prints some address in memory printf("%zu, %zu\n", sizeof(px), sizeof(not_a_pointer)); // => Prints "8, 4" on a typical 64-bit system - + // To retreive the value at the address a pointer is pointing to, // put * in front to de-reference it. - // Note: yes, it may be confusing that '*' is used for _both_ declaring a pointer and dereferencing it. - printf("%d\n", *px); // => Prints 0, the value of x, which is what px is pointing to the address of - + // Note: yes, it may be confusing that '*' is used for _both_ declaring a + // pointer and dereferencing it. + printf("%d\n", *px); // => Prints 0, the value of x + // You can also change the value the pointer is pointing to. // We'll have to wrap the de-reference in parenthesis because // ++ has a higher precedence than *. (*px)++; // Increment the value px is pointing to by 1 printf("%d\n", *px); // => Prints 1 printf("%d\n", x); // => Prints 1 - - int x_array[20]; // Arrays are a good way to allocate a contiguous block of memory + + // Arrays are a good way to allocate a contiguous block of memory + int x_array[20]; int xx; for (xx = 0; xx < 20; xx++) { x_array[xx] = 20 - xx; } // Initialize x_array to 20, 19, 18,... 2, 1 - + // Declare a pointer of type int and initialize it to point to x_array int* x_ptr = x_array; // x_ptr now points to the first element in the array (the integer 20). @@ -342,50 +321,52 @@ int main() { // it decays into (implicitly converted to) a pointer. // Exceptions: when the array is the argument of the `&` (address-od) operator: int arr[10]; - int (*ptr_to_arr)[10] = &arr; // &arr is NOT of type `int *`! It's of type "pointer to array" (of ten `int`s). + int (*ptr_to_arr)[10] = &arr; // &arr is NOT of type `int *`! + // It's of type "pointer to array" (of ten `int`s). // or when the array is a string literal used for initializing a char array: char arr[] = "foobarbazquirk"; // or when it's the argument of the `sizeof` or `alignof` operator: int arr[10]; int *ptr = arr; // equivalent with int *ptr = &arr[0]; printf("%zu %zu\n", sizeof arr, sizeof ptr); // probably prints "40, 4" or "40, 8" - + // Pointers are incremented and decremented based on their type // (this is called pointer arithmetic) printf("%d\n", *(x_ptr + 1)); // => Prints 19 printf("%d\n", x_array[1]); // => Prints 19 - + // You can also dynamically allocate contiguous blocks of memory with the // standard library function malloc, which takes one argument of type size_t // representing the number of bytes to allocate (usually from the heap, although this // may not be true on e. g. embedded systems - the C standard says nothing about it). int *my_ptr = malloc(sizeof(*my_ptr) * 20); for (xx = 0; xx < 20; xx++) { - *(my_ptr + xx) = 20 - xx; // my_ptr[xx] = 20-xx would also work here, and it's also more readable + *(my_ptr + xx) = 20 - xx; // my_ptr[xx] = 20-xx } // Initialize memory to 20, 19, 18, 17... 2, 1 (as ints) - + // Dereferencing memory that you haven't allocated gives // "unpredictable results" - the program is said to invoke "undefined behavior" printf("%d\n", *(my_ptr + 21)); // => Prints who-knows-what? It may even crash. - + // When you're done with a malloc'd block of memory, you need to free it, // or else no one else can use it until your program terminates // (this is called a "memory leak"): free(my_ptr); - + // Strings are arrays of char, but they are usually represented as a // pointer-to-char (which is a pointer to the first element of the array). // It's good practice to use `const char *' when referring to a string literal, // since string literals shall not be modified (i. e. "foo"[0] = 'a' is ILLEGAL.) const char *my_str = "This is my very own string literal"; printf("%c\n", *my_str); // => 'T' - - // This is not the case if the string is an array (potentially initialized with a string literal) + + // This is not the case if the string is an array + // (potentially initialized with a string literal) // that resides in writable memory, as in: char foo[] = "foo"; foo[0] = 'a'; // this is legal, foo now contains "aoo" - + function_1(); } // end main function @@ -435,17 +416,17 @@ printf("%s\n", c); // => ".tset a si sihT" typedef int my_type; my_type my_type_var = 0; -// Structs are just collections of data, the members are allocated sequentially, in the order they are written: +// Structs are just collections of data, the members are allocated sequentially, +// in the order they are written: struct rectangle { int width; int height; }; -// it's generally not true that sizeof(struct rectangle) == sizeof(int) + sizeof(int) due to -// potential padding between the structure members (this is for alignment reasons. Probably won't -// happen if all members are of the same type, but watch out! -// See http://stackoverflow.com/questions/119123/why-isnt-sizeof-for-a-struct-equal-to-the-sum-of-sizeof-of-each-member -// for further information. +// It's not generally true that +// sizeof(struct rectangle) == sizeof(int) + sizeof(int) +// due to potential padding between the structure members (this is for alignment +// reasons). [1] void function_1() { @@ -473,7 +454,8 @@ int area(rect r) return r.width * r.height; } -// if you have large structs, you can pass them "by pointer" to avoid copying the whole struct: +// if you have large structs, you can pass them "by pointer" to avoid copying +// the whole struct: int area(const rect *r) { return r->width * r->height; @@ -527,3 +509,5 @@ Readable code is better than clever code and fast code. For a good, sane coding [Linux kernel coding stlye](https://www.kernel.org/doc/Documentation/CodingStyle). Other than that, Google is your friend. + +[1] http://stackoverflow.com/questions/119123/why-isnt-sizeof-for-a-struct-equal-to-the-sum-of-sizeof-of-each-member diff --git a/ko-kr/java-kr.html.markdown b/ko-kr/java-kr.html.markdown index dcca9b2e..371b4665 100644 --- a/ko-kr/java-kr.html.markdown +++ b/ko-kr/java-kr.html.markdown @@ -1,5 +1,6 @@ --- language: java +filename: java-kr.java category: language contributors: - ["Jake Prather", "http://github.com/JakeHP"] @@ -26,7 +27,8 @@ import java.util.ArrayList; // java.security 패키지 안에 있는 모든 클래스를 임포트합니다. import java.security.*; -// 각 .java 파일에는 공용(public) 클래스가 들어 있으며, 클래스의 이름은 파일명과 동일합니다. +// 각 .java 파일에는 공용(public) 클래스가 들어 있으며, 클래스의 이름은 +// 파일명과 동일합니다. public class LearnJava { // 프로그램에는 반드시 진입점 역할을 하는 main 메서드가 하나 있어야 합니다. @@ -253,8 +255,8 @@ public class LearnJava { // String // 형변환 - // 자바 객채 또한 형변환할 수 있으며, 이와 관련해서 알아야 할 세부사항이 많을뿐더러 - // 다소 중급 수준에 해당하는 개념들도 다뤄야 합니다. + // 자바 객채 또한 형변환할 수 있으며, 이와 관련해서 알아야 할 세부사항이 + // 많을뿐더러 다소 중급 수준에 해당하는 개념들도 다뤄야 합니다. // 이와 관련된 사항은 아래 링크를 참고하세요. // http://docs.oracle.com/javase/tutorial/java/IandI/subclasses.html @@ -403,4 +405,4 @@ class PennyFarthing extends Bicycle { * [제네릭(Generics)](http://docs.oracle.com/javase/tutorial/java/generics/index.html) -* [자바 코딩 관례(Java Code Conventions)](http://www.oracle.com/technetwork/java/codeconv-138413.html)
\ No newline at end of file +* [자바 코딩 관례(Java Code Conventions)](http://www.oracle.com/technetwork/java/codeconv-138413.html) diff --git a/pt-br/ruby-pt.html.markdown b/pt-br/ruby-pt.html.markdown index 8e8ce6a8..484bb0dd 100644 --- a/pt-br/ruby-pt.html.markdown +++ b/pt-br/ruby-pt.html.markdown @@ -1,5 +1,6 @@ --- language: ruby +lang: br-pt filename: learnruby.rb contributors: - ["Bruno Henrique - Garu", "http://garulab.com"] @@ -98,9 +99,10 @@ caminho_para_a_raiz_do_projeto = '/bom/nome/' caminho = '/nome/ruim/' # Símbolos (são objetos) -# Símbolos são imutáveis, são constantes reutilizáveis representadadas internamente por um -# valor inteiro. Eles são frequentemente usados no lugar de strings para transmitir com eficiência os valores -# específicos e significativos +# Símbolos são imutáveis, são constantes reutilizáveis representadadas +# internamente por um valor inteiro. Eles são frequentemente usados no +# lugar de strings para transmitir com eficiência os valores específicos +# e significativos :pendente.class #=> Symbol diff --git a/ru-ru/clojure-ru.html.markdown b/ru-ru/clojure-ru.html.markdown index 48c16192..e1d68e5a 100644 --- a/ru-ru/clojure-ru.html.markdown +++ b/ru-ru/clojure-ru.html.markdown @@ -4,7 +4,7 @@ filename: learnclojure-ru.clj contributors: - ["Adam Bard", "http://adambard.com/"] - ["Alexey Pirogov", "http://twitter.com/alex_pir"] - +lang: ru-ru --- Clojure, это представитель семейства Lisp-подобных языков, разработанный diff --git a/ru-ru/php-ru.html.markdown b/ru-ru/php-ru.html.markdown index 6c5720e3..9133ecca 100644 --- a/ru-ru/php-ru.html.markdown +++ b/ru-ru/php-ru.html.markdown @@ -88,7 +88,8 @@ $unescaped = 'This just contains a slash and a t: \t'; // Заключайте переменные в фигурные скобки если это необходимо $money = "I have $${number} in the bank."; -// Начиная с PHP 5.3, синтаксис nowdocs может использоваться для неинтерполированного многострочного текста +// Начиная с PHP 5.3, синтаксис nowdocs может использоваться для +// неинтерполированного многострочного текста $nowdoc = <<<'END' Multi line string @@ -210,11 +211,13 @@ echo $integer + $integer; // => 2 $string = '1'; echo $string + $string; // => 2 (строка превращается в число) -// Выводится 0 по той причине, что оператор + не может привести строку 'one' к числовому типу +// Выводится 0 по той причине, что оператор + не может привести строку 'one' к +// числовому типу $string = 'one'; echo $string + $string; // => 0 -// Приведение типов (type casting) может быть использовано для преобразование переменной в другой тип +// Приведение типов (type casting) может быть использовано для преобразование +// переменной в другой тип $boolean = (boolean) 1; // => true $zero = 0; @@ -429,10 +432,11 @@ return 'Anything you like.'; // Эти функции могут также возвращать значения. $value = include 'my-include.php'; -// Имена файлов содержат их путь в файловой системе, или если передано просто имя файла, -// PHP обращается к директиве include_path. Если файл не найден в include_path, предпринимается -// попытка поиска в папке, где выполняется скрипт или в текущей рабочей директории. -// Если не в одном из этих мест файл не найден - выдается ошибка +// Имена файлов содержат их путь в файловой системе, или если передано просто +// имя файла, PHP обращается к директиве include_path. Если файл не найден в +// include_path, предпринимается попытка поиска в папке, где выполняется скрипт +// или в текущей рабочей директории. Если не в одном из этих мест файл не +// найден - выдается ошибка /* */ /******************************** diff --git a/ru-ru/python-ru.html.markdown b/ru-ru/python-ru.html.markdown index 58b0adcc..9163c8aa 100644 --- a/ru-ru/python-ru.html.markdown +++ b/ru-ru/python-ru.html.markdown @@ -1,5 +1,6 @@ --- language: python +lang: ru-ru contributors: - ["Yury Timofeev", "http://twitter.com/gagar1n"] filename: learnpython-ru.py @@ -219,7 +220,8 @@ filled_dict["four"] # KeyError # Чтобы избежать этого, используйте метод get filled_dict.get("one") #=> 1 filled_dict.get("four") #=> None -# Метод get также принимает аргумент default, значение которого будет возвращено при отсутствии указанного ключа +# Метод get также принимает аргумент default, значение которого будет +# возвращено при отсутствии указанного ключа filled_dict.get("one", 4) #=> 1 filled_dict.get("four", 4) #=> 4 @@ -314,7 +316,9 @@ try: # Для выбора ошибки используется raise raise IndexError("Это IndexError") except IndexError as e: - pass # pass это просто отсутствие оператора. Обычно здесь происходит восстановление от ошибки. + # pass это просто отсутствие оператора. Обычно здесь происходит + # восстановление от ошибки. + pass #################################################### diff --git a/zh-cn/go-zh.html.markdown b/zh-cn/go-zh.html.markdown index 25fd1f03..8f7cb2af 100644 --- a/zh-cn/go-zh.html.markdown +++ b/zh-cn/go-zh.html.markdown @@ -29,7 +29,8 @@ import ( "strconv" // 字符串转换 ) -//函数声明：Main是程序执行的入口。不管你喜欢还是不喜欢，反正G就用了花括号来包住函数体。 +// 函数声明：Main是程序执行的入口。 +// 不管你喜欢还是不喜欢，反正G就用了花括号来包住函数体。 func main() { // 往标准输出打印一行。 // 用包名fmt限制打印函数。 @@ -65,10 +66,10 @@ func learnTypes() { can include line breaks.` // 同样是String类型 // 非ascii字符。Go使用UTF-8编码。 - g := 'Σ' // rune类型，uint32的别名，使用UTF-8编码 + g := 'Σ' // rune类型，uint32的别名，使用UTF-8编码 - f := 3.14195 // float64类型，IEEE-754 64位浮点数 - c := 3 + 4i // complex128类型，内部使用两个float64表示 + f := 3.14195 // float64类型，IEEE-754 64位浮点数 + c := 3 + 4i // complex128类型，内部使用两个float64表示 // Var变量可以直接初始化。 var u uint = 7 // unsigned 无符号变量，但是实现依赖int型变量的长度 @@ -99,9 +100,9 @@ can include line breaks.` // 同样是String类型 // 下划线 _ 可以使你“使用”一个变量，但是丢弃它的值。 _,_,_,_,_,_,_,_,_ = s2, g, f, u, pi, n, a3, s4, bs // 输出变量 - fmt.Println(s, c, a4, s3, d2, m) + fmt.Println(s, c, a4, s3, d2, m) - learnFlowControl() // 回到流程控制 + learnFlowControl() // 回到流程控制 } // Go全面支持垃圾回收。Go有指针，但是不支持指针运算。 @@ -117,155 +118,159 @@ func learnMemory() (p, q *int) { } func expensiveComputation() int { - return 1e6 + return 1e6 } func learnFlowControl() { // If需要花括号，括号就免了 - if true { - fmt.Println("told ya") - } - // 用go fmt 命令可以帮你格式化代码，所以不用怕被人吐槽代码风格了，也不用容忍被人的代码风格。 - if false { - // pout - } else { - // gloat - } + if true { + fmt.Println("told ya") + } + // 用go fmt 命令可以帮你格式化代码，所以不用怕被人吐槽代码风格了， + // 也不用容忍被人的代码风格。 + if false { + // pout + } else { + // gloat + } // 如果太多嵌套的if语句，推荐使用switch - x := 1 - switch x { - case 0: - case 1: + x := 1 + switch x { + case 0: + case 1: // 隐式调用break语句，匹配上一个即停止 - case 2: + case 2: // 不会运行 - } + } // 和if一样，for也不用括号 - for x := 0; x < 3; x++ { // ++ 自增 - fmt.Println("iteration", x) - } + for x := 0; x < 3; x++ { // ++ 自增 + fmt.Println("iteration", x) + } // x在这里还是1。为什么？ // for 是go里唯一的循环关键字，不过它有很多变种 - for { // 无限循环 - break // 骗你的 - continue // 不会运行的 - } + for { // 无限循环 + break // 骗你的 + continue // 不会运行的 + } // 和for一样，if中的:=先给y赋值，然后再和x作比较。 - if y := expensiveComputation(); y > x { - x = y - } + if y := expensiveComputation(); y > x { + x = y + } // 闭包函数 - xBig := func() bool { - return x > 100 // x是上面声明的变量引用 - } - fmt.Println("xBig:", xBig()) // true （上面把y赋给x了） - x /= 1e5 // x变成10 - fmt.Println("xBig:", xBig()) // 现在是false + xBig := func() bool { + return x > 100 // x是上面声明的变量引用 + } + fmt.Println("xBig:", xBig()) // true （上面把y赋给x了） + x /= 1e5 // x变成10 + fmt.Println("xBig:", xBig()) // 现在是false // 当你需要goto的时候，你会爱死它的！ - goto love + goto love love: - learnInterfaces() // 好东西来了！ + learnInterfaces() // 好东西来了！ } // 定义Stringer为一个接口类型，有一个方法String type Stringer interface { - String() string + String() string } // 定义pair为一个结构体，有x和y两个int型变量。 type pair struct { - x, y int + x, y int } // 定义pair类型的方法，实现Stringer接口。 func (p pair) String() string { // p被叫做“接收器” // Sprintf是fmt包中的另一个公有函数。 // 用 . 调用p中的元素。 - return fmt.Sprintf("(%d, %d)", p.x, p.y) + return fmt.Sprintf("(%d, %d)", p.x, p.y) } func learnInterfaces() { // 花括号用来定义结构体变量，:=在这里将一个结构体变量赋值给p。 - p := pair{3, 4} - fmt.Println(p.String()) // 调用pair类型p的String方法 - var i Stringer // 声明i为Stringer接口类型 - i = p // 有效！因为p实现了Stringer接口（类似java中的塑型） + p := pair{3, 4} + fmt.Println(p.String()) // 调用pair类型p的String方法 + var i Stringer // 声明i为Stringer接口类型 + i = p // 有效！因为p实现了Stringer接口（类似java中的塑型） // 调用i的String方法，输出和上面一样 - fmt.Println(i.String()) + fmt.Println(i.String()) - // fmt包中的Println函数向对象要它们的string输出，实现了String方法就可以这样使用了。（类似java中的序列化） - fmt.Println(p) // 输出和上面一样，自动调用String函数。 - fmt.Println(i) // 输出和上面一样。 + // fmt包中的Println函数向对象要它们的string输出，实现了String方法就可以这样使用了。 + // （类似java中的序列化） + fmt.Println(p) // 输出和上面一样，自动调用String函数。 + fmt.Println(i) // 输出和上面一样。 - learnErrorHandling() + learnErrorHandling() } func learnErrorHandling() { - // ", ok"用来判断有没有正常工作 - m := map[int]string{3: "three", 4: "four"} - if x, ok := m[1]; !ok { // ok 为false，因为m中没有1 - fmt.Println("no one there") - } else { - fmt.Print(x) // 如果x在map中的话，x就是那个值喽。 - } + // ", ok"用来判断有没有正常工作 + m := map[int]string{3: "three", 4: "four"} + if x, ok := m[1]; !ok { // ok 为false，因为m中没有1 + fmt.Println("no one there") + } else { + fmt.Print(x) // 如果x在map中的话，x就是那个值喽。 + } // 错误可不只是ok，它还可以给出关于问题的更多细节。 - if _, err := strconv.Atoi("non-int"); err != nil { // _ discards value - // 输出"strconv.ParseInt: parsing "non-int": invalid syntax" - fmt.Println(err) - } + if _, err := strconv.Atoi("non-int"); err != nil { // _ discards value + // 输出"strconv.ParseInt: parsing "non-int": invalid syntax" + fmt.Println(err) + } // 待会再说接口吧。同时， - learnConcurrency() + learnConcurrency() } // c是channel类型，一个并发安全的通信对象。 func inc(i int, c chan int) { - c <- i + 1 // <-把右边的发送到左边的channel。 + c <- i + 1 // <-把右边的发送到左边的channel。 } // 我们将用inc函数来并发地增加一些数字。 func learnConcurrency() { // 用make来声明一个slice，make会分配和初始化slice，map和channel。 - c := make(chan int) - // 用go关键字开始三个并发的goroutine，如果机器支持的话，还可能是并行执行。三个都被发送到同一个channel。 - go inc(0, c) // go is a statement that starts a new goroutine. - go inc(10, c) - go inc(-805, c) + c := make(chan int) + // 用go关键字开始三个并发的goroutine，如果机器支持的话，还可能是并行执行。 + // 三个都被发送到同一个channel。 + go inc(0, c) // go is a statement that starts a new goroutine. + go inc(10, c) + go inc(-805, c) // 从channel中独处结果并打印。 // 打印出什么东西是不可预知的。 - fmt.Println(<-c, <-c, <-c) // channel在右边的时候，<-是接收操作。 - - cs := make(chan string) // 操作string的channel - cc := make(chan chan string) // 操作channel的channel - go func() { c <- 84 }() // 开始一个goroutine来发送一个新的数字 - go func() { cs <- "wordy" }() // 发送给cs - // Select类似于switch，但是每个case包括一个channel操作。它随机选择一个准备好通讯的case。 - select { - case i := <-c: // 从channel接收的值可以赋给其他变量 - fmt.Println("it's a", i) - case <-cs: // 或者直接丢弃 - fmt.Println("it's a string") - case <-cc: // 空的，还没作好通讯的准备 - fmt.Println("didn't happen.") - } + fmt.Println(<-c, <-c, <-c) // channel在右边的时候，<-是接收操作。 + + cs := make(chan string) // 操作string的channel + cc := make(chan chan string) // 操作channel的channel + go func() { c <- 84 }() // 开始一个goroutine来发送一个新的数字 + go func() { cs <- "wordy" }() // 发送给cs + // Select类似于switch，但是每个case包括一个channel操作。 + // 它随机选择一个准备好通讯的case。 + select { + case i := <-c: // 从channel接收的值可以赋给其他变量 + fmt.Println("it's a", i) + case <-cs: // 或者直接丢弃 + fmt.Println("it's a string") + case <-cc: // 空的，还没作好通讯的准备 + fmt.Println("didn't happen.") + } // 上面c或者cs的值被取到，其中一个goroutine结束，另外一个保持阻塞。 - learnWebProgramming() // Go很适合web编程，我知道你也想学！ + learnWebProgramming() // Go很适合web编程，我知道你也想学！ } // http包中的一个简单的函数就可以开启web服务器。 func learnWebProgramming() { // ListenAndServe第一个参数指定了监听端口，第二个参数是一个接口，特定是http.Handler。 - err := http.ListenAndServe(":8080", pair{}) - fmt.Println(err) // 不要无视错误。 + err := http.ListenAndServe(":8080", pair{}) + fmt.Println(err) // 不要无视错误。 } // 使pair实现http.Handler接口的ServeHTTP方法。 func (p pair) ServeHTTP(w http.ResponseWriter, r *http.Request) { // 使用http.ResponseWriter返回数据 - w.Write([]byte("You learned Go in Y minutes!")) + w.Write([]byte("You learned Go in Y minutes!")) } ``` |