Tutorial by Examples: a

The system header TargetConditionals.h defines several macros which you can use from C and Objective-C to determine which platform you're using. #import <TargetConditionals.h> // imported automatically with Foundation - (void)doSomethingPlatformSpecific { #if TARGET_OS_IOS // code t...

Abbreviated from https://blogs.dropbox.com/developers/2013/07/using-oauth-2-0-with-the-core-api/: Step 1: Begin authorization Send the user to this web page, with your values filled in: https://www.dropbox.com/oauth2/authorize?client_id=<app key>&response_type=code&redirect_uri=<...

R has several built-in functions that can be used to print or display information, but print and cat are the most basic. As R is an interpreted language, you can try these out directly in the R console: print("Hello World") #[1] "Hello World" cat("Hello World\n") #H...

To have Git ignore certain files across all repositories you can create a global .gitignore with the following command in your terminal or command prompt: $ git config --global core.excludesfile <Path_To_Global_gitignore_file> Git will now use this in addition to each repository's own .git...

A submodule is always checked out at a specific commit SHA1 (the "gitlink", special entry in the index of the parent repo) But one can request to update that submodule to the latest commit of a branch of the submodule remote repo. Rather than going in each submodule, doing a git checkout...

If your latest commit is not published yet (not pushed to an upstream repository) then you can amend your commit. git commit --amend This will put the currently staged changes onto the previous commit. Note: This can also be used to edit an incorrect commit message. It will bring up the default...

The trap is reset for subshells, so the sleep will still act on the SIGINT signal sent by ^C (usually by quitting), but the parent process (i.e. the shell script) won't. #!/bin/sh # Run a command on signal 2 (SIGINT, which is what ^C sends) sigint() { echo "Killed subshell!" } ...

You can use the trap command to "trap" signals; this is the shell equivalent of the signal() or sigaction() call in C and most other programming languages to catch signals. One of the most common uses of trap is to clean up temporary files on both an expected and unexpected exit. Unfortu...

This is an example of dereferencing a NULL pointer, causing undefined behavior. int * pointer = NULL; int value = *pointer; /* Dereferencing happens here */ A NULL pointer is guaranteed by the C standard to compare unequal to any pointer to a valid object, and dereferencing it invokes undefined...

int i = 42; i = i++; /* Assignment changes variable, post-increment as well */ int a = i++ + i--; Code like this often leads to speculations about the "resulting value" of i. Rather than specifying an outcome, however, the C standards specify that evaluating such an expression produc...

int foo(void) { /* do stuff */ /* no return here */ } int main(void) { /* Trying to use the (not) returned value causes UB */ int value = foo(); return 0; } When a function is declared to return a value then it has to do so on every possible code path through it. Undefined beh...

alias word='command' Invoking word will run command. Any arguments supplied to the alias are simply appended to the target of the alias: alias myAlias='some command --with --options' myAlias foo bar baz The shell will then execute: some command --with --options foo bar baz To include mul...

alias -p will list all the current aliases.

The type of the literal Prelude> :t 1 1 :: Num a => a choosing a concrete type with annotations You can specify the type as long as the target type is Num with an annotation: Prelude> 1 :: Int 1 it :: Int Prelude> 1 :: Double 1.0 it :: Double Prelude> 1 :: Word 1 it :: ...

The type of the literal Prelude> :t 1.0 1.0 :: Fractional a => a Choosing a concrete type with annotations You can specify the type with a type annotation. The only requirement is that the type must have a Fractional instance. Prelude> 1.0 :: Double 1.0 it :: Double Prelude> 1....

#include <stdio.h> #include <stdlib.h> #include <string.h> int main(int argc, char **argv) { /* Exit if no second argument is found. */ if (argc != 2) { puts("Argument missing."); return EXIT_FAILURE; } size_t len = str...

Sets are unordered collections of unique values. Unique values must be of the same type. var colors = Set<String>() You can declare a set with values by using the array literal syntax. var favoriteColors: Set<String> = ["Red", "Blue", "Green", "Blu...

println! (and its sibling, print!) provides a convenient mechanism for producing and printing text that contains dynamic data, similar to the printf family of functions found in many other languages. Its first argument is a format string, which dictates how the other arguments should be printed as t...

A simple function that does not accept any parameters and does not return any values: func SayHello() { fmt.Println("Hello!") }

A function can optionally declare a set of parameters: func SayHelloToMe(firstName, lastName string, age int) { fmt.Printf("Hello, %s %s!\n", firstName, lastName) fmt.Printf("You are %d", age) } Notice that the type for firstName is omitted because it is identical ...