Tutorial by Examples: ar

Open and write to a binary file

#include <stdlib.h> #include <stdio.h> int main(void) { result = EXIT_SUCCESS; char file_name[] = "outbut.bin"; char str[] = "This is a binary file example"; FILE * fp = fopen(file_name, "wb"); if (fp == NULL) /* If an erro...

C Language • Files and I/O streams

Allocate and zero-initialize an array with user defined size

#include <stdio.h> #include <stdlib.h> int main (void) { int * pdata; size_t n; printf ("Enter the size of the array: "); fflush(stdout); /* Make sure the prompt gets printed to buffered stdout. */ if (1 != scanf("%zu", &n)) /* If zu is n...

C Language • Arrays

How Indentation is Parsed

Whitespace is handled by the lexical analyzer before being parsed. The lexical analyzer uses a stack to store indentation levels. At the beginning, the stack contains just the value 0, which is the leftmost position. Whenever a nested block begins, the new indentation level is pushed on the stack, ...

Python Language • Indentation

Keyword arguments

Racket functions can also have keyword arguments, which are specified with a keyword followed by the argument expression. A keyword begins with the characters #:, so a keyword argument looks like #:keyword arg-expr. Within a function call this looks like (function #:keyword arg-expr). > (define ...

racket • Functions

Pie Chart

The PieChart class draws data in the form of circle which is divided into slices. Every slice represents a percentage (part) for a particular value. The pie chart data is wrapped in PieChart.Data objects. Each PieChart.Data object has two fields: the name of the pie slice and its corresponding valu...

javafx • Chart

Using external variables

It is possible, inside a closure, to use an external variable with the special keyword use. For instance: <?php $quantity = 1; $calculator = function($number) use($quantity) { return $number + $quantity; }; var_dump($calculator(2)); // Shows "3" You can go further by ...

PHP • Closure

Computing large integer roots

Even though Python natively supports big integers, taking the nth root of very large numbers can fail in Python. x = 2 ** 100 cube = x ** 3 root = cube ** (1.0 / 3) OverflowError: long int too large to convert to float When dealing with such large integers, you will need to use a custom f...

Python Language • Exponentiation

Moving refs around

Running git reset --hard moves refs to the specified hash/ref. Moving MyBranch to b8dc53: $ git checkout MyBranch # moves HEAD to MyBranch $ git reset --hard b8dc53 # makes MyBranch point to b8dc53

Git • Internals

Stripping unwanted leading/trailing characters from a string

Three methods are provided that offer the ability to strip leading and trailing characters from a string: str.strip, str.rstrip and str.lstrip. All three methods have the same signature and all three return a new string object with unwanted characters removed. str.strip([chars]) str.strip acts o...

Python Language • String Methods

Searching a substring with strpos

strpos can be understood as the number of bytes in the haystack before the first occurrence of the needle. var_dump(strpos("haystack", "hay")); // int(0) var_dump(strpos("haystack", "stack")); // int(3) var_dump(strpos("haystack", "stackoverf...

PHP • String Parsing

Compare two files from the web

The following compares two files with diff using process substitution instead of creating temporary files. diff <(curl http://www.example.com/page1) <(curl http://www.example.com/page2)

Bash • Process substitution

Passing parameters to FXML - using a controllerFactory

Problem: Some data needs to be passed to a scene loaded from a fxml. Solution Specify a controller factory that is responsible for creating the controllers. Pass the data to the controller instance created by the factory. FXML <?xml version="1.0" encoding="UTF-8"?> &...

javafx • FXML and Controllers

Type Variables

Type variables are uncapitalized names in type-signatures. Unlike their capitalized counterparts, such as Int and String, they do not represent a single type, but rather, any type. They are used to write generic functions that can operate on any type or types, and are particularly useful for writing...

Elm Language • Types, Type Variables, and Type Constructors

Get started

index.html <!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>Trying out ports</title> </head> <body> <div id="app"></div> <script src="elm.js"></script> ...

Elm Language • Ports (JS interop)

Keyword-only and Keyword-required arguments

Python 3 allows you to define function arguments which can only be assigned by keyword, even without default values. This is done by using star * to consume additional positional parameters without setting the keyword parameters. All arguments after the * are keyword-only (i.e. non-positional) arg...

Python Language • *args and **kwargs

Convert all columns of a data.frame to character class

A common task is to convert all columns of a data.frame to character class for ease of manipulation, such as in the cases of sending data.frames to a RDBMS or merging data.frames containing factors where levels may differ between input data.frames. The best time to do this is when the data is read ...

R Language • Data frames

Setting parameters for PreparedStatement

Placeholders in the query string need to be set by using the set* methods: String sql = "SELECT * FROM EMP WHERE JOB = ? AND SAL > ?"; //Create statement to make your operations PreparedStatement statement = connection.prepareStatement(sql); statement.setString(1, "MANAGER&...

jdbc • PreparedStatement

char literals

char literals are defined by wrapping the value with single-quotes ': char c = 'h'; Character literals may contain escape sequences. See String Escape Sequences A character literal must be exactly one character long (after all escape sequences have been evaluated). Empty character literals are ...

C# Language • Literals

Conversion to and from Arrays

Hashes can be freely converted to and from arrays. Converting a hash of key/value pairs into an array will produce an array containing nested arrays for pair: { :a => 1, :b => 2 }.to_a # => [[:a, 1], [:b, 2]] In the opposite direction a Hash can be created from an array of the same form...

Ruby Language • Hashes

git-tfs clone from bare git repository

Cloning from a git repository is ten times faster than cloning directly from TFVS and works well in a team environment. At least one team member will have to create the bare git repository by doing the regular git-tfs clone first. Then the new repository can be bootstrapped to work with TFVS. $ git...

Git • git-tfs