Tutorial by Examples: io

Knitr is an R package that allows us to intermingle R code with LaTeX code. One way to achieve this is external code chunks. External code chunks allow us to develop/test R Scripts in an R development environment and then include the results in a report. It is a powerful organizational technique....

The SilverStripe Grid Field Extensions Module has some very nice features to enhance the basic GridField... GridFieldAddExistingSearchButton - a more advanced search form for adding items GridFieldAddNewInlineButton - builds on GridFieldEditableColumns to allow inline creation of records. GridF...

Similar to currying, partial application is used to reduce the number of arguments passed to a function. Unlike currying, the number need not go down by one. Example: This function ... function multiplyThenAdd(a, b, c) { return a * b + c; } ... can be used to create another function that...

Scope guards allow executing statements at certain conditions if the current block is left. import core.stdc.stdlib; void main() { int* p = cast(int*)malloc(int.sizeof); scope(exit) free(p); }

Modules have a one-to-one correspondence with source files. The module name is, by default, the file name with the path and extension stripped off, and can be set explicitly with the module declaration. The ModuleDeclaration sets the name of the module and what package it belongs to. If absent, the...

Assertions are used not to perform testing of input parameters, but to verify that program flow is corect -- i.e., that you can make certain assumptions about your code at a certain point in time. In other words: a test done with Debug.Assert should always assume that the value tested is true. Debu...

You can set a setUp and tearDown function. A setUp function prepares your environment to tests. A tearDown function does a rollback. This is a good option when you can't modify your database and you need to create an object that simulate an object brought of database or need to init a configu...

The Python interpreter compiles code to bytecode before executing it on the Python's virtual machine (see also What is python bytecode?. Here's how to view the bytecode of a Python function import dis def fib(n): if n <= 2: return 1 return fib(n-1) + fib(n-2) # Display the disas...

CPython allows access to the code object for a function object. The __code__object contains the raw bytecode (co_code) of the function as well as other information such as constants and variable names. def fib(n): if n <= 2: return 1 return fib(n-1) + fib(n-2) dir(fib.__code__) de...

Dictionaries map keys to values. car = {} car["wheels"] = 4 car["color"] = "Red" car["model"] = "Corvette" Dictionary values can be accessed by their keys. print "Little " + car["color"] + " " + car["model&q...

Detailed instructions on getting ibm-mobilefirst set up or installed.

To install NLTK with Continuum's anaconda / conda. If you are using Anaconda, most probably nltk would be already downloaded in the root (though you may still need to download various packages manually). Using conda: conda install nltk To upgrade nltk using conda: conda update nltk With a...

There are many compilers that support different versions of the OpenMP specification. OpenMP maintains a list here with the compiler that support it and the supported version. In general, to compile (and link) an application with OpenMP support you need only to add a compile flag and if you use the ...

Given this setup code: var dict = new Dictionary<int, string>() { { 1, "First" }, { 2, "Second" }, { 3, "Third" } }; Use the Remove method to remove a key and its associated value. bool wasRemoved = dict.Remove(2); Executing this code remo...

In Julia, a for loop can contain a comma (,) to specify iterating over multiple dimensions. This acts similarly to nesting a loop within another, but can be more compact. For instance, the below function generates elements of the Cartesian product of two iterables: function cartesian(xs, ys) f...

Julia provides macros to simplify distributing computation across multiple machines or workers. For instance, the following computes the sum of some number of squares, possibly in parallel. function sumofsquares(A) @parallel (+) for i in A i ^ 2 end end Usage: julia> sumo...

Although not traditionally considered loops, the @goto and @label macros can be used for more advanced control flow. One use case is when the failure of one part should lead to the retry of an entire function, often useful in input validation: function getsequence() local a, b @label start ...

The most common conditional in Julia is the if...else expression. For instance, below we implement the Euclidean algorithm for computing the greatest common divisor, using a conditional to handle the base case: mygcd(a, b) = if a == 0 abs(b) else mygcd(b % a, a) end The if...else for...

pushunique!(A, x) = x in A ? A : push!(A, x) The ternary conditional operator is a less wordy if...else expression. The syntax specifically is: [condition] ? [execute if true] : [execute if false] In this example, we add x to the collection A only if x is not already in A. Otherwise, we jus...

shift(x) = ifelse(x > 10, x + 1, x - 1) Usage: julia> shift(10) 9 julia> shift(11) 12 julia> shift(-1) -2 The ifelse function will evaluate both branches, even the one that is not selected. This can be useful either when the branches have side effects that must be evaluat...