Tutorial by Examples: co

Compiling your Program for Profiling

The GHC compiler has mature support for compiling with profiling annotations. Using the -prof and -fprof-auto flags when compiling will add support to your binary for profiling flags for use at runtime. Suppose we have this program: main = print (fib 30) fib n = if n < 2 then 1 else fib (n-1)...

Haskell Language • Optimization

Cost Centers

Cost centers are annotations on a Haskell program which can be added automatically by the GHC compiler -- using -fprot-auto -- or by a programmer using {-# SCC "name" #-} <expression>, where "name" is any name you wish and <expression> is any valid Haskell expression:...

Haskell Language • Optimization

Compound assignment operators

SQL Server 2008 R2 Supported compound operators: += Add and assign -= Subtract and assign *= Multiply and assign /= Divide and assign %= Modulo and assign &= Bitwise AND and assign ^= Bitwise XOR and assign |= Bitwise OR and assign Example usage: DECLARE @test INT = 42; SET @test...

Microsoft SQL Server • Variables

Place allocation and cleanup code next to each other

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); }

D Language • Scope guards

Multiple, nested scopes

import std.stdio; void main() { writeln("<html>"); scope(exit) writeln("</html>"); { writeln("\t<head>"); scope(exit) writeln("\t</head>"); "\t\t<title>%s</title>".write...

D Language • Scope guards

Using move semantics on containers

You can move a container instead of copying it: void print(const std::vector<int>& vec) { for (auto&& val : vec) { std::cout << val << ", "; } std::cout << std::endl; } int main() { // initialize vec1 with 1, 2, 3, 4 and...

C++ • Move Semantics

Insert data using COPY

COPY is PostgreSQL's bulk-insert mechanism. It's a convenient way to transfer data between files and tables, but it's also far faster than INSERT when adding more than a few thousand rows at a time. Let's begin by creating sample data file. cat > samplet_data.csv 1,Yogesh 2,Raunak 3,Varun ...

postgresql • INSERT

Indent code properly

Proper indentation gives not only the aesthetic look but also increases the readability of the code. For example, consider the following code: %no need to understand the code, just give it a look n = 2; bf = false; while n>1 for ii = 1:n for jj = 1:n if ii+jj>30 bf = true; break end...

MATLAB Language • MATLAB Best Practices

stroke (a path command)

context.stroke() Causes the perimeter of the Path to be stroked according to the current context.strokeStyle and the stroked Path is visually drawn onto the canvas. Prior to executing context.stroke (or context.fill) the Path exists in memory and is not yet visually drawn on the canvas. The unu...

html5-canvas • Path (Syntax only)

fill (a path command)

context.fill() Causes the inside of the Path to be filled according to the current context.fillStyle and the filled Path is visually drawn onto the canvas. Prior to executing context.fill (or context.stroke) the Path exists in memory and is not yet visually drawn on the canvas. Example code usi...

html5-canvas • Path (Syntax only)

clip (a path command)

context.clip Limits any future drawings to display only inside the current Path. Example: Clip this image into a triangular Path <!doctype html> <html> <head> <style> body{ background-color:white; } #canvas{border:1px solid red; } </style> <sc...

html5-canvas • Path (Syntax only)

Display the bytecode of a function

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...

Python Language • Accessing Python source code and bytecode

Exploring the code object of a function

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...

Python Language • Accessing Python source code and bytecode

NLTK installation with Conda.

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...

nltk • Getting started with nltk

Compilation

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 ...

openmp • Getting started with openmp

Collatz sequence

The while loop runs its body as long as the condition holds. For instance, the following code computes and prints the Collatz sequence from a given number: function collatz(n) while n ≠ 1 println(n) n = iseven(n) ? n ÷ 2 : 3n + 1 end println("1... and 4, 2, 1, ...

Julia Language • while Loops

Ternary conditional operator

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...

Julia Language • Conditionals

Simple Producer/Consumer

Overview Create a queue that we can send a message to. Oracle will notify our stored procedure that a message has been enqueued and should be worked. We'll also add some subprograms we can use in an emergency to stop messages from being deqeued, allow dequeuing again, and run a simple batch job t...

Oracle Database • Oracle Advanced Queuing (AQ)

Accessing form controls from other threads

If you want to change an attribute of a control such as a textbox or label from another thread than the GUI thread that created the control, you will have to invoke it or else you might get an error message stating: "Cross-thread operation not valid: Control 'control_name' accessed from a th...

.NET Framework • Threading

Rules of Automatic Semicolon Insertion

There are three basic rules of semicolon insertion: When, as the program is parsed from left to right, a token (called the offending token) is encountered that is not allowed by any production of the grammar, then a semicolon is automatically inserted before the offending token if one or more o...

JavaScript • Automatic Semicolon Insertion - ASI