Do Not Fear Recursion

September 11, 2016

There are a lot of algorithms which can be implemented using recursive or iterative style. Actually, everything can be implemented in both styles. For a lot of algorithms, the recursive version is simpler to read, write, and understand. But nevertheless, programmers know, that recursive functions burden a lot of memory consumption, because there is usually a call instruction per recursive call, which puts another call frame on the stack. Interestingly, this is not true sor some special cases.
Read more

Wrapping Algorithms into Iterators

September 4, 2016

Sometimes there is the requirement to generate a range of numbers from some algorithm. Be it a simple range of increasing numbers, or only odd numbers, or only primes, or whatever. Some calculations can be optimized by memorizing some values for the calculation of the next number, just as this applies for fibonacci numbers. This article shows how to wrap such calculations into iterators in order to have performant, and nicely encapsulated algorithms.
Read more

Type List Compile Time Performance

June 25, 2016

Soon, after writing my first meta programs with C++ templates, i realized, that certain programming patterns lead to sky rocketing compile times. I came up with rules of thumb like “Prefer pattern matching over if_else_t”, and “Prefer nested type lists over variadic type lists”. But i did not know how much faster which pattern is, i just knew about tendencies. Finally, i sat down to write some compile time benchmarks, and this blog posts presents the results.
Read more

Generating Integer Sequences at Compile Time

June 24, 2016

In some situations, it can be useful ot generate sequences of numbers at compile time. This article shows how to generate integer sequences with C++ templates, and gives an example how to use it.
Read more

Executing Brainfuck at Compile Time with C++ Templates

June 16, 2016

This article completes a series which aims at explaining how to implement a Brainfuck Interpreter, which runs at compile time, because it is a template meta program.
Read more

Implementing a Turing Tape for Use at Compile Time

May 15, 2016

Turing Machines consist of a tape with memory cells, a tape reader like cassette drives and a program table. Implementing the tape drive part with an array and a pointer is a trivial thing to do with imperative programming languages. It becomes more interesting when learning purely functional programming, especially in the context of template meta programming in C++. As a preparation for the next article, i will show how to implement a turing tape based on type lists, usable at compile time.
Read more

Transformations between User Input/Output and Type Lists

May 14, 2016

Type lists are an important way to represent ordered and unordered sets of types at compile time. These types can be real structure- or class types bundling runtime algorithms etc., but they can also convey actual data at compile time. In order to apply certain compile time processing to data, this data needs to be transformed from and to other representations, which can be provided by the programmer and consumed by run time programs. This article shows how to transform back and forth between strings and character type lists.
Read more

Type Lists

May 8, 2016

Homogenuous data in purely functional programs is typically managed in lists. Items can be appended or prepended to lists, different lists can be concatenated. Lists can be filtered, transformed, mapped, reduced, etc. Having all this nice stuff as a template meta library is quite an enabler for complex compile time meta programs.
Read more

Template Meta Programming Basics

May 5, 2016

C++ template meta programs are at first really hard to read. This is because the template mechanism accidentally became turing complete, although it was invented to enable for type-agnostic programming of generic algorithms. However, now the world knows that the C++ template part of the language is turing complete, people started writing full programs in it, and it enhances the power and flexibility of libraries quite a lot. This article aims to explain some very basic things one needs to know about the C++ template meta programming language, in order to be able to do things with it, or even understand foreign programs.
Read more

Const References to Temporary Objects

March 23, 2016

In both C and C++, it is not a sane idea to hold a reference (or a pointer in C) to a temporarily created object, as the reference is quickly dangling as soon as the assignment is done. But actually, C++ provides an interesting feature, where the life time of a temporary object can be extended to the life time of the reference which points to it.
Read more