foges/ftl

C++ functional tools library

The goal of this minimal library is to promote functional concepts in C++.

Summary

This library is based around a sequence class, generators, and the let keyword.

class seq -- creates a lazy immutable sequence from a generator, and defines methods such as map, filter, reduce, sorted, split, take_while, etc.. By lazy we mean that elements are only evaluated as needed, or when the eval() method is explicitly called.
Generators -- construct a seq to generate a sequence of values, examples include range, iota, unfold.
#define let const auto -- C++ treats variables as mutable by default, and as programmers we have a tendancy to stick to defaults. Behavior can be hard to get around, especially if you don't give people an incentive to change. By defining let == const auto, we give C++ programmers an easier way to define variables, while at the same time encouraging immutability. In addition, by decreasing the focus on explicitly writing the type name, there is more space to focus on writing readable variable names. That being said, we understand that not everyone likes immutability (or more probably preprocessor hash-defines) forced on them. If you're one of these people you can simply comment it out one line in include/ftl/flt.h. Don't worry, the library itself does not use the let keyword, so you won't break anything (apart from tests) by commenting out this line.

Other classes of interestes are:

class memoize -- memoize a function call.

Examples

Take a look at the examples folder for some great ways to use ftl. Here are a couple of example:

#include <assert.h>
#include <vector>

#include <ftl/ftl.h>

void map_filter_reduce() {
  let a = std::vector<int>{1, 2, 3};
  let res = ftl::make_seq(a.begin(), a.end())
      .map([](let x){ return x * x; })
      .filter([](let x){ return x > 1; })
      .reduce(0, [](let acc, let x) { return acc + x; });
  assert(res == 13);
}

void line_count() {
  std::ifstream f("text.txt");
  let num_lines = ftl::read(f).count();
}

Usage

This is a header only library. Simply add #include <ftl/ftl.h> to your file.

If you'd like syntax highlighting for let in vim, just add the keyword to your c.vim syntax file. Find the line syn keyword cStorageClass and add it.

Tests

To run the tests please install gtest and then run

mkdir -p build && cd build
cmake -DCMAKE_BUILD_TYPE=Release -DGTEST_PATH=<your-gtest-path> ..
make -j
./test_ftl

Todo

file to seq
investigate parallelism

foges / ftl