Dr. Fred Edison's incredible useful C++14 libraries

May contain traces of industrial strength snake oil.

This is a set of small single-header libraries. They require no installation and only need a C++14 compatible compiler. To use any of them just copy the header file into your own project and include it where needed. If you are using the CMake build system you can also add the full project as a subdirectory and use any of the libraries by linking with the dfelibs target, i.e.

add_subdirectory(<path/to/dfelibs/folder>)
...
target_link_library(<your/project/target> dfelibs)

All libraries are licensed under the terms of the MIT license.

Dispatcher

Register arbitrary functions with the dispatcher

#include <dfe/dfe_dispatcher.hpp>

void func1(int x, double y, std::string z) { ... }
int func2(float a, unsigned int b) { ... }

dfe::Dispatcher dispatch;
dispatch.add("a_function", func1);
dispatch.add("another_function", func2);

and call them by name with regular arguments

dispatch.call("a_function", 12, 0.23, "a message");
dispatch.call("another_function", 3.14f, 23).as<int>();

or with a list of string arguments that are automatically parsed into the correct types

dispatch.call_parsed("a_function", {"12", "0.23", "a message"});

Flat containers

Set-like and map-like containers that store the data internally as sorted, flat arrays continuous in memory (as opposed to a tree-like structure as e.g. in std::set). This simplifies allocations and should yield better performance when only a few elements are stored.

#include <dfe/dfe_flat.hpp>

// set-like
dfe::FlatSet<int> set;
set.insert_or_assign(23);
set.contains(23); // returns true

// map-like
dfe::FlatMap<std::string, std::string> map;
map.emplace("xyz", "something"); // constructs element in-place
map.contains("abc"); // returns false

Namedtuple

Add some self-awareness to a POD type

#include <dfe/dfe_namedtuple.hpp>

struct Record {
  uint32_t x;
  float b;
  int16_t z;
  DFE_NAMEDTUPLE(Record, x, b, z);
}

and write it to disk in multiple formats:

#include <dfe/dfe_io_dsv.hpp>
#include <dfe/dfe_io_numpy.hpp>
#include <dfe/dfe_io_root.hpp> // requires ROOT

dfe::NamedTupleCsvWriter<Record> csv("records.csv"); // or
dfe::NamedTupleTsvWriter<Record> tsv("records.tsv"); // or
dfe::NamedTupleNumpyWriter<Record> npy("records.npy"); // or
dfe::NamedTupleRootWriter<Record> root("records.root", "treename");

csv.append(Record{1, 1.4, -2}); // same call for other writers

The results are either comma-separated text values

x,b,z
1,1.4,-2
...

tab-separated text values

x       b       z
1       1.4     -2
...

binary NPY data or a ROOT TTree. The last option requires the ROOT library as an additional external dependency.

Data stored in one of the delimiter-based formats or as a ROOT tree can also be read back in:

dfe::NamedTupleTsvReader<Record> tsv("records.tsv");
dfe::NamedTupleRootReader<Record> root("records.root", "treename");

Record data;
tsv.read(data); // same call for other readers

Delimiter-based readers support arbitrary column order and extra columns that are not part of the namedtuple definition. They can be read via

Record data;
std::vector<double> extra;
tsv.read(data, extra); // always convert all extra columns to the same type

By default, all elements of the namedtuple must exist for the delimiter-based readers. Some elements can be marked as optional in the reader

dfe::NamedTupleTsvReader<Record> tsv("records.tsv", {"x", "b"});

and the corresponding element in the namedtuple will not be touched if the corresponding column does not exist on file.

Poly

Evaluate polynomial functions and their derivatives using either a (variable-sized) container of coefficients

#include <dfe/dfe_poly.h>

std:vector<double> coeffs = {0.0, 2.0, 3.0, 4.0};
// evaluate f(x) = 2*x + 3*x^2 + 4*x^3 at x=-1.0
double y = dfe::polynomial_val(-1.0, coeffs);
// evaluate df(x)/dx at x=-0.5
double dy = dfe::polynomial_der(-0.5, coeffs);
// evaluate both f(x) and df(x)/dx at x=2.0 at the same time
std::pair<double, double> ydy = dfe::polynomial_valder(2.0, coeffs);

or using the coefficients directly for fixed order polynomials:

// evaluate f(x) = 0.25 + x + 0.75*x^2 at x=0.5
float y = dfe::polynomial_val(0.5f, {0.25f, 1.0f, 0.75f});

Archived libraries

The following libraries are archived and should probably not be used e.g. because they only provide limited functionality or better alternatives exist. But you never know and they might still be useful somewhere.

Histogram

Note: Consider using Boost.Histogram instead.

Compose a multi-dimensional histogram with configurable axis types

#include <dfe/dfe_histogram.hpp>

using H3 =
  dfe::Histogram<float,
    dfe::UniformAxis<float>,
    dfe::OverflowAxis<float>,
    dfe::VariableAxis<float>>;

// axis 0: 16 bins of uniform size, no under/overflow bins
// axis 1: 8 bins of uniform size, additional under/overflow bins
// axis 2: 4 bins of variable size, no under/overflow bins
H3 h({0.0, 1.0, 16}, {-2.0, 2.0, 8}, {1.0, 10.0, 20.0, 30.0, 100.0});

and fill it with weighted or unweighted data

h1.fill(0.5, 0.0, 25);       // weight = 1
h1.fill(0.25, 1.0, 65, 0.3); // weight = 0.3
h1.fill(0.25, 4.0, 65);      // axis 1 overflow
h1.fill(2.25, 1.0, 65);      // fails, due to axis 0 overflow

Small vector

Note: Consider using small_vector from Boost.Container instead.

A vector-like container of elements than can store a fixed number of elements directly in the container without allocating additional memory.

#include <dfe/dfe_smallvector.hpp>

dfe::SmallVector<float, 2> vec;
vec.emplace_back(2.3); // stored directly in the container
vec.emplace_back(4.2); // stored directly in the container
vec.emplace_back(5.0); // memory is allocated and data moved