Overview

ezSlice is a class to parse array slice strings like those used in Python or MATLAB. Examples are in the unit test test_ezSlice.cpp.

This is a templated, self-contained, single header implementation C++ class for parsing array slice operator strings that specify a min, max, and stride, such as "1:10:2", "::3" or "-1,-5,-2". There is an option to use any offset based indexing desired, such as 0-based for C/Python arrays, or 1-based for Fortran/MATLAB indexing. Reverse indexing is allowed, as well as relative to an array end. This class won't do the actual slice/sampling of an array; instead it only parses a string and returns the index limits and stride, or an STL vector of indices if desired.

Features

• Single C++ header implementation.
• Only depends on STL.
• Uses template for slice index type, so you can choose what's best for you: int, size_t, unsigned int, char, etc.
• Custom delimiter instead of common ":" or ",".
• Optional min, max, stride slice parameters. Some examples: "..." denotes entire index range. "2::3" will start with second (or third) index and skip by 3. "::-1" denotes entire range but in reverse. "-1" is the last element. "-5:" is from fifth from last until end.

Download

Source code

Git

C++ Usage

// Some excerpts from test/test_ezSlice.cpp.
#include "ezSlice.hpp"

int main() {
  ez::ezSlice<int> slice;
  int min, max, stride, n = 10;
  std::vector<int> values;

  // Set min,max,stride without a delimiter.
  slice.set("2",0,0);
  slice.get(min,max,stride,n);
  slice.get(values,n); // Returns [ 2 3 4 5 6 7 8 9 ]

  slice.set("2","7","2");
  slice.get(min,max,stride,n);
  slice.get(values,n); // Returns [ 2 4 6 ]

  // Set a string to parse.
  std::string str = "2:5";
  slice.set(str,':');
  slice.get(min,max,stride,n);
  slice.get(values,n); // Returns [ 2 3 4 5 ]

  // Reverse stride.
  str = "::-3";
  slice.set(str,':');
  slice.get(min,max,stride,n);
  slice.get(values,n); // Returns [ 9 6 3 0 ]

  // Get all along dimension.
  // ":" and "::" will return same result in this context.
  str = "..."; 
  slice.set(str,':');
  slice.get(min,max,stride,n);
  slice.get(values,n); // Returns [ 0 1 2 3 4 5 6 7 8 9 ]

  // Of cource single value works too, but use an offset.
  str = "3";
  slice.set(str,':', -1);
  slice.get(min,max,stride,n);
  slice.get(values,n); // Returns [ 2 ]

  // Without offset, we get different result.
  slice.set(str,':');
  slice.get(min,max,stride,n);
  slice.get(values,n); // Returns [ 3 ]

  return 0;
}

Installation

make test
make memtest
make clean
sudo make install PREFIX=/usr/local

Distribution

make html
make clean
make dist VER=0.1.1

Publishing

ssh -t rsz,ezslice@shell.sourceforge.net create
scp html/* rsz,ezslice@shell.sourceforge.net:/home/project-web/ezslice/htdocs
scp ../ezSlice-0.1.1.tar.gz rsz,ezslice@shell.sourceforge.net:/home/frs/project/e/ez/ezslice

License

Copyright 2011, 2012 Remik Ziemlinski (see LICENSE.MIT)