Description

A generic collection library for Go.

Dealing with generic containers in Go is not straightforward, due to Go’s type system. Go provides no builtin implementation for common list operations, such as map, reduce and filter. This library aims to provide a generic implementation of these functions for Go programs, without using Go’s reflection mechanism. Type assertions are only necessary in the code using the library.

Currently, a wrapper (Vector) around Go’s builtin slice type is provided as an example implementation of the Collection interface. Your own data structures can be made compatible with the functions presented here by implementing the Collection interface.

Usage

Either implement Collection for your own types or use the Vector implementation provided by this library. The following example shows Map, Reduce and Filter in action, using Vector:

package main

import (
        c "github.com/dhamidi/collection"
        "fmt"
)

func main() {
        incr := func(i c.Value) c.Value {
                return i.(int) + 1
        }
        add := func(a, b c.Value) c.Value {
                return a.(int) + b.(int)
        }
        even := func(a c.Value) bool {
                return a.(int) % 2 == 0
        }

        vector := c.NewVector([]c.Value{1,2,3})
        sumOfEvens := c.Reduce(c.Filter(c.Map(vector,incr), even), add, 0)

        fmt.Printf("Sum: %d\n", c.Reduce(c.Map(vector, incr), add, 0))
        fmt.Printf("Sum of even elements: %d\n", sumOfEvens)
        // Output:
        // Sum: 9
        // Sum of even elements: 6
}

Contributing

Contributions are welcome, as long as your contribution’s code fulfills a few requirements:

1. Write a test for each public function or method.
2. Each public function/method/type has to be documented in way compatible with godoc. See http://blog.golang.org/godoc-documenting-go-code for how to do this.

   Bonus points for providing an Example for the function.

3. Functions that modify the collection passed as an argument should end with `X’ (e.g. `MapX’ for a destructive map function).
4. Type assertions should only be necessary in the program using this library. We can’t and should not determine the correct type of an element.
5. Use GNU style `quotes’ in your documentation.
6. Add two spaces after each sentence. This way everybody can use their favorite editor’s shortcuts for moving by sentences. (( and ) in VIM, M-a and M-e in Emacs).
7. Write code in paragraphs. This makes it possible to use paragraph motion commands to efficiently navigate within a function. Paragraphs should be delimited by the intent of the code. To use an example from the library:

    func NewVector(items []Value) *Vector {
    	data := items
   
    	if items == nil {
    		data = make([]Value, 0)
    	}
   
    	return &Vector{data: data}
    }
       

   The first paragraph describes the function and deals with handling the function’s arguments. The second paragraph deals with the special case of items being nil. The last paragraph is about the value returned by the function.

The rules dealing with `code style’ may seem a little overly pedantic, but ensure that the codebase is consistent and easy to navigate.

Todo

• [ ] break Collection down into smaller interfaces, e.g. (Collection and ImmutableCollection). This way, integrating custom data structures is less effort.
• [ ] supply different collection implementations for Go’s map data structure. Maybe one for representing the keys, one for the values and one for a list of key, value pairs?
• [ ] supply an implementation for the standard library’s container/list.
• [ ] add more functions interacting with the collections, such as take, first, rest, foldr and sort.

License

Copyright (c) Dario Hamidi All rights reserved.

Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer.
2. Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution.
3. Neither the name of the Author nor the names of its contributors may be used to endorse or promote products derived from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS “AS IS” AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

Author

Dario Hamidi <dario.hamidi@gmail.com>, 2013 http://www.github.com/dhamidi/collection