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The semigroup, or how a bunch of math snuck into my program

This is a story about an idea, an abstraction if you will. As software developers we deal in abstractions constantly, but I want to talk to you about one particular idea, the idea of +. Addition is pretty fundamental as a concept, so let's run through the basics. You'll be familiar with some common forms of addition like integer addition 1 + 2 = 3 and rational addition 1/2 + 2/3 = 7/6. But what does it mean to be able to add something? Could we add functions? What about optional values?

One answer to that question is provided by algebra a lot of algebra is spent defining sets of things and what operations can be performed on them. And what algebra will tell us is that the things we tend to think of as being addable are generally called Semigroups. A Semigroup is a set where all items in the set can be added together so that for every a, b, and c in the set (a + b) + c = a + (b + c). I

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find . -type f | xargs du -h | sort -h

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As software developers we use datastructures all the time Linked Lists, Hash Maps, Stacks. Most datastructures have a set of related operations that we can think of as the core pieces that define that structure in Scala we call the collection of those operations a Trait on in Java an Interface. A Hash Map exposes the Map interface and has an operations to add a key and value +, remove a key -, retrieve the value at key get and an operation like fold to operate over the List of keys and values.

We have certain expectations of these datastructures from our experiences, we expect Maps to be hash maps, and we expect queues to be stacks. But there's no law that requires that. A common replacement of as Hash Map is a Tuple List,

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DBus failure! This is most likely caused by the wicd daemon stopping while wicd-curses is running. Please restart the daemon, and then restart wicd-curses.
Traceback (most recent call last):
  File "/usr/share/wicd/curses/wicd-curses.py", line 921, in call_update_ui
    self.update_ui(True)                                
  File "/usr/share/wicd/curses/wicd-curses.py", line 88, in wrapper
    return func(*args, **kargs)
  File "/usr/share/wicd/curses/wicd-curses.py", line 932, in update_ui
    self.handle_keys(input_data[1])
  File "/usr/share/wicd/curses/wicd-curses.py", line 913, in handle_keys
    self.diag.save_settings()

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DBus failure! This is most likely caused by the wicd daemon stopping while wicd-curses is running. Please restart the daemon, and then restart wicd-curses.
Traceback (most recent call last):
  File "/usr/share/wicd/curses/wicd-curses.py", line 921, in call_update_ui
    self.update_ui(True)                                
  File "/usr/share/wicd/curses/wicd-curses.py", line 88, in wrapper
    return func(*args, **kargs)
  File "/usr/share/wicd/curses/wicd-curses.py", line 932, in update_ui
    self.handle_keys(input_data[1])
  File "/usr/share/wicd/curses/wicd-curses.py", line 913, in handle_keys
    self.diag.save_settings()

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Traceback (most recent call last):
  File "/usr/lib/pymodules/python2.7/django/core/handlers/base.py", line 101, in get_response
    request.path_info)
  File "/usr/lib/pymodules/python2.7/django/core/urlresolvers.py", line 252, in resolve
    sub_match = pattern.resolve(new_path)
  File "/usr/lib/pymodules/python2.7/django/core/urlresolvers.py", line 158, in resolve
    return ResolverMatch(self.callback, args, kwargs, self.name)
  File "/usr/lib/pymodules/python2.7/django/core/urlresolvers.py", line 164, in _get_callback
    self._callback = get_callable(self._callback_str)
  File "/usr/lib/pymodules/python2.7/django/utils/functional.py", line 124, in wrapper

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fake = require("fake")

var namespace = { x: function () { this.whatever = "skimpy" } }

fakeX = fake.create()
fakeX.expects(namespace, "X")
     .andReturns("AASDFASDF")

var y = new namespace.X()
assert.equal(y, "AASDFASDF")

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package com.conbere.anders.escape;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.view.SurfaceView;
import android.view.SurfaceHolder;

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  public EscapeView(Context context, AttributeSet attrs) {
    super(context, attrs);
    this.context = context;
    SurfaceHolder holder = getHolder();
    holder.addCallback(this);
    this.thread = new EscapeThread(holder, context);
  }

  @Override
  public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {

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  class EscapeThread extends Thread {
    public SurfaceHolder surfaceHolder;
    public Context context;
    private boolean running;

    public EscapeThread(SurfaceHolder holder, Context cont) {
      this.surfaceHolder = holder;
      this.context = cont;
      this.running = false;
    }