Reverted style changes, fixed tutorials section and added TOC

Author: Emma Brand

.gitignore

@@ -8,4 +8,6 @@ Thumbs.db
 
 .rbenv-version
 .rmvrc
+*.lock
+
 

Gemfile.lock

@@ -1,6 +1,6 @@
 - page: Home
   url: /
-  
+
 - page: About
   url: /about
 
@@ -10,8 +10,8 @@
 - page: Sponsors
   url: /sponsors
 
-#- page: News
-#  url: /news
+- page: Code
+  url: /tutorial
 
 - page: Contact
-  url: /contact
+  url: /contact

_data/navigation.yml

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+---
+layout: content
+---
+<article class="post">
+  <h1 class="post-title">{{ page.title }}</h1>
+  {{ content }}
+</article>

_layouts/posts.html

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+---
+layout: posts
+title: "Robotics while loop"
+toc: true
+catagotries: [tutorial, code]
+---
+
+# python tutorial 1
+
+The while loop is a convenient way to do the same task over and over again. This
+comes up a lot in robotics, where it is often desirable to let something run in
+a tight loop forever. A good example of this is code which interfaces with an
+instrument. In this case, it is common to write code that simply spends all of
+its time checking the instrument for updates, and then publishing that
+information.
+
+A simple example of this behavior is demonstrated below using the system clock.
+Out of the box, computers are all very good at keeping time, and this code
+shows how to publish that information at a constant rate.
+
+{% highlight python linenos %}
+import time
+
+starttime = time.time()
+
+while True:
+    currenttime = time.time()
+    print("Time is %.02f seconds"%currenttime)
+    time.sleep(0.1)
+
+{% endhighlight %}
+
+This code is an example of an infinite loop. It will run forever doing
+something of questionable importance. To stop the loop, either close the
+terminal running python or push <kbd>CTLR</kbd> + <kbd>c</kbd>.
+
+The time printed to the screen is in seconds since January 1st, 1970. This is
+known as [Unix epoch time](http://en.wikipedia.org/wiki/Unix_time).
+
+There are several things going on in this code, and since this is a tutorial
+they will be broken down line by line.
+
+The first line is an [import](http://docs.python.org/3/reference/import.html)
+statement. Quoting from the first line of the python documentation, "Python
+code in one module gains access to the code in another module by the process
+of importing it." This is a fairly precise definition, but in essence this
+allows code to use the requested module.
+[time](http://docs.python.org/3/library/time.html?highlight=time#module-time)
+is a built in python module, and if python is running this import will
+work. This is not always the case, and sometimes getting imports to work is a
+real challenge :)
+
+The time module has within it a number of functions that relate to computer
+time. The relevant functions are [time](https://docs.python.org/3/library/time.html?highlight=time#time.time)
+and [sleep](https://docs.python.org/3/library/time.html?highlight=time#time.sleep).
+Though a bit weird perhaps, it is not uncommon in python for a word to be
+repeated twice with a period in between, as in line 3.
+
+The [while](https://docs.python.org/3/reference/compound_stmts.html#while)
+loop begins on line 5. A particular characteristic of python appears in
+this statement. Code blocks which can extend for an arbitrary number of lines
+are first ended with the colon character. The code associated with this code
+block (in this case a while loop) is then indicated by *indentation*. All
+statements below the while loop moved one or more tab spaces in from the while
+loop are a part of the while loop.
+
+The [print](https://docs.python.org/3/library/functions.html#print) function
+is how the information moves from inside the program to the computer screen.
+This is a relatively complicated issue in general for robotics, where
+information is moved between many programs frequently. In this example the
+simplest method is used, simply printing the information to the terminal. More
+complicated information transfer is a topic for a later tutorial, but the print
+function is a frequently used first step to understanding a new output.
+
+The print line uses [sting formatting](https://docs.python.org/3/library/stdtypes.html#string-formatting)
+to insert a variable into the printed statement. It is possible to simply print
+the variable by itself as
+
+{% highlight python linenos %}
+print(currenttime)
+{% endhighlight %}
+
+This is often simpler to code, but the output is harder to read. Reviewing the
+documentation the % character is discouraged, but force of habit is hard to break.
+
+
+
+The last line of the while loop is a sleep statement. This is used to free up
+the CPU for 1/10 of a second, a long time to a computer. Like the
+print statement, the sleep statement is a simple approach to a complicated
+topic, in this case [process](https://en.wikipedia.org/wiki/Process_(computing))
+management. This method will be extensively
+used in the robot and covered further in future tutorials. This design decision
+is essentially equivalent to the statement *Nothing needs to be
+addressed within 1/10 of a second*.
+
+---
+
+The second example in this tutorial is a slight extension of the first. The
+template for a mission task has a few distinctions from the instrument reading
+loop show above. In general, these tasks are designed to complete, and good
+practice further ensures that all mission tasks terminate by adding a
+timeout condition.
+
+{% highlight python linenos %}
+import time
+
+isrun = True
+starttime = time.time()
+
+while isrun:
+    currenttime = time.time()
+
+    # mission completion check
+    if False:
+        isrun = False
+
+    # timeout condition
+    if (currenttime - starttime) > 3:
+        break
+
+    print("Time is %.02f seconds"%currenttime)
+    time.sleep(0.1)
+
+print("Goodbye World")
+{% endhighlight %}
+
+The while loop in this example checks a variable before it begins execution. If
+isrun is False, the while loop exits before execution. As written, the while
+loop will never terminate in this way, but it might be fun to try and change
+this behavior.
+
+The timeout behavior takes place on line 14, which checks the current time and
+exits if it has been more than 3 seconds from the start of the loop. The loop
+is then immediately terminated with the break statement. The if loop, and the
+break statement are examples of [flow control](https://docs.python.org/3.7/tutorial/controlflow.html?highlight=break).
+
+The last action of this code is to print the line "Goodbye World". This shows
+how to write code both inside and outside of the while loop.
+
+Well, that is it for now. Hopefully the basic topics covered here will continue
+to be useful into the future.