Assignment 1 - Nick Carter

Nick_Carter.cfdg

@@ -0,0 +1,50 @@
+// Nick Carter
+// DSLs Fall 2014
+// Extensively referenced documentation on contextfreeart.org
+// Inspiration for tree design in context-free from 
+// http://www.contextfreeart.org/phpbb/viewtopic.php?t=581
+
+
+startshape WORLD
+
+background {b -1} 
+
+rule WORLD {
+
+     SUN {size 10 x 15 y 50} 
+	// forest
+	100* {s 0.9 x -4 y 4 h 10} ROW {h 114.86 sat 1.0000 b 1.0000}
+}
+
+rule ROW {
+	100* {s 0.9 x 4 y 4 b -.1} SEED {}
+}
+
+// tree
+rule SEED {BRANCH {}}
+
+rule BRANCH {
+	LINE {y 0 r 0}
+	FORK {y 6 size 0.7}
+}
+
+rule FORK {
+     BRANCH {size 0.7 y 0.1 rotate 30}
+     BRANCH {size 0.7 y 0.1 rotate -30}
+}
+
+rule LINE {
+	TRIANGLE [ s 1 20 y 0.26 ]
+}
+
+rule SUN {
+    TRIANGLE [ r  30 x 0.5 s 1 0.5 h 7.21 sat 0.9744 b 1.0000]
+    TRIANGLE [ r  90 x 0.5 s 1 0.5 h 36.87 sat 1.0000 b 1.0000]
+    TRIANGLE [ r 150 x 0.5 s 1 0.5 h 7.21 sat 0.9744 b 1.0000]
+    TRIANGLE [ r 210 x 0.5 s 1 0.5 h 36.87 sat 1.0000 b 1.0000]
+    TRIANGLE [ r 270 x 0.5 s 1 0.5 h 7.21 sat 0.9744 b 1.0000]
+    TRIANGLE [ r 330 x 0.5 s 1 0.5 h 36.87 sat 1.0000 b 1.0000]
+
+    CIRCLE [ s 0.75  b 1 h 60.60 sat 0.9055 b 1.0000]
+}
+

context-free.md

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 # Context Free
 
 ##  Who is this programming language for?
+This programming language seems like it is mostly targeted at people who need to create graphics in a very structured way.
+Those that just want to draw or paint may be better served by a digital tablet. However, I think there is a use case for needing a 
+highly rigid, editable description for what you are creating. Perhaps art for boxes or items that could change size could 
+make good use of this type of quickly editable description.
 
 
 ## What is easy to do in this language? Why is it easy?
+It is easy to adapt elements and to reuse ideas. The concept of rules makes it very easy to take one idea and use 
+it a lot of times. It is also very easy to take an element and change it in a subtle way and see how the change 
+affects the outcome. These are easy because of the encapsulation of shape parts into separate function like elements.
+These can then be used together to compose the full image. 
 
 
 ## What is hard to do in this language? Why is it hard?
+It is hard to build complicated computations. Multi dimensional loops are possible, but it is hard to do operations much more complicated
+than addition and subtraction. I created some trees in my program, but when I looked into more complicated fractals it didn't seem
+feasible. It seems like they have purposely restricted the function set away from more mathematical ideas to preserve simplicity and ease of use. 
 
 
 ## How did you learn how to program in this language?
+I looked at sample programs and code in the documentation, the `welcome` program, and some
+forum posts that discussed tricks in the language.
 
 
 ## What is the underlying _computational model_ for this programming language? 
 _We don't yet have a great definition of the term "computational model". 
 For now, try to come up with the clearest, most concise explanation of what 
 happens when a ContextFree program runs._
 
+A ContextFree program seems very declarative. By this I mean that it seems like programs in context free are executed as
+following a tree of rules. The program begins at the root `startshape` and follows all possible rule paths until there are 
+no more paths available or the paths get to small to be rendered reasonably (so recursive operations end when the recursion gets down
+to the sub-pixel level).
+
 
 ## What do you think is interesting about the ContextFree program you wrote?
+I really liked exploring the gradient abilities in ContextFree. I used a multi-dimensional 
+loop to create a forest that changed hue along one axis and changed brightness along the 
+second axis. I set the size such that the viewer is left with the impression that the 
+forest might extend to infinity. 
 

my-dsl.md

@@ -2,37 +2,74 @@
 _What is the name of the language? Link the name to its webpage 
 (if appropriate)._
 
+The language is called `crontab`. [crontab.org](http://crontab.org/)
+
 
 # Domain
 _Describe the language's domain in five words._
 
+Expressing when to execute commands.
+
 
 # Computational model
 _What is the underlying computational model of this language? To answer this 
 question, provide a high-level description (no more than 100 words) of the 
 computation that occurs when someone executes a program in this language._
 
+When someone executes a crontab program, the program parses each line from first to last. Each line 
+is an expression that translates to a encoded time interval (anywhere from every few years to every minute) 
+and a command. The time encoding specifies when and with what frequency the command should be executed. 
+The program then runs the command each time the specified interval elapses. So, the computational model 
+likely looks like a priority queue in which as each task's time comes up, it is executed and put back in 
+the queue for its next time.
+
 
 # DSL-ness
 _Fowler writes about a spectrum of languages, from general-purpose languages to 
 "purely" domain-specific. Where does the DSL you chose fall on this spectrum, 
 and why?_ 
 
+I believe this language is very close to the "purely" domain specific side.
+In this language, it is only possible to express when to do commands. The commands are written in a different language (bash). So, the
+expressiveness of crontab is limited to when and what. There is no general purpose loop or conditionals built into the language, although 
+there is an ability to create variables. 
+It is a language that feels like a programming language with the "terseness" that Fowler seems to like. The syntax is extremely light 
+weight -- a given statement has a interval 
+specification and a command.
+
 
 # Internal or external?
 _Is the language implemented as an internal or external DSL? 
 Justify your answer._
 
+This is an external DSL. It has its own syntax that is not very similar to other languages.
+Although it makes use of other languages in its execution, those languages are not part of the DSL.
+
 
 # Host language
 _What language(s) was (were) used to implement the DSL?_
 
+The cron utility, the main (and perhaps only) user of the crontab syntax, is implemented in `c`.
 
 # Benefits
 _Identify one potential benefit of the DSL: how is a programmer's life or a 
 company's bottom line made easier by the existence of this language?_
 
+This DSL makes it very easy to specify a task that needs to occur in a repeated manner. 
+Instead of having to write a program
+that has some form of daemon that runs continuously, 
+waiting for a given interval to elapse 
+before running a command, this DSL can be used to accomplish the same thing using a
+pre-written architecture.
+
 
 # Drawbacks
 _Identify one potential drawback of the DSL: what does a programmer or company 
 lose by using this DSL instead of a general-purpose language?_
+
+A general-purpose language is still necessary to make use of this language. It is not
+possible to specify what, exactly, to do at a given time without making use of another language. 
+However, this is less of a drawback than an indicator that this is a very specific language. 
+One more definitive drawback in the domain of scheduling events is that this DSL lacks an ability to specify triggers for
+an event outside of time intervals. There is no
+manner in which to specify that an action should occur when another event occurs.