Archives
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ASP Classic Compiler is now open source
After weeks of preparation, I have opened the source code for my ASP Classic Compiler under the Apache 2.0 license. I conceived the project in 2009 when I joint a company that had a large amount of ASP Classic code. The economy was very slow at the time so I had some energy left to start the work as a hobby. As the economy recovers, I was getting busier with my day-time job. We converted most of our ASP Classic code to .net so that this project would no longer be useful for my own use. However, I truly hope that this project will be useful to those who can still use it.
The project had gone a long way to implement most features in the VBScript 3.0 standard. It is capable of running the Microsoft FMStock 1.0 end to end sample application. I chose VBScript 3.0 in my initial implementation because VBScript 3.0 is a language with dynamic type and static membership. ASP Classic Compiler is faster than most of the Javascript implementations and is about 3 times faster than the IIS ASP interpreter in limited benchmark test. Many users have requested VBScript 5.0 features such as Class, Execute and Eval. VBScript 5.0 has dynamic membership like Javascript. To avoid the performance hit, I have done some research to optimize the performance for the mostly static scenariou, but have yet to find time to implement it.
For this project to be successful, I truly need community involvement. In the next few days, I will outline what need to be done. I will stay as the project lead until we find a suitable new leader.
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New VB.NET Syntax since VS2005
I have not used VB.NET seriously after VS2003. Recently, I had to maintain an old VB.NET application so I had to spend a bit time to find out the VB equivalent of new C# syntax introduced in VS2005 or later:
Category C# VB.NET Generics List<string> List(Of String) Object Initializer new Person() { First=”a”, Last=”b” } New Person() With {.First = “a”, .Last = “b” } Anonymous Type var a = new { First=”a”, Last=”b” }; Dim a= New With {.First = “a”, .Last = “b” } Array or Collection Initializer int[] a = {0, 2, 4, 6, 8};
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int[] a = new int[] {0, 2, 4, 6, 8};Dim a() as Integer = {0, 2, 4, 6, 8}
or
Dim a() as Integer = New Integer() {0, 2, 4, 6, 8}Dictionary Initializer Dictionary<int, string> d = {{1, "One"}, {2, "Two"}}; Dim d As Dictionary(Of Integer, String) = {{1, "One"}, {2, "Two"}} Lambda Expression x => x * x function(x) x*x Multiline Lambda Expression (input parameters) => {statements;} function(input parameters)
statements
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Relating software refactoring to algebra factoring
Refactoring is a fairly common word in software development. Most people in the software industry have some ideas of it. However, it was not clear to me where the term comes from and how it relates to the factor we learnt in algebra. A Bing search indicates that the word Refactoring origin from Opdyke’s Ph.D. thesis used for restructuring in object oriented software, but is not clear how it relates to the factor we normally know. So I attempt to make some sense out of it after the fact.
In algebra, we know a factor is part that participated in a multiplication. For example, if C = A * B, we call A and B factors of C.
Factors are often used to simplify computation. Taking the reverse distribution identity of multiplication as an example, C * A + C * B can be rewritten as C * (A + B). This will improve computational efficiency if multiplication is far more expensive than addition. C in this case is called the common factor in the two terms, C * A and C * B. If there are no common factors between A and B, we call C the greatest common factor (GCF) the two terms.
To identify the GCF of two numbers, we usually find all the prime factors of numbers and include the greatest common count of those prime factors. For example, if we want to find the GCF of 72 and 120, we would like 72 as 23 * 32 and 120 as 23 * 31 * 51. Then the GCF would be 23 * 31 = 24. (Note that in real computer program we usually calculate GCF using Euclid’s algorithm).
Now let us see an example of analogy to algebra factoring in Boolean algebra. There is an identity (A and B) or (A and C) = A and (B or C). If we relate “and” to * and “or” to +, the above identity would be very similar to distribution identity in algebra.
In software refactoring, we usually identify the longest common sequence that is duplicated (let me set parameterization aside for simplicity) and try to reuse the sequence as a single unit. How do we find an analogy to algebra? Let us consider an instruction in a sequence as a function that take the state of computer as input and return the modified state. Then a sequence of instructions can be written as f1(f2(f3(…fn()))). If we replace the () symbol with *. Then we can write above as f1 * f2 * f3 * … * fn. Now we use + to denote any situation that we need branching. For example, we could write if (cond) { A } then { B } as A + B. Now let use apply this notation to a more complex example:
if (cond) { A; B; C; } else { D; B; E; }A to E above are block of code. So using the above notation, we can rewrite it as A * B * C + D * B * E. Now if we try to factor this expression, we get (A + D) * B * (C + E) (Note that this is a bit different to normal Algebra factoring). Now we expand the above expression into code, we would get something like:
if (cond) { A; } else { D; } B; if (cond) { C; } else { E; }That is in fact one of fairly common types of refactoring.
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Teaching high school kids ASP.NET programming
During the 2011 Microsoft MVP Global Summit, I have been talking to people about teaching kids ASP.NET programming. I want to work with volunteer organizations to provide kids volunteer opportunities while learning technical skills that can be applied elsewhere. The goal is to teach motivated kids enough skill to be productive with no more than 6 hours of instruction. Based on my prior teaching experience of college extension courses and involvement with high school math and science competitions, I think this is quite doable with classic ASP but a challenge with ASP.NET. I don’t want to use ASP because it does not provide a good path into the future. After some considerations, I think this is possible with ASP.NET and here are my thoughts:
· Create a framework within ASP.NET for kids programming.
· Use existing editor. No extra compiler and intelligence work needed.
· Using a subset of C# like a scripting language. Teaches data type, expression, statements, if/for/while/switch blocks and functions. Use existing classes but no class creation and OOP.
· Linear rendering model. No complicated life cycle.
· Bare-metal html with some MVC style helpers for widget creation; ASP.NET control is optional. I want to teach kids to understand something and avoid black boxes as much as possible.
· Use SQL for CRUD with a helper class. Again, I want to teach understanding rather than black boxes.
· Provide a template to encourage clean separation of concern.
· Provide a conversion utility to convert the code that uses template to ASP.NET MVC. This will allow kids with AP Computer Science knowledge to step up to ASP.NET MVC.
Let me know if you have thoughts or can help.