CSc 372 - Comparative Programming Languages
1 : Introduction
Christian Collberg
Department of Computer Science
University of Arizona
- In this class we will study three languages:
Prolog, Haskell, and Icon.
- There are several reasons why you would want to learn
a large number of languages:
- There will always be new languages used in
industry. Recently, we've gone from C to Ada
to C++ to Java and (maybe) to C#. Every
computer scientist should be ready to make
this change.
- Learning a new programming paradigm
teaches you new ways to solve problems.
- Functional programming is a way to program in a more
``mathematical'' way.
- An FP program consists of a collection of simple
functions which are combined into more complex
functions, which are combined..., etc.
- FP programs are easier to reason about mathematically
than imperative (C) or object-oriented programs.
- We are going to study Haskell,
one of the more popular modern FP languages.
- Logic programming is a way to program using
ideas from logic, such as first order predicate
calculus.
- There really is only one well-know language in this
class, Prolog, and that is what we
will study.
- Prolog allows you to solve some very complex problems
very easily.
- Icon is a string processing language developed
here at the UofA.
- Icon is really a general purpose imperative language, but it
has some very powerful ways of manipulating strings.
- Other, more modern, languages in this class are
Perl, Python,
Tcl, and Ruby.
- These languages are used more and more in real
applications, since writing a Perl program is often
much faster than writing the equivalent Java/C/C++ program.
A Preview
You Are Not Supposed to Understand This Lecture!!!
yet...
The file hello.pl
![\begin{lstlisting}[language=Prolog]
hello :-
write('Hello World!'),nl.
\end{lstlisting}](img1.gif)
Loading and running
![\begin{lstlisting}[language=csh]
> gprolog
\vert ?- ['hello.pl'].
\vert ?- hello.
Hello World!
\par
yes
\vert ?-
\end{lstlisting}](img2.gif)
The file hello.gh
![\begin{lstlisting}[language=Haskell]
main = putStr (''Hello World'')
\end{lstlisting}](img3.gif)
Loading and running
![\begin{lstlisting}[language=csh]
> hugs
\par
Main> :load hello.gh
Main> main
Hello World
Main>
\end{lstlisting}](img4.gif)
The file hello.icn
![\begin{lstlisting}[language=Pascal]
procedure main()
write(''Hello World!'')
end
\end{lstlisting}](img5.gif)
Compiling and running
![\begin{lstlisting}[language=csh]
> icont hello.icn
> hello
Hello World!
\end{lstlisting}](img6.gif)
![\begin{lstlisting}[language=Java]
class Hello {
String message;
\par
Hello(Stri...
...lo myHello = new Hello(''Hello World'');
myHello.sayit();
}
}
\end{lstlisting}](img7.gif)
The file hello.pl
![\begin{lstlisting}[language=Prolog]
hello2(0).
hello2(N) :-
N>0,
write('Hello World!'),nl,
N1 is N - 1,
hello2(N1).
\end{lstlisting}](img8.gif)
Loading and running
![\begin{lstlisting}[language=Prolog]
> gprolog
\vert ?- ['hello.pl'].
\vert ?- hello2(2).
Hello World!
Hello World!
\end{lstlisting}](img9.gif)
The file hello.gh
![\begin{lstlisting}[language=Haskell]
main n = putStr (unlines (take n (repeat ''Hello World!'')))
\end{lstlisting}](img10.gif)
Loading and running
![\begin{lstlisting}[language=Haskell]
> hugs
\par
Main> :load hello.gh
Main> main 2
Hello World!
Hello World!
\end{lstlisting}](img11.gif)
- repeat "Hello World!" generates an infinite list of
strings.
- take n [...] takes the first n elements of
a list, and throws away the rest.
- unlines [...] concatenates a list of strings into one
string.
The file hello.icn
![\begin{lstlisting}[language=Pascal]
procedure hello(n)
every i:= 1 to n do
write(''Hello World!'')
end
\par
procedure main()
hello(2)
end
\end{lstlisting}](img12.gif)
Compiling and running
![\begin{lstlisting}[language=csh]
> icont hello.icn
> hello
Hello World!
Hello World!
\end{lstlisting}](img13.gif)
Remember...
You Are Not Supposed to Understand This Lecture!!!
yet...
...but you will need to know it all for the final!
- Go to the 372 web page and browse around the information
about the different languages.
- If you own your own computer, download and install the different
compilers/interpreters.
- Try to run the examples in this lecture, on your own machine,
on lectura, or on the Windows machines in the lab.
- In this class we will study three languages: Prolog, Haskell, and Icon.
- Haskell is a functional programming languages.
- Prolog is a logic programming language.
- Icon is a string processing language.
Christian S. Collberg
2005-08-22