Programming Language Selec0on. Jonathan Bell November 16, 2010

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1 Programming Language Selec0on Jonathan Bell November 16, 2010

2 Misconcep0ons C is the most efficient programming language Some0mes more inherent to implementa0on Terse code is efficient code Any compiler worth its salt will op0mize down to the terse version Ease of coding is more important than ease of reading Maintenance accounts for 70-90% of cost SoPware development is like heroin: the first hit is free, but then they get you hooked

3 Misconcep0ons SoPware should compile fast Not if it comes at the cost of detec0ng errors Java is the best because it s portable Other languages allow for VM s, in fact, other languages can compile into java byte code

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5 Misconcep0ons SoPware should compile fast Not if it comes at the cost of detec0ng errors Java is the best because it s portable Other languages allow for VM s, in fact, other languages can compile into java byte code Languages should let programmers do what they want Programmers can be dumb and we need to add limits (pointers?)

6 Why focus on language selec0on? Despite what some may argue, there is no universal language Can have long term implica0ons for a product Pick the right tool for the job Correctness? Highly polarized "It is prac0cally impossible to teach good programming to students that have had a prior exposure to BASIC; as poten0al programmers they are mentally mu0lated beyond hope of regenera0on." (Dijkstra)

7 Programming Languages and Correctness Ada on the C130J code had 1/10 th error rate of code wrifen in other languages for the plane*

8 Programming Languages and Correctness Ramp- up 0me Error detec0on Understandability Maintainability Can this all lead to improved sopware?

9 Ramp up 0me Should be able to fully understand the nuance of a language Powerful features are great. Unless you can t use them properly. Languages should seem natural in their construc0on Who knows what this does and hasn t kernel hacked before? #define magic(foo, bar, z) ({ \ const magic( ((bar*)0)->z) * mptr = (foo); \ (bar*)( (char *) mptr - offsetof(bar,z) );})

10 Error Detec0on Loose Typing More flexible C Strong Typing Catch more errors at compile & run 0me Java I/O, system call safety C will not force you to check for error values Java will throw an excep0on Run 0me asser0ons and excep0on handling

11 Understandability Focusing on readability over writeability Dis0nct structural words If(x=y) If(x==y) Read inten0ons as well as instruc0ons

12 Maintainability Standards acceptance Ongoing availability of opera0ons personnel, hardware

13 Programming Languages and Correctness Do these factors contribute to correctness? Get the right tool for the job AND know how to use it Language selec0on can only do so much Perl: print $x unless $x = 0; open(testfile, file ) or die Can t open file: $! ; $_="krjhruaesrltre c a cnp,ohet";$_.=$1,print$2while s/(..)(.)//;

14 Other dimensions for deciding Features/Capabili0es Produc0vity Costs Support structure

15 Other Capabili0es Memory usage Performance Garbage collec0on Integra0on Concurrency Structure

16 Produc0vity LOC per hour? Compila0on overheads IDE availability Refactoring abili0es

17 Costs Compiler IDE Run0me Libraries Hardware Opera0ons staffing

18 Language Features Paradigm Typing Failsafe calls Standardiz ed Garbage Collec0on C C++ Java PHP Lisp Ruby Impera0ve, Procedural Weak/ unsafe Impera0ve, Procedural, OO, generic Strong/ unsafe Impera0ve, OO, reflec0ve, generic Strong/ safe Impera0ve, Procedural, OO, reflec0ve, generic Impera0ve, func0onal, OO, reflec0ve, generic Impera0ve, OO, aspect- oriented, reflec0ve, func0onal Weak/unsafe Strong/Safe Strong/safe No No Yes Yes Yes Yes Yes Yes Yes No Yes (Clisp) No No No Yes Yes Yes Yes

19 Selec0ng a Programming Language What will the system be used for? What plaqorms must it run on? What is your team comfortable with? Create a matrix between candidate languages The values of the matrix may be different for different people!

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21 Selec0ng a Programming Language Don t be stuck in the box Just because you can doesn t mean you should Right tool for the job!

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