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ITEC 380

Explore the fundamentals of functional programming in Lecture 6 of our series. This session covers key concepts including lambda expressions, loops, and the principle of laziness. We delve into the structures and classes that are vital in programming languages, with a focus on Lisp. Participants will engage in debugging exercises and learn how to interface with external systems. Essential homework, review sessions, and exam preparation for next week’s midterm will also be discussed. Enhance your understanding of variable scopes and functions in Lisp.

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ITEC 380

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  1. ITEC 380 Organization of programming languages Lecture 6 – Functional Programming

  2. Review • Lambda • Loops • Lazyness + Macros • Structures / classes • Homework • Questions?

  3. Book link • http://mitpress.mit.edu/sicp/full-text/book/book.html • More about basics of languages • Optional for study

  4. Objectives • Review basics of LISP • Debugging / Lower level implementation • Interfacing with the outside world • General discussion of wrapping • Exam next week (midterm)

  5. Global Variables • Not good practice, but an example of variables in Lisp • Example (defparameter*tiny* 1) (defparameter*large* 10) *tiny* *large* Note: * Is just a stylistic convention

  6. FunctionsOperations • Create a function accomplish a task • Example • Note: Functions return their information by default (no need for return value) (defparameter *small* 1) (defparameter *big* 10) (defunaddtwo () (* (- *big* *small*) 2 ) )

  7. Local variables • Specify the scope of a problem (defunlocalTest() (let ((a 5) (b 6)) (c(+ a b)) ) )

  8. Conditionals • Simple to use • (if (conditional) (then) (else) ) • Sometimes you will make a function call instead of the ‘(list data) • Also have when and unless (if (> 5 3) (princ "Larger") (princ "Smaller") )

  9. Data • Numbers • 4/6 => How would this be put into lisp? • 4.0/6 => Ditto? • Strings • Enclose in “ “ otherwise will be treated like a function • Items as a list • ‘(+ 2 1) versus (+ 2 1)

  10. Working with lists • Three basic functions • cons • Combine lists together • car • Access the first item in a list • cdr • Return the second element to the end of a list

  11. In-class coding • Problems • Given a list of items as a parameter to your function, return true if there are any duplicates, nil other wise

  12. Lisp beyond the shell • OpenGL - Common graphical language • C based, how do we write Lisp w/ it? • Example • https://github.com/3b/cl-opengl/blob/master/examples/mesademos/gears-raw.lisp#L17

  13. Bindings • Many different approaches we will look at 2 • CFFI • Common Foreign Function Interface • I.e. how to interface with the outside world • Situation • Have X project you want to use in your code • You speak Greek they speak French…

  14. Example • From Common-lisp.net (asdf:oos 'asdf:load-op :cffi) ;;; Nothing special about the "CFFI-USER" package. We're just ;;; using it as a substitute for your own CL package. (defpackage :cffi-user (:use :common-lisp :cffi)) (in-package :cffi-user) (define-foreign-librarylibcurl (:unix (:or "libcurl.so.3" "libcurl.so")) (t (:default "libcurl"))) (use-foreign-library libcurl)

  15. Example • Using variables (defctype curl-code :int) ;;; Initialize libcurl with FLAGS. (defcfun "curl_global_init" curl-code (flags :long)) (defctype easy-handle :pointer) (foreign-funcall "curl_easy_setopt" :pointer *easy-handle* curl-option :nosignal :long 1 curl-code)

  16. Connection to the machine • How does Lisp work? • C Program or • From stack overflow (defx86lapmacro %car (src dest) (target-arch-case (:x8632 `(movl (@ x8632::cons.car (% ,src)) (% ,dest))) (:x8664 `(movq (@ x8664::cons.car (% ,src)) (% ,dest)))))

  17. Investigate • How does Lisp work? Two functions show how • (disassemble ‘functionName) • Turn on trace • (trace functionName) • Run functionName and see what happens (defunfactorial (n) (if (plusp n) (* n (factorial (1- n))) 1))

  18. Others • SWIG • C/C++ Program that allows for multiple languages to execute said code • Example • VR Toolkit • Scripting to work with small parts of the project

  19. Next week • Midterm exam • Prolog • Project 1

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