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ECS140A-L6

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📗 -> 10/14/25: ECS140A-L6

Lecture Slide Link

🎤 Vocab

❗ Unit and Larger Context

Small summary

✒️ -> Scratch Notes

Lisp

  • Functional prog lang
  • Originally intended for AI apps
  • Stands for “LISt Processesing”
  • Many variants
    • MacLisp
    • Scheme
    • Franz Lisp
    • Common LISP
  • We use Common LISP (CLISP)

Outline

  • Basic list operations (car, cdr, cons , list)
  • User-defined functions (defun)
  • Predicates (atom, null, equal, etc.)
  • Basic Lisp constructs
    • if
    • cond
    • let and let*
    • quote, eval, funcall, apply
  • Lambda functions
  • High-order functions (mapcar, mapc, maplist)
  • Closures

s-expressions

Everything is a symbolic expression

  • Atoms - not viewed as having parts

    • Numbers, symbols

  • Lists - constructed from atoms and lists

    • Empty list: nil or ()
    • Constructed lists: (* 2 3), (1 (a 2) 3)
      Computation performed through evaluation

  • Numbers evaluate to themselves

  • Symbols evaluate to last bound value

  • Lists: first function, rest args to that function, evaluates to resulting value of function

  • Specific rules for special forms like setq, quote, etc.

Declaration - setq

One way to assign value to symbol:

  • (setq x 5) - Assigns value of 5 to x
Quote

Special function that takes one argument, which is not evaluated
Can be used when we want to stop lisp from evaluating something

(quote (a b c)) -> // (A B C)
'(ab b c) -> (A B C)
List Ops

car - Returns first element (head) of a list
cdr - returns the remaining elements (tail) of a list

In order to use, list passed in needs to be quote. Otherwise, fails

cons - returns the list obtained by taking the second argument and sticking the first on in front of it

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