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cs2370 Notes: 05 Functions

·2 mins

We’ve been using functions for a while, but where do they come from?

def add2(xx):
    return xx + 2

And that’s the whole story, any questions?

Maybe it’s a bit more complicated than that.

def square(xx):
    return xx * xx


def sqrt(xx):
    guess = 1
    while square(square(guess) - xx) > 0.01:
        guess = 0.5 * (guess + xx / guess)
    return round(guess, 1)

Two basic kinds of functions:

def say_hello(name):
    print("Hello,", name)
    # return None
  • Functions that do stuff are said to have side effects.
  • Functions that just compute and return a value are said to be pure.
  • Functions that only exit for their side effects aren’t really “functions” - other languages might call them procedures or subroutines.

Designing a function: #

  • Purpose statement
  • Signature (e.g. int -> int)
  • Examples
  • Stub
  • Standard pattern
  • Asserts

Design a function to:

  • Convert Farenheight to Celsius
    • °C = (°F - 32) × 5/9
  • Given a numeric grade and the syllabus, determine if we passed the class
  • Reverse a string with a loop and an accumulator
    • Standard pattern: Single item or sequence?
    • For sequence, a for loop
  • Given a numeric grade and the syllabus, determine the letter grade (just the letter part)
  • Given two sports teams and their scores (t1, s1, t2, s2), determine which team won the game.
  • Print a square of a given size with “+-|” characters.