programming_presentation/presentation-low-level-stuff.adoc at master

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what is good code?

good code

It works
Is easy to understand
Is easy to change

Bad code: code smells

Duplicated code
Unnecessary complexity
A single change needs to be applied in many places at the same time.
Methods do too many things
Too many nested if / loops
Too many parameters
…

How to improve code quality?

Refactoring is the process of changing a software system in such a way that it does not alter the function of the code yet improves its internal structure.

— Martin Fowler
Refactoring: Improving the Design of Existing Code (1999)

KISS

Keep it Simple, Stupid

Avoid code duplication

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Probably the most common and worst mistake in programming
Avoid at all cost!

refactoring code duplication

def f1():
  # read file
  ...
  # use complex method to calculate a

def f2():
  # read file
  ...
  # use complex method to calculate b

def read_file()
def complex_method()

def f1():
  read_file()
  complex_method(a)

def f2():
  read_file()
  complex_method(b)

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def f1():
  # read file
  ...
  # calculate a

def f2():
  # read file
  ...
  # calculate b

def higher_function()
    if (condition)
        f1()
    else
        f2()

def read_file()
def complex_method()

def higher_function()
    read_file()
    if (condition)
        complex_method(a)
    else
        complex_method(b)

A special case

def f1():
  # same code
  ...
  # method 1
  ...
  # same code

def f2():
  # same code
  ...
  # method 2
  ...
  # same code

def method_1():
    ...
def method_2():
    ...

#functions are just another type of objects!
def f(in_method):
  # same code
  ...
  in_method()
  ...
  # same code

def higher_function():
    f(method_1)
    f(method_2)

Each function should do one thing

“The first rule of functions is that they should be small. The second rule of functions is that they should be smaller than that”

size is not everything!

def function_1():
  # code here
  return function_2(results_1)

def function_2(input_2):
  # code here
  return function_3(results_2)

def function_3(input_3):
  # code here
  return function_4(results_3)

def function_4(input_4):
  # code here
  return results_4

def main_function():
  results_1 = function_1()
  results_2 = function_2(results_1)
  results_3 = function_3(results_2)
  return function_4(results_3)

Use comments

Proper use of commenting can

make code maintenance much easier
help finding bugs faster
make your code more readable to other people
make your code more readable to yourself (in six months)

Don’t over-comment your code

comments are a necessary evil
comments cover up naming failures
comments must evolve with code

when and how to write comments

Always try to explain yourself in code.
Don’t be redundant.
Use them in complex expressions.
Use as explanation of intent.
Use as clarification of code.
Use as warning of consequences.
Don’t comment out code: remove it (and use version control)

Naming Conventions

Use names that are easy to understand.
Format them consistently.
Names must help understanding what a piece of code does.
Avoid single variable names.

example: replacing comments with good naming

# This function calculates prices, compares to sales
# promotions, checks if prices are valid,
# then send an email of promotion to user
def doSomeThings():

  # Calculate prices
  ...
  ...
  # Compare prices with sales promotions
  ...
  ...
  # Check if calculated prices are valid
  ...
  ...
  # Send promotions to users
  ...
  ...

def sendPromotionEmailToUsers():
  calculatePrices();
  comparePricesWithSalesPromotions();
  checkIfCalculatedPricesAreValid();
  sendPromotionEmail();

keep a consistent format

useCamelCase
OrPascalCase
or_snake_case
or-kebab-case
But not all of them together

def my_function():
  print("Hello in a function")

def myFunction():
  print("Ey, I'm a different function")

def my-Function():
  print("I'm yet another function, good luck choosing the right one")

def my_FunctionIs-A-Terrible_mess():
  print("Imagine how things turn when you have several thousand lines of code...")

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Some languages (ex. python) have a "standard" pep 08 format, check it out!

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