Seven Ineffective Habits of Many Programmerssddconf.com/brands/sdd/library/Seven_Ineffective_Coding_Habits_of... · Signal-to-noise ratio (often abbreviated SNR or S/N) is a measure

Seven Ineffective

Coding Habits of

Many Programmers

@KevlinHenney

It turns out that style

matters in programming

for the same reason that

it matters in writing. It

makes for better reading.

Noisy Code

Signal-to-noise ratio (often abbreviated SNR or

S/N) is a measure used in science and engineering

that compares the level of a desired signal to the

level of background noise.

Signal-to-noise ratio is sometimes used informally

to refer to the ratio of useful information to false or

irrelevant data in a conversation or exchange.

http://en.wikipedia.org/wiki/Signal_to_noise_ratio

To be, or not to be: that is the question:

Whether 'tis nobler in the mind to suffer

The slings and arrows of outrageous fortune,

Or to take arms against a sea of troubles,

And by opposing end them?

William Shakespeare

Hamlet

Continuing existence or cessation of

existence: those are the scenarios. Is it

more empowering mentally to work towards

an accommodation of the downsizings and

negative outcomes of adversarial

circumstance, or would it be a greater

enhancement of the bottom line to move

forwards to a challenge to our current

difficulties, and, by making a commitment

to opposition, to effect their demise?

Tom Burton

Long Words Bother Me

public class RecentlyUsedList { private List<string> items; public RecentlyUsedList() { items = new List<string>(); } public void Add(string newItem) { if (items.Contains(newItem)) { int position = items.IndexOf(newItem); string existingItem = items[position]; items.RemoveAt(position); items.Insert(0, existingItem); } else { items.Insert(0, newItem); } } public int Count { get { int size = items.Count; return size; } } public string this[int index] { get { int position = 0; foreach (string item in items) { if (position == index) return item; ++position; } throw new ArgumentOutOfRangeException(); } } }

public class RecentlyUsedList { private List<string> items; public RecentlyUsedList() { items = new List<string>(); } public void Add(string newItem) { if (items.Contains(newItem)) { int position = items.IndexOf(newItem); string existingItem = list[position]; items.RemoveAt(position); items.Insert(0, existingItem); } else { items.Insert(0, newItem); } } public int Count { get { int size = items.Count; return size; } } public string this[int index] { get { int position = 0; foreach (string value in items) { if (position == index) return value; ++position; } throw new ArgumentOutOfRangeException(); } } }

public class RecentlyUsedList { private List<string> items = new List<string>(); public void Add(string newItem) { items.Remove(newItem); items.Add(newItem); } public int Count { get { return items.Count; } } public string this[int index] { get { return items[Count - index - 1]; } } }

Comments

A delicate matter, requiring taste and judgement. I tend to err on the side of eliminating comments, for several reasons. First, if the code is clear, and uses good type names and variable names, it should explain itself. Second, comments aren't checked by the compiler, so there is no guarantee they're right, especially after the code is modified. A misleading comment can be very confusing. Third, the issue of typography: comments clutter code.

Rob Pike, "Notes on Programming in C"

There is a famously bad comment style:

i=i+1; /* Add one to i */

and there are worse ways to do it:

/**********************************

* *

* Add one to i *

* *

**********************************/

i=i+1;

Don't laugh now, wait until you see it in real life.

Rob Pike, "Notes on Programming in C"

A common fallacy is to assume authors of incomprehensible code will somehow be able to express themselves lucidly and clearly in comments.

Kevlin Henney https://twitter.com/KevlinHenney/status/381021802941906944

Unsustainable Spacing

To be, or not to be: that is the question:

Whether 'tis nobler in the mind to suffer

The slings and arrows of outrageous fortune,

Or to take arms against a sea of troubles,

And by opposing end them?

William Shakespeare

Hamlet

Continuing existence or cessation of

existence: those are the scenarios. Is it

more empowering mentally to work towards

an accommodation of the downsizings and

negative outcomes of adversarial

circumstance, or would it be a greater

enhancement of the bottom line to move

forwards to a challenge to our current

difficulties, and, by making a commitment

to opposition, to effect their demise?

Tom Burton

Long Words Bother Me

Continuing existence or cessation of existence:

those are the scenarios. Is it

more empowering mentally

to work towards an

accommodation of the

downsizings and negative

outcomes of adversarial

circumstance, or would it be

a greater enhancement of

the bottom line to move

forwards to a challenge to

our current difficulties, and,

by making a commitment to

opposition, to effect their

demise?

How many programmers lay out their code

Column 80

How people read

To answer the question "What is clean design?"

most succinctly: a clean design is one that

supports visual thinking so people can meet their

informational needs with a minimum of

conscious effort.

Daniel Higginbotham ∙ "Clean Up Your Mess — A Guide to Visual Design for Everyone" ∙ http://www.visualmess.com/

You convey information by the way you arrange

a design's elements in relation to each other. This

information is understood immediately, if not

consciously, by the people viewing your designs.


This is great if the visual relationships are

obvious and accurate, but if they're not, your

audience is going to get confused. They'll have to

examine your work carefully, going back and

forth between the different parts to make sure

they understand.


public int howNotToLayoutAMethodHeader(int firstArgument,

String secondArgument)

public int ensureArgumentsAreAlignedLikeThis(

int firstArgument,


public int orEnsureArgumentsAreGroupedLikeThis(

int firstArgument, String secondArgument)

public int butNotAlignedLikeThis(int firstArgument,


int doNotFormat = likeThis(someArgumentOrExpression,

anotherArgumentOrExpression);

int insteadFormat =

somethingLikeThis(

someArgumentOrExpression,


int orFormat = somethingLikeThis(



int asItIs = unstable(someArgumentOrExpression,


int butThisIs =

stable(



int andThisIs = stable(



public ResultType arbitraryMethodName(FirstArgumentType firstArgument,

SecondArgumentType secondArgument,

ThirdArgumentType thirdArgument) {

LocalVariableType localVariable = method(firstArgument,

secondArgument);

if (localVariable.isSomething(thirdArgument,

SOME_SHOUTY_CONSTANT)) {

doSomethingWith(localVariable);

}

return localVariable.getSomething();

}

public ResultType arbitraryMethodName(

FirstArgumentType firstArgument,



LocalVariableType localVariable =

method(firstArgument, secondArgument);

if (localVariable.isSomething(

thirdArgument, SOME_SHOUTY_CONSTANT)) {

doSomething(localVariable);

}


}

XXXXXX XXXXXXXXXX XXXXXXXXXXXXXXXXXXX

XXXXXXXXXXXXXXXXX XXXXXXXXXXXXX

XXXXXXXXXXXXXXXXXX XXXXXXXXXXXXXX



XXXXXX XXXXXXXXXXXXX XXXXXXXXXXXXXX

XX XXXXXXXXXXXXX XXXXXXXXXXX

XXXXXXXXXXXXX XXXXXXXXXXXXXXXXXXXX

XXXXXXXXXXX XXXXXXXXXXXXX

XXXXXX XXXXXXXXXXXXX XXXXXXXXXXXX








thirdArgument, SOME_SHOUTY_CONSTANT)) {


}


}














ThirdArgumentType thirdArgument)

{




thirdArgument, SOME_SHOUTY_CONSTANT))

{


}


}











Lego Naming

Agglutination is a process in linguistic morphology

derivation in which complex words are formed by

stringing together morphemes, each with a single

grammatical or semantic meaning. Languages that

use agglutination widely are called agglutinative

languages.

http://en.wikipedia.org/wiki/Agglutination

pneumonoultramicroscopicsilicovolcanoconiosis

Rindfleischetikettierungsüberwachungsaufgabenübertragungsgesetz

fylkestrafikksikkerhetsutvalgssekretariatslederfunksjonene

Proxy

validate

Service

Value

get

create

Manager

check

Controller

set

Factory

Object

do enable

process

disable

Exception

add

remove

https://twitter.com/KevlinHenney/status/476962681636020224

https://twitter.com/KevlinHenney/status/476963022549032960

People will be using the

words you choose in their

conversation for the next 20

years. You want to be sure

you do it right.

Unfortunately, many people

get all formal [...]. Just calling

it what it is isn't enough.

public interface ConditionChecker { boolean checkCondition(); ... }

public interface Condition { boolean isTrue(); ... }

They have to tack on a

flowery, computer science-y,

impressive sounding, but

ultimately meaningless word,

like Object, Thing,

Component, Part, Manager,

Entity, or Item.

The simple, the punchy, the

easily remembered will be

far more effective in the long

run than some long name

that says it all, but in such a

way that no one wants to

say it at all.

AccessViolationException

ArgumentOutOfRangeException

ArrayTypeMismatchException

BadImageFormatException

CannotUnloadAppDomainException

EntryPointNotFoundException

IndexOutOfRangeException

InvalidOperationException

OverflowException

AccessViolation

ArgumentOutOfRange

ArrayTypeMismatch

BadImageFormat

CannotUnloadAppDomain

EntryPointNotFound

IndexOutOfRange

InvalidOperation

Overflow

ArgumentException

ArithmeticException

ContextMarshalException

FieldAccessException

FormatException

NullReferenceException

ObjectDisposedException

RankException

TypeAccessException

Argument

Arithmetic

ContextMarshal

FieldAccess

Format

NullReference

ObjectDisposed

Rank

TypeAccess

InvalidArgument

InvalidArithmeticOperation

FailedContextMarshal

InvalidFieldAccess

InvalidFormat

NullDereferenced

OperationOnDisposedObject

ArrayRankMismatch

InvalidTypeAccess

Omit needless words.

William Strunk and E B White

The Elements of Style

Underabstraction

http://fragmental.tw/2009/04/29/tag-clouds-see-how-noisy-your-code-is/

http://fragmental.tw/2009/04/29/tag-clouds-see-how-noisy-your-code-is/

if (portfolioIdsByTraderId.get(trader.getId()) .containsKey(portfolio.getId())) { ... }

Dan North, "Code in the Language of the Domain" 97 Things Every Programmer Should Know

if (trader.canView(portfolio)) { ... }

Dan North, "Code in the Language of the Domain" 97 Things Every Programmer Should Know

parser.processNodes(text, false);

Gregor Hohpe, "Convenience Is Not an -ility" 97 Things Every Programmer Should Know

If you have a procedure with

ten parameters, you probably

missed some.

Alan Perlis

Unencapsulated State

public class RecentlyUsedList { private List<string> items = new List<string>();

public List<string> Items { get { return items; } } public void Add(string newItem) { if(newItem == null) throw new ArgumentNullException(); items.Remove(newItem); items.Insert(0, newItem); } ... }





var list = new RecentlyUsedList();

list.Add("Hello, World!");

Console.WriteLine(list.Items.Count);

list.Items.Add("Hello, World!");

Console.WriteLine(list.Items.Count);

list.Items.Add(null);

Don't ever invite a

vampire into your

house, you silly boy.

It renders you

powerless.

public class RecentlyUsedList { private IList<string> items = new List<string>();

public int Count { get { return items.Count; } } public string this[int index] { get { return items[index]; } } public void Add(string newItem) { if(newItem == null) throw new ArgumentNullException(); items.Remove(newItem); items.Insert(0, newItem); } ... }

public class RecentlyUsedList { private IList<string> items = new List<string>();

public int Count { get { return items.Count; } } public string this[int index] { get { return items[Count – index - 1]; } } public void Add(string newItem) { if(newItem == null) throw new ArgumentNullException(); items.Remove(newItem); items.Add(newItem); } ... }

Getters and Setters

public class Money implements ... { ... public int getUnits() ... public int getHundredths() ... public Currency getCurrency() ... ... public void setUnits(int newUnits) ... public void setHundredths(int newHundredths) ... public void setCurrency(Currency newCurrency) ... ... }

public final class Money implements ... { ... public int getUnits() ... public int getHundredths() ... public Currency getCurrency() ... ... }

Just because you have a getter, doesn't mean you should have a setter.

public final class Money implements ... { ... public int getUnits() ... public int getHundredths() ... public Currency getCurrency() ... ... }

public final class Money implements ... { ... public int units() ... public int hundredths() ... public Currency currency() ... ... }

"Get something" is an imperative with an expected side effect.

Uncohesive Tests

Everybody knows that TDD stands for Test Driven Development. However, people too often concentrate on the words "Test" and "Development" and don't consider what the word "Driven" really implies. For tests to drive development they must do more than just test that code performs its required functionality: they must clearly express that required functionality to the reader. That is, they must be clear specifications of the required functionality. Tests that are not written with their role as specifications in mind can be very confusing to read.

Nat Pryce and Steve Freeman "Are Your Tests Really Driving Your Development?"

public class RecentlyUsedList { ... public RecentlyUsedList() ... public int Count { get... } public string this[int index] { get... } public void Add(string newItem) ... ... }

[TestFixture] public class RecentlyUsedListTests { [Test] public void TestConstructor() ... [Test] public void TestCountGet() ... [Test] public void TestIndexerGet() ... [Test] public void TestAdd() ... ... }

method test

test

test

method

method

test

test

namespace RecentlyUsedList_spec { [TestFixture] public class A_new_list { [Test] public void Is_empty() }

[TestFixture] public class An_empty_list { [Test] public void Retains_a_single_addition() [Test] public void Retains_unique_additions_in_stack_order() }

[TestFixture] public class A_non_empty_list { [Test] public void Is_unchanged_when_head_item_is_readded() [Test] public void Moves_non_head_item_to_head_when_it_is_readded() }

[TestFixture] public class Any_list_rejects { [Test] public void Addition_of_null_items() [Test] public void Indexing_past_its_end() [Test] public void Negative_indexing() } }

namespace RecentlyUsedList_spec { [TestFixture] public class A_new_list { [Test] public void Is_empty() }

[TestFixture] public class An_empty_list { [Test] public void Retains_a_single_addition() [Test] public void Retains_unique_additions_in_stack_order() }

[TestFixture] public class A_non_empty_list { [Test] public void Is_unchanged_when_head_item_is_readded() [Test] public void Moves_non_head_item_to_head_when_it_is_readded() }

[TestFixture] public class Any_list_rejects { [Test] public void Addition_of_null_items() [Test] public void Indexing_past_its_end() [Test] public void Negative_indexing() } }

So who should you be writing the tests for? For the person trying to understand your code.

Good tests act as documentation for the code they are testing. They describe how the code works. For each usage scenario, the test(s):

Describe the context, starting point, or preconditions that must be satisfied

Illustrate how the software is invoked

Describe the expected results or postconditions to be verified

Different usage scenarios will have slightly different versions of each of these.

Gerard Meszaros "Write Tests for People"

namespace RecentlyUsedList_spec { [TestFixture] public class A_new_list ...

[TestFixture] public class An_empty_list { [Test] public void Retains_a_single_addition( [Values("London", "Bristol", "Oslo")] string addend) { var items = new RecentlyUsedList(); // Given...

items.Add(addend); // When...

Assert.AreEqual(1, items.Count); // Then... Assert.AreEqual(addend, list[0]); } [Test] public void Retains_unique_additions_in_stack_order() }

[TestFixture] public class A_non_empty_list ...

[TestFixture] public class Any_list_rejects ... }

One of the things that Osherove warns against is multiple asserts in unit tests.

Owen Pellegrin http://www.owenpellegrin.com/blog/testing/how-do-you-solve-multiple-asserts/

string[] itinerary = ...;

string[] expected =

{

"London", "Bristol", "Oslo"

};

Assert.AreEqual(expected, itinerary);

Assert.IsNotNull(itinerary);

Assert.AreEqual(3, itinerary.Length);

Assert.AreEqual("London", itinerary[0]);

Assert.AreEqual("Bristol", itinerary[1]);

Assert.AreEqual("Oslo", itinerary[2]);

Assert.DoesNotThrow(() =>

{

string[] itinerary = ...;

string[] expected = ...;

});

My guideline is usually that you test one logical concept per test. You can have multiple asserts on the same object. They will usually be the same concept being tested.

Roy Osherove http://www.owenpellegrin.com/blog/testing/how-do-you-solve-multiple-asserts/

A test case should be just that: it should correspond to a single case.

One of the most foundational principles of good design is:

Gather together those things that change for the same reason, and separate those things that change for different reasons.

This principle is often known as the single responsibility principle, or SRP. In short, it says that a subsystem, module, class, or even a function, should not have more than one reason to change.

We refer to a sound line of reasoning,

for example, as coherent. The thoughts

fit, they go together, they relate to each

other. This is exactly the characteristic

of a class that makes it coherent: the

pieces all seem to be related, they seem

to belong together, and it would feel

somewhat unnatural to pull them apart.

Such a class exhibits cohesion.

We refer to a sound line of reasoning,

for example, as coherent. The thoughts

fit, they go together, they relate to each

other. This is exactly the characteristic of

a test that makes it coherent: the pieces

all seem to be related, they seem to

belong together, and it would feel

somewhat unnatural to pull them apart.

Such a test exhibits cohesion.

class tests

tests class tests

tests

At some level

the style

becomes the

substance.

Documents

Seven Ineffective Habits of Many Programmerssddconf.com/brands/sdd/library/Seven_Ineffective_Coding_Habits_of... · Signal-to-noise ratio (often abbreviated SNR or S/N) is a measure