Maxi Contieri

Posted on Nov 14, 2020 • Updated on Jul 6, 2021 • Originally published at maximilianocontieri.com

Code Smell 24 - Boolean Coercions

#oop #tutorial #boolean #coercion

Booleans should be just True and false

TL;DR: Don't do magic castings to boolean. You will regret on a friday night.

Problems

Hiding Errors
Accidental complexity coupled to one particular language.
Readability
Difficulty to hop among languages.
IFs

Solutions

Be explicit.
Work with booleans for boolean conditions. Not integers, not nulls, not strings, not lists. Just booleans.
Fail fast

Sample Code

Wrong

virus = ['MERS', 'SARS']
vaccines = []

if vaccines:
    print ("let's get vaccinated")
else:
    print ("We have no vaccines yet. Keep researching")

if virus:
    print ("There are some virus around. Take extra care")
else:
    print ("We are free to get out. Not masks are necessary")

#equivalent     

if not vaccines:
    print ("We have no vaccines yet. Keep researching")
else:
    print ("let's get vaccinated")

if not virus:
    print ("We are free to get out. Not masks are necessary")
else:
    print ("There are some virus around. Take extra care")

Right

if len(vaccines) == 0:
    print ("We have no vaccines yet. Keep researching")
else:
    print ("Let's get vaccinated")


if len(virus) == 0:
    print ("We are free to get out. Not masks are necessary")
else:
    print ("There are some virus around. Take extra care")

Detection

This is a language feature. Some strict languages show warnings with this magic wizardry.

Conclusion

Some languages encourage doing some magic abbreviations and automatic castings. This is a source of errors and a Premature Optimization warning.

We should always be as explicit as possible.

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It is not the language that makes programs appear simple. It is the programmer that make the language appear simple!

Robert Martin

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Last update: 2021/07/07

Discussion (17)

Junxiao Shi • Nov 14 '20

Go doesn't allow conversions from and to boolean type altogether.

Meanwhile in C, it's normal to test an integer as boolean, but I'd rather write if (i == 0) although I know the compile will optimize the comparison away.

Eljay-Adobe • Nov 14 '20

Shouldn't that be if (i != 0) ...?

Maxi Contieri • Nov 14 '20

what is 'i' ?

what real world entity does it represent ? the letter 'i' ? Why would you compare a letter with a number ?

DarkWiiPlayer • Nov 14 '20

Considering the example talks about C, i is probably a counter variable for a numeric loop.

Maxi Contieri • Nov 14 '20

i think we should name it 'counter' or 'index'
We are doing software, not math

Junxiao Shi • Nov 14 '20

My real code uses the variable name res.
github.com/usnistgov/ndn-dpdk/blob...

int res = rte_hash_add_key_with_hash_data(pcct->tokenHt, &token, hash, entry);
if (likely(res == 0)) {
  break;
}

That likely is not "premature optimization". This code is for a high speed router that processes millions of packets per second.

Maxi Contieri • Nov 14 '20

I don't know what 'res' stands for.

But if you performed a real benchmark on the code and found out it really needed to be optimized it does not classify as 'premature'.
I'm ok with that since in this very special case speed is more important than readability

Junxiao Shi • Nov 14 '20

res means result. It is common in C code.

Maxi Contieri • Nov 15 '20 • Edited on Nov 15

ok. that's why i don't like low level languages. They are more cryptic.
I try to specialize on higher level languages. Most code smells apply to them.

I suggest not to use 'res' 'i' ir 'result' as variable names since they have no business meaning.

more examples here:

maximilianocontieri.com/what-exact...

DarkWiiPlayer • Nov 15 '20

certain things like res and i are so common that I'd consider them expressive variable names, but there's not many. For res, I really like the pascal feature of assigning to the subroutines name, because presumably that's already a descriptive name for the result value.

re not liking low level languages, it seems to me like high- and low-level languages have completely different appeals (I happen to like both of them), so one might like one but not the other. Thinking in systems and poking at bits are as much different areas as back-end and front-end.

Maxi Contieri • Nov 15 '20

you are absolutely right. They are different tools for different purposes

Junxiao Shi • Nov 14 '20

Depending on whether you want true or false. I usually test for error condition and return early.

Maxi Contieri • Nov 14 '20

Exactly ! Let the compiler do it for you if it is safe.
Go is much stricter than C. I think Go lacks several important features like Exceptions or Full Closures. Once it catches up with older languages it would be an excellent option

DarkWiiPlayer • Nov 14 '20

I hate languages that treat "empty" values as falsey. It's dumb and leads to unexpected errors. An empty array is still an array, an empty string is still a string, zero is still a number. Neither of them has anything "false" about them and languages that treat them as such are just poorly designed (low-level languages like C being the exception, for obvious reasons)

DarkWiiPlayer • Nov 14 '20

I really prefer how this would work in ruby:

if vaccines.empty?
   puts "We have no vaccines yet. Keep researching"
else
   puts "Let's get vaccinated"

It's closer to human thinking.

Maxi Contieri • Nov 14 '20

i agree.

empty is much better than strlen()=0

Alain Van Hout • Nov 14 '20

I'm a bit confused here. You say to not use coercion, but your 'right' example treats an array as a boolean.

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Code Smell 24 - Boolean Coercions

Problems

Solutions

Sample Code

Wrong

Right

Detection

Tags

Conclusion

Relations

Code Smell 06 - Too Clever Programmer

Maxi Contieri ・ Oct 25 '20 ・ 2 min read

Code Smell 69 - Big Bang (JavaScript Ridiculous Castings)

Maxi Contieri ・ May 4 '21 ・ 2 min read

More Info

Fail Fast

Maxi Contieri ・ Dec 6 '20 ・ 6 min read

Software Engineering Great Quotes

Maxi Contieri ・ Dec 28 '20 ・ 13 min read

How to Find the Stinky parts of your Code

Maxi Contieri ・ May 21 '21 ・ 4 min read

Discussion (17)

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