I recently attended BuildStuff for the first time thanks to my company Small Improvements. I can’t remember the last time I came back from a conference so invigorated and full of learning. I wrote a post about it over on the Small Improvements tech blog but here’s something that didn’t make it into that post.
This is what Kevlin Henney argued during his well received talk. Kevlin is a fantastically clever guy and his talks are always entertaining as well as thought provoking. Although the talk was mostly a history of procedural programming languages (everyone in the audience was geeking out over Algol68), there were a couple of takeaways that stuck in my mind.
Guard clauses can be misused, the procedural if-else block is actually more readable.
Take a look at this
public Integer add(Integer a, Integer b){
if(a==null && b==null) {
return null;
}
if(a==null) {
return b;
}
if(b==null) {
return a;
}
return a + b;
}
Now collapse the if statements
if(a==null && b==null)...
if(a==null)...
if(b==null)...
return a + b;
It’s hard to surmise the logic from here as we don’t know whether the if statements will mutate the state of a or b.
Consider the alternative
public Integer add(Integer a, Integer b){
if(a==null && b==null) {
return null;
} else if(a==null) {
return b;
} else if(b==null) {
return a;
} else {
return a + b;
}
}
This is a lot easier to reason about even when we collapse the if-else blocks
if(a==null && b==null)...
else if(a==null)...
else if(b==null)...
else ...
By adding the else clauses we tell the reader that we only fall into the logic if none of the other clauses are met.