CODEWITHSUNDEEP
programming-languagesprogram-flow
Axarydax
Axarydax

Reputation: 16603

Programming language without ELSE keyword - is it more complicated?

I'm working on a simple programming language for kids, based on Karel. For controlling program flow, I currently provide these facilities (in pseudocode):

I don't have any means to return from a procedure, and I don't provide the else statement.

Take the following code for an example:

if something
 statement1
if not something
 statement2

The execution of code flows to if, executing statement1 if something is true; then testing if something is not true (but the state of the program has changed!), then executing statement2. This can lead to both tests succeeding.

Does this limit the programmer? So far I've been able to solve all of my example problems by just using if ... if not ..., or using if not first, then if.

So, my question is: Is adding the else statement necessary? It would make the language a bit more complicated with having more keywords. Are all problems that would be solvable with else statement solvable also without it, albeit more complicated?

Or is omitting the else statement actually making the language more complicated and counter-intuitive?

Upvotes: 1

Views: 755

Answers (4)

Mark Byers
Mark Byers

Reputation: 838276

If something is expensive to evaluate then your language with else might give a problem because the evaluation will be performed twice.

Another potential problem is that if statement1 can modify the value of something you may end up with both tests succeeding - something that could not happen if you used else.

Of course these problems can be mitigated by storing the result in a temporary local variable:

bool result = something
if result
    statement1
if not result
    statement2

So no you aren't limiting the programmer in what is possible - everything that can be done with else can be done without it by using the above approach. But it is a little more code to write each time and it introduces a few new potential problems for the unwary programmer that would be avoided if you allowed else.

Upvotes: 4

Jack
Jack

Reputation: 133587

Semantically speaking you could avoid having the else construct, but from practical point of view I don't see any necessity of doing that.

The concept of do something if something is true, otherwise something else is not so strange and confusing, it sounds actually quite straightforward that having to evaluate and negate an expression again just to check its negation.. it's a free (in sense of "with no added complexity") optional synctactic sugar that is automatic when developing a language.

I saw many other features really more useless compared to the else statement.. then you are not considering the fact that evaluating a condition twice maybe harmful for side-effects or for complexity (wasted cpu?) or for the fact itself that you already have calculated it and you have to do it again for a lack of the language not because it's senseful.

Upvotes: 3

The Smallest
The Smallest

Reputation: 5773

IMHO It's bad idea to teach children to duplicate code.

Upvotes: 1

John Percival Hackworth
John Percival Hackworth

Reputation: 11531

If something has side-effects than your approach will cause them to happen twice, which is probably not what you want.

Upvotes: 2

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