# Let's put a smile on that face of yours!

I am so optimistic, as happy as can be,
But deep inside darkness, violence you may see.
To half the population, danger is my name,
For after an encounter, they never are the same.

For others I'm just there, don't really do too much,
I tend to vanish quickly, without a single touch.
But all I trap inside of me, as I contemplate,
And soon they're free to go, without that which I hate.

Determine now who I am, and what it is I do,
Who fears me, who doesn't care? Am I one or two?

I'm thinking you're

the absolute value function. That is, |(+/-)x|, where if x is negative, it becomes positive (losing the negative sign, which you hate), but if x is already positive, nothing happens.

I am so optimistic, as happy as can be,

Literally 100% positive

But deep inside darkness, violence you may see.

Negative numbers can be held inside the function before they're converted

To half the population, danger is my name,

all negative numbers

For after an encounter, they never are the same.

they become positive

For others I'm just there, don't really do too much,

positive numbers don't change

I tend to vanish quickly, without a single touch.

nothing happens

But all I trap inside of me, as I contemplate,

nothing escapes the function. dun dun dunnnn.

And soon they're free to go, without that which I hate.

no negative sign

Determine now who I am, and what it is I do, Who fears me, who doesn't care? Am I one or two?

negative numbers fear the operation, positive numbers don't.

• Very nicely done. This is the intended answer. Commented Aug 14, 2015 at 17:26
• @AggieKidd I have an alternative answer, but it's ... um, dirty-minded. It fits everything, but I'm not sure if I should put it up in case it gets flagged as offensive or something! Commented Aug 14, 2015 at 19:29
• @randal'thor Go for it! What's the worst that can happen? It gets deleted? Commented Aug 14, 2015 at 19:31
• I think we can already tell what you mean lol. Commented Aug 14, 2015 at 19:32

You are a

Dentist

I am so optimistic, as happy as can be

Dentist are usually happy people, and they like smiles.

But deep inside darkness, violence you may see.

It is dark in your mouth, which is where the dentist's work is done. Depending on the status of your oral hygiene, the dentist's work might be violent, with bleeding gums and worse commonplace (not that I know from experience...).

To half the population, danger is my name, For after an encounter, they never are the same.

A surprising number of people are afraid of going to the dentist, due to the pain that they expect and sometimes receive on visiting. A dentist may leave someone "never the same" by pulling teeth, whether molars or otherwise, drilling, putting in caps, or just scaring the patient even more severely.

For others I'm just there, don't really do too much, I tend to vanish quickly, without a single touch.

Those with good oral hygiene may actually see the dentist for no more than a minute. The dental hygienist does most of the cleaning and inspection, which the true dentist just pops in to double-check.

But all I trap inside of me, as I contemplate, And soon they're free to go, without that which I hate.

I think this just refers to all that go to the dentist, not ALL IN EXISTENCE, so: Everyone that goes to the dentist has their teeth cleaned of plaque and gingivitis, which is what the dentist hates the most.

Determine now who I am, and what it is I do, Who fears me, who doesn't care? Am I one or two?

You are the dentist and hygienist, and you both clean teeth, but one more than the other. Those with good teeth don't care, those with bad teeth do. You are two who say "Let's put a smile on that face of yours!"

I'll also say that:

An orthodontist changes people, too, and could be said to hate crooked teeth, but people leave the orthodontist with braces, not straight teeth, and they leave the dentist with clean teeth. With that, I think dentist better fits the bill.

• +1 for a great attempt. Not quite though. When I say half the population, I mean 1/2 of the population. Commented Aug 14, 2015 at 16:20
• @AggieKidd you sure you don't mean 49 or 51%? Commented Aug 14, 2015 at 16:31
• @Goinghamateur One could argue I don't mean exactly half, but it is about as close as one could get without being exactly. Commented Aug 14, 2015 at 16:34