Name: Why TRUE + TRUE = 2: Data Types
Uploaded: 2020-04-01T01:20:09.000Z
Duration: 8 min 8 s
Description: Thousands of YouTube videos with English-Chinese subtitles! Now you can learn to understand native speakers, expand your vocabulary, and improve your pronunciation...

Adverbs of degree

programmers needed to be very sure about the data they were operating on.

Basic passive voice

If an operation was fed a number when it was expecting a letter, a character:

at best you might get a garbled response,

and at worst you could break the system. Maybe even physically.

Now, at the low level of coding, yeah, that's still true.

But these days we have programming languages where

we don't always need to be so rigorous in defining the data,

and we can let the computer figure it out.

But for something that seems so technical, this can be controversial.

When you write a computer program, you use variables,

which are basically just labelled buckets of memory.

Inside that bucket is some data, and you can change it,

but computer memory is a bit like an enormous rack of switches

storing ones and zeros that represent other things like letters and numbers.

there is nothing in there to indicate what those ones and zeros are actually representing.

So in the code, we declare that the variable is a particular type.

What's contained in that variable, in that bucket?  It's an integer.

What's in that one? It's a string of characters.

That tells the computer how to interpret those ones and zeros in memory.

The types that you get to use can differ a bit between languages.

But in general, you'll at least have: Integer or INT.

That's a whole number that can't have anything after the decimal point.

And those are extremely useful for storing things like

the number of times you've looped through some code,

or how many points your player's clocked up,

or how many pennies there are in someone's account.

These are letters, numbers, punctuation, and whitespaces,

like the space between words, and instructions to start a new line.

And in most high-level languages, you'll probably be using a STRING instead,

Then you've got Boolean, or BOOL, named after George Boole, an English mathematician.

A boolean only contains either a zero or a one. A yes or a no.

Then there's floating-point numbers, or FLOATs.

Floats are complicated and messy and a whole other video, but in short,

they let you store numbers with decimals,

although you might lose a very small bit of precision as you do it.

There are others, other types, in a lot of languages,

I know it's more complicated than this: but this is just the basics.

So. Most languages use “explicit type declaration”.

So when you declare a  when you set up that bucket,

So, x is an integer, it can only hold integers, and right now, that integer is 2.

including some popular ones that people tend to get started with, and that I like,

It just gets figured out from your code. That's called “implicit declaration”.

So in JavaScript, you can just type x = 1.5 and it'll know, that's a number.

Put the 1.5 in quotes, and it'll go, ah, it's a string.

So, okay, it's storing 1.5 and “1.5” as different ones and zeros.

Well, in JavaScript, the plus sign means two different things.

It's the addition operator, for adding two numbers together.

But it's also the concatenation operator, for combining two strings together.

So if x is “1.5”, you ask for x + x... it returns 3.

But if either of those xs is "1.5", a string,

And that's called “type casting”; converting from one data type to another.

Some languages require the programmer to explicitly request the conversion in code.

Other languages, like JavaScript there, do it automatically.

JavaScript is referred to as having “weak typing” as opposed to “strong typing”.

And it's weak because, even if that 1.5 is a string,

Unlike the plus sign, that asterisk can only mean 'multiply',

so it can only handle an integer or a floating-point number.

and it won't throw an error like a strongly-typed language would.

It'll just convert it for you on the fly.

Really convenient. Really easy to program with.

Really easy to accidentally screw things up

and create a bug that'll take you hours to track down.

Or worse, create a bug that you don't even notice until much, much later.

In a lot of languages, you can also cast to and from boolean values.

and experienced programmers who are watching this may already be grimacing.

If you convert an empty string to a boolean,

So you can just test for an empty string with if(x).

you can ask for true + true and it'll tell you that the answer to that is 2,

because when you cast 'true' to a number you get 1.

In PHP, a language notable for many questionable design decisions,

even a string with just a single zero in it will get converted to a boolean false,

there's a special case just for that string.

Which can cause a lot of unexpected bugs.

Now, there is a workaround for that in loosely-typed languages.

Normally, if you want to compare two variables,

You can't use a single one, because that's used for assigning variables.

I've been coding for about thirty years and I still absent-mindedly screw that up sometimes.

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Why TRUE + TRUE = 2: Data Types

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