73 lines
1.6 KiB
Markdown
73 lines
1.6 KiB
Markdown
|
# The compiler
|
||
|
|
|
||
|
|
The compiler is the program that takes your THP code and converts it
|
||
|
|
into something that the computer can run (in this case, PHP code).
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
The compiler reads your code and tries to understand it.
|
||
|
|
When it can't understand some part, it will ask you to clarify what
|
||
|
|
you meant, with an error.
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
## Compile time vs runtime
|
||
|
|
|
||
|
|
Compile time is when you build your program.
|
||
|
|
|
||
|
|
Runtime is when you run your program.
|
||
|
|
|
||
|
|
To make an analogy with cars, compile time would be the factory,
|
||
|
|
while runtime would be using the finished car.
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
The compiler is very strict. If it finds any errors during compile time
|
||
|
|
it will refuse to build the program.
|
||
|
|
|
||
|
|
|
||
|
|
### Compile time errors
|
||
|
|
|
||
|
|
Compile time errors are errors that happen while the compiler is
|
||
|
|
building your program. In the car analogy, a compile error would happen
|
||
|
|
if there's an error in the "blueprint"
|
||
|
|
|
||
|
|
|
||
|
|
### Runtime errors
|
||
|
|
|
||
|
|
These are errors that happen to the built program, or in this case,
|
||
|
|
the finished car. It would be like the car blowing up while on the highway.
|
||
|
|
|
||
|
|
To minimize the amount of runtime errors the compiler tries to catch them all
|
||
|
|
during compile time. It's better if it fails in the factory than in the
|
||
|
|
real world.
|
||
|
|
|
||
|
|
|
||
|
|
## The compiler and datatypes
|
||
|
|
|
||
|
|
The first measure the compiler takes is to check that all the datatypes
|
||
|
|
match. If an operation requires a number, you can't just give it a string.
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
For example, if we wanted to add a number to a string, we would get an
|
||
|
|
error:
|
||
|
|
|
||
|
|
```thp
|
||
|
|
50 + "hello" // Error: The `+` operator expects two Numbers,
|
||
|
|
// but an String was found.
|
||
|
|
```
|
||
|
|
|
||
|
|
This way, we can assure that many errors are avoided (since it doesn't
|
||
|
|
really make sense to add a number to a text).
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|
||
|
|
|