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Update getting-started and why for open source release

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Arseny Kapoulkine 2021-10-29 12:56:35 -07:00
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docs/_pages/getting-started.md
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@ -4,25 +4,11 @@ title: Getting Started
toc: true toc: true
--- ---
To get started with Luau you need to install Roblox Studio, which you can download [here](https://www.roblox.com/create). To get started with Luau you need to use `luau` command line binary to run your code and `luau-analyze` to run static analysis (including type checking and linting). You can download these from [Artifacts on a recent build](https://github.com/Roblox/luau/actions/workflows/release.yml).
## Creating a place
If you just want to experiment with the language itself, you can create a simple baseplate game.
<figure>
<img src="{{ site.url }}{{ site.baseurl }}/assets/images/create-new-place.png">
</figure>
## Creating a script ## Creating a script
To create your own testing script, go to ServerScriptService in the explorer tree and add a Script object. To create your own testing script, create a new file with `.lua` as the extension:
<figure>
<img src="{{ site.url }}{{ site.baseurl }}/assets/images/create-script.png">
</figure>
Double-click on the script object and paste this:
```lua ```lua
function ispositive(x) function ispositive(x)
@ -40,7 +26,9 @@ print(isfoo("bar"))
print(isfoo(1)) print(isfoo(1))
``` ```
Note that there are no warnings about calling ``ispositive()`` with a string, or calling ``isfoo()`` a number. You can now run the file using `luau test.lua` and analyze it using `luau-analyze test.lua`.
Note that there are no warnings about calling ``ispositive()`` with a string, or calling ``isfoo()`` a number. This is because the type checking uses non-strict mode by default, which is lenient in how it infers types used by the program.
## Type inference ## Type inference
@ -55,25 +43,18 @@ end
print(ispositive(1)) print(ispositive(1))
print(ispositive("2")) print(ispositive("2"))
function isfoo(a)
return a == "foo"
end
print(isfoo("bar"))
print(isfoo(1))
``` ```
In ``strict`` mode, Luau will infer types based on analysis of the code flow. There is also ``nonstrict`` mode, where analysis is more conservative and types are more frequently inferred as ``any`` to reduce cases where legitimate code is flagged with warnings. In ``strict`` mode, Luau will infer types based on analysis of the code flow. There is also ``nonstrict`` mode, where analysis is more conservative and types are more frequently inferred as ``any`` to reduce cases where legitimate code is flagged with warnings.
In this case, Luau will use the ``return x > 0`` statement to infer that ``ispositive()`` is a function taking an integer and returning a boolean. Similarly, it will use the ``return a == "foo"`` statement to infer that ``isfoo()`` is a function taking a string and returning a boolean. Note that in both cases, it was not necessary to add any explicit type annotations. In this case, Luau will use the ``return x > 0`` statement to infer that ``ispositive()`` is a function taking a number and returning a boolean. Note that in this case, it was not necessary to add any explicit type annotations.
Based on Luau's type inference, the editor now highlights the incorrect calls to ``ispositive()`` and ``isfoo()``: Based on Luau's type inference, the analysis tool will now flag the incorrect call to ``ispositive()``:
<figure> ```
<img src="{{ site.url }}{{ site.baseurl }}/assets/images/error-ispositive.png"> $ luau-analyze test.lua
<img src="{{ site.url }}{{ site.baseurl }}/assets/images/error-isfoo.png"> test.lua(7,18): TypeError: Type 'string' could not be converted into 'number'
</figure> ```
## Annotations ## Annotations
@ -110,9 +91,11 @@ result = ispositive(1)
Oops -- we're returning string values, but we forgot to update the function return type. Since we've told Luau that ``ispositive()`` returns a boolean (and that's how we're using it), the call site isn't flagged as an error. But because the annotation doesn't match our code, we get a warning in the function body itself: Oops -- we're returning string values, but we forgot to update the function return type. Since we've told Luau that ``ispositive()`` returns a boolean (and that's how we're using it), the call site isn't flagged as an error. But because the annotation doesn't match our code, we get a warning in the function body itself:
<figure> ```
<img src="{{ site.url }}{{ site.baseurl }}/assets/images/error-ispositive-string.png"> $ luau-analyze test.lua
</figure> test.lua(5,9): TypeError: Type 'string' could not be converted into 'boolean'
test.lua(7,9): TypeError: Type 'string' could not be converted into 'boolean'
```
The fix is simple; just change the annotation to declare the return type as a string: The fix is simple; just change the annotation to declare the return type as a string:
@ -133,9 +116,10 @@ result = ispositive(1)
Well, almost - since we declared ``result`` as a boolean, the call site is now flagged: Well, almost - since we declared ``result`` as a boolean, the call site is now flagged:
<figure> ```
<img src="{{ site.url }}{{ site.baseurl }}/assets/images/error-ispositive-boolean.png"> $ luau-analyze test.lua
</figure> test.lua(12,10): TypeError: Type 'string' could not be converted into 'boolean'
```
If we update the type of the local variable, everything is good. Note that we could also just let Luau infer the type of ``result`` by changing it to the single line version ``local result = ispositive(1)``. If we update the type of the local variable, everything is good. Note that we could also just let Luau infer the type of ``result`` by changing it to the single line version ``local result = ispositive(1)``.

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docs/_pages/why.md
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@ -24,7 +24,3 @@ As for the runtime, we had to rewrite the interpreter from scratch to get substa
The garbage collector and the core libraries represent more of an incremental change, where we used Lua 5.1 as a baseline but we're continuing to rewrite these as well with performance in mind. The garbage collector and the core libraries represent more of an incremental change, where we used Lua 5.1 as a baseline but we're continuing to rewrite these as well with performance in mind.
While Luau doesn't currently implement JIT/AOT, this is likely to happen at some point; beyond the usual implementation challenges and security concerns, one significant limitation is that we don't have access to JIT on many platforms so for us maintaining excellent interpreted performance for gameplay and application code is more important than reaching peak FLOPS on numerical code. While Luau doesn't currently implement JIT/AOT, this is likely to happen at some point; beyond the usual implementation challenges and security concerns, one significant limitation is that we don't have access to JIT on many platforms so for us maintaining excellent interpreted performance for gameplay and application code is more important than reaching peak FLOPS on numerical code.
## Open source?
Please note that at this time we are not ready to make Luau implementation publicly available in the source form. Right now the only interface to Luau is the Roblox engine (exposed in Roblox game client/server and Roblox Studio).