Embedded commands

Embedded commands are FatScript's low-level functions that can be invoked with keywords preceded by a dollar sign $. These commands are always available, implemented as compiled code, and require no imports.

Unlike methods, they take no explicit arguments, but may read from specific entry names in the current scope, or even from the interpreter's internal state.

Handy ones

Here a are some embedded commands that could be useful to know:

  • $break pauses execution and loads the debugging console
  • $debug toggles interpreter debug logs
  • $exit exits program with provided code
  • $keepDotFry keeps the config (.fryrc) in scope after startup
  • $result toggles result printing at the end of execution
  • $root provides a reference to global scope
  • $self provides a self reference to method/instance scope
  • $bytesUsage returns total of bytes allocated at the moment
  • $nodesUsage returns total of nodes allocated at the moment
  • $isMain checks if code is executing as main or module

root and self keywords are automatically lifted into $root and $self

You can call those directly on your code, like:

$exit  # terminates the program

in order to use other embedded commands you have to study the C implementation of fry, as the complete list is not documented, refer to embedded.c file

Libs under the hood

Standard libraries wrap embedded calls into methods, providing a more ergonomic interface. You don't need to create an execution scope or load arguments into that scope before delegating execution to them.

For example, here's how you can use the floor method from math lib:

_ <- fat.math

This method is implemented as:

floor = (x: Number): Number -> $floor

Under the hood, the floor method creates an execution scope and loads an argument as x into it. The method then delegates execution to the $floor embedded command, which reads the value of x from the current scope and returns the floor of that number.

You can achieve the same outcome as above method by doing the following:

x = 2.53
$floor  # reads value of x from current scope


You can see which embedded command a library method is calling by looking into the library's implementation via the readLib method from the SDK lib. Technically, there is nothing preventing you from calling embedded commands directly.

For example, you could terminate your program by calling $exit directly, which will exit with code 0 (default) or, if a numeric entry named code exists in the current scope, the value of that entry will be used as the exit code. However, it would be more elegant to import the fat.system library and call the exit method with the desired exit code:

sys <- fat.system
sys.exit(0)  # exits with code 0

This approach makes your code more readable and less prone to errors, and it also provides a better separation of concerns.

It's important to keep in mind that embedded commands are black boxes and not intended for writing common FatScript code. In most cases, you would need to read the underlying C implementation to better grasp what a command is actually doing.

While it's possible to use embedded commands to gain additional runtime performance by avoiding imports and method calls, this is not recommended due to the loss of code readability. In general, it's better to use the standard libraries and follow best practices for writing clear, maintainable code.

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