The slc command

slc --version
slc run [--fuel N] [--interpret] <file.sl> [arg]…
slc compile [-o <file>] [--fuel N] <file.sl>
slc check <file.sl>…
slc fmt [--check | --stdout] <file.sl>…

slc --version prints slc and the package version.

run

slc run checks the file and then runs it. Flags are recognized only before the file. Everything after the file is a word the program reads through args::arguments, including a word that looks like a flag.

With no --interpret, slc compiles to a native executable, links it with the runtime, and executes it. That executable is an x86-64 ELF. On any other host, slc run uses the interpreter, and slc compile stops before linking. --interpret evaluates the checked program on the abstract machine. book/check.sh runs the tutorial programs with --interpret.

--fuel N stops after N steps. Omitting --fuel bounds a run by memory. --fuel 0 runs no SLC code. The integer sent to exit is the process status when it fits in a byte. A status outside 0..=255 fails the process.

A file with a main of the wrong shape is refused before it runs. The required shape is a root proc with no value parameters and one continuation, the status.

compile

slc compile checks the file, links the native executable, and writes that file. It does not run the program.

-o names the executable. --output is the same flag. With neither, the name is the source stem in the current directory, so examples/basics/hello.sl becomes ./hello. The output path has to be a different file from the source.

--fuel N is the executable's step bound, the same bound slc run --fuel N uses. With no --fuel, the executable is bounded by memory. Every argument of the executable is a program argument.

slc compile -o hello examples/basics/hello.sl
./hello

A file with no main, or a main of the wrong shape, is refused and no executable is written.

check

slc check applies the compiler phases and stops. It evaluates nothing, so a program that would not terminate can still be checked. Each diagnostic is prefixed with its file. One failing file fails the command. A file with no main is a library and checks. A glob such as examples/basics/*.sl is the shell's, and examples/errors/ is left out of it because those files fail on purpose.

fmt

slc fmt rewrites each file in place. The layout is four-space indentation, lines within 100 columns, a semicolon after every statement except a block's last expression, and a comma after every arm. A list between braces keeps the line break its author gave it while it fits. A chain breaks before each | when it does not fit. Comments and blank lines are kept.

The formatter changes whitespace and the separators the grammar leaves optional. It refuses to write a file whose formatted text is not the same program. --check writes nothing and fails when a file would change. --stdout prints the result. --check and --stdout together are refused.

Building

From the repository:

cargo build
cargo test
cargo run -- run examples/basics/hello.sl
cargo run -- fmt --check examples/basics/*.sl

cargo test includes the example outputs, the design programs, and a check that SLC sources are formatted. The Emacs mode is editors/emacs/slc-mode.el. C-c C-f formats the buffer through slc fmt.