PSIL

a simple lisp interpreter

How to compile

Should be a regular cmake build, something like

cmake -B build -DCMAKE_BUILD_TYPE=Debug -DSANITIZE=YES
cmake --build build  --parallel $(nproc)

should be enough (you can also change the build type for Release and disable sanitize in case it's too slow)

Pro-tip: all these snippets can be conveniently run from an IDE if it supports it (at least clion does)

How to run tests

Unit tests (assuming build in build):

ctest --test-dir build --verbose --parallel $(nproc)

CLI tests (also assuming build in build and being in repo root):

PSIL="../build/src/psil" clitests/testall.sh

How to use

You can just run the executable and you'll be in REPL mode (ctrl-c to exit should work), or specify an input file like -f <file>, the effect is the same as if you had put it there yourself.

When reading from a file, REPL is still enabled by default and can be disabled with --repl-

Options

You can also change some of the behaviours of the interpreter:

--cell_limit:limit (for example --cell_limit:10000) - limit the amount of cells that can be used

--command_strs[+/-] (for example --command_strs+) - use string representation of commands, useful for debugging the compiler with verbose logging

--default_log_level:level (for example --default_log_level:3) - change the default logging level

--repl[+/-] (for example --repl-) - enable/disable repl

--gc_threshold:threshold (for example --gc_threshold:70) - percentage of cell_limit at which concurrent gc is triggered

Log options

Log can be configured in format of --log:TAG:LEVEL (for example --log:VM:3)

Where level is a number from 0 to 4 (0 - no logs, 4 - most logs)

Possible values for tags are:

MemoryContext - at level 2 it will print GC stats for each run, level 3 a little more stats, level 4 is debugging mode

Compiler - level 3 will print the compilation result of everything evaluated, you also probably want to have --command_strs+ enabled with it

VM - level 3 will print function application and return info, level 4 is debugging mode which will print every instruction and the machine state before/after

Some cooler examples

See the GC in action:

build/src/psil -f clitests/fib.psil --repl- --log:Compiler:3 --command_strs+ --cell_limit:10000 --gc_threshold:10 --log:MemoryContext:2

See a tree of function applications:

build/src/psil -f clitests/coffee.psil --repl- --log:Compiler:3 --command_strs+ --log:VM:3

Super debug mode:

build/src/psil -f clitests/decorate.psil --repl- --command_strs+ --default_log_level:4 --log:MemoryContext:3