REPL and Script Mode

REPL and Script Mode#

C2PO has an interactive command shell (REPL) and a script mode that executes the same commands from a file. Both modes use the command system documented in commands, including command arguments and --help on each command.

Starting the REPL#

Run:

python3 c2po.py --interactive

The prompt is c2po>. Internally, the REPL keeps a current program and context, and each command updates that state (for example, parse_c2po loads a program, and type_check annotates it).

If ~/.c2porc exists, C2PO executes it before starting the prompt. This is useful for startup defaults such as debug/logging configuration.

Core REPL Capabilities#

  • Run any registered C2PO command (e.g., help, parse_c2po, type_check, compile, assemble)

  • Use normal command options and flags (e.g., assemble --print out.bin)

  • Get command-specific help (e.g., compile --help)

  • Save/restore state with push and pop

  • Exit with exit (or Ctrl-D / quit from the interactive console)

If a command cannot run because prerequisites are missing (guard conditions), C2PO prints an error and suggests commands that can satisfy the missing condition.

Script Files#

Run a script file with:

python3 c2po.py --script path/to/script.cmd

A script file is plain text with one REPL command per line. Lines are parsed with shell-style quoting, so quoted paths and string arguments are supported.

Small example:

# Parse and compile
parse_c2po specs/example.c2po
parse_map specs/example.map
type_check
desugar
optimize_rewrites
optimize_cse
remove_extended_operators
multi_operators_to_binary
assemble --print build/spec.bin

Script Behavior Notes#

  • Empty lines and lines starting with # are ignored.

  • Commands are executed in order, sharing one REPL state.

  • By default, relative paths are resolved from the script file’s directory.

  • push/pop are valid in scripts and can checkpoint/restore state.

  • exit ends execution early.

Example with state checkpointing:

parse_c2po specs/example.c2po
type_check
push
optimize_rewrites
print_prefix
pop
compile out/spec.bin

In this example, print_prefix runs on the rewritten program, while the final compile runs after restoring the pre-rewrite state.