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4.4 REPL limitations

Making Hoot a fully live hackable environment is a work in progress. Developers that are already used to the Guile development experience will find some features missing.

Some notable limitations are:

• Not all code that can be compiled to Wasm can be evaluated in the Scheme interpreter at runtime. For example, modules that include define-foreign expressions (see Foreign function interface) cannot be interpreted because they generate inline Wasm code that requires the compiler. To use such modules, they must be compiled into the Wasm binary of the program being developed. As a consequence, adding new FFI bindings requires recompiling and restarting the program. To ensure that the desired module is compiled into a development build, import it from one or more other modules or import it in the top-level program.
• Re-evaluating a define-module form does not propagate new exports into modules that have imported it like it does in Guile. To use the new exported symbols, the dependent module must have its define-module form re-evaluated. If the module is instead being used from the REPL then it must be re-imported with the ,use meta-command (see REPL meta-commands).
• Guile’s module reflection API is not implemented.
• Many of Guile’s meta-commands are missing, including most of the debugging tools.
• There are no $1, $2, … history variables at the REPL.