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Eta REPL Semantics

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Overview

eta_repl reads one submission at a time, wraps it as a module, compiles it, and keeps state across submissions.

The REPL supports redefinition by shadowing older bindings for new code.

Profiling Meta-Command

eta_repl supports a one-shot profiler command:

:prof [sample|trace] [--mode sample|trace] [--hz N] [--format FMT]

FMT supports:

Behavior:

  1. :prof ... configures profiling for the next non-command submission.
  2. The next submission executes normally.
  3. The requested profile report is printed after that submission.
  4. The profile request is consumed (one-shot).

Examples:

eta> :prof trace --format pretty
eta> (my-workload)

eta> :prof sample --hz 2000 --format json
eta> (my-workload)

Use :prof off (or :prof disable) to clear a pending profile request.

For full profiling workflow and report interpretation, see Profiling.

Redefinition Rules

  1. If you redefine a name, later submissions use the newest definition.
  2. Older submissions keep the bindings they were compiled with.
  3. Unrelated names from older submissions remain visible until shadowed.

Example:

eta> (defun f (x) x)
eta> (f 10)
=> 10
eta> (defun f (x) (+ x 1))
eta> (f 10)
=> 11

Closure behavior:

eta> (defun f (x) x)
eta> (defun g (x) (f x))
eta> (defun f (x) (* x 2))
eta> (g 5)
=> 5
eta> (f 5)
=> 10

g keeps calling the original f because it was compiled before the redefinition.

Implementation Notes

Each submission is wrapped into an internal module named like __repl_N. When building a new submission, the REPL imports only the currently live names from prior REPL modules. Older shadowed bindings are not imported into new submissions.