Appendix B: Open Design Questions

Small items not yet pinned to a single answer in the reference.

The original draft’s question list has been mostly settled during implementation. Items that remain open:

Whether unused val bindings produce a warning (currently silent — the compiler does not warn).

Resolved

The following items from the original draft have been resolved by the implementation:

Shape-mismatch traps include source location. Element-wise rank-1 and rank-2 operations trap with a message such as element-wise '+': shape mismatch plus the source position of the operator. Rank-1 length mismatches in dot and similar prelude functions include both lengths.
for x in arr iterates by value. Each loop iteration binds x to a copy of the next element. This matches the value-semantics design of the language and avoids a “borrow that escapes the loop” footgun.
String formatting via f-strings. Scala-style f"..." (sibling of s"...") covers width, precision, alignment, padding, hex / octal / binary conversions, and the %%/$$ escapes — replacing the earlier deferred format() builtin. See spec §10.6.