Perplexing keyword behavior in splice

[gilch]

(defn print-args [&rest args &kwargs kwargs]
  (print args kwargs))

=> (print-args :key 42)  ; normal keyword magic
print_args(key=42)
() {'key': 42}
=> (print-args ':key 42)  ; quote to pass keyword as data
from hy import HyKeyword
print_args(HyKeyword('\ufdd0:key'), 42)
('\ufdd0:key', 42) {}

That was strange for a Lisp, but easy enough to understand.

=> (eval `(print-args ~@[:key 42]))  ; raw keyword
from hy.core.language import eval
from hy import HyExpression, HySymbol
eval(HyExpression((([] + [HySymbol('print_args')]) + list(['\ufdd0:key', 42]))))
('\ufdd0:key', 42) {}
=> (eval `(print-args ~@[':key 42]))  ; quoted keyword
from hy.core.language import eval
from hy import HyExpression, HyKeyword, HySymbol
eval(HyExpression((([] + [HySymbol('print_args')]) + list([HyKeyword('\ufdd0:key'), 42]))))
() {'key': 42}

Somehow it became the opposite? Is this how it's supposed to work?

[Kodiologist]

I think so. The trick is that in Hy, unlike most Lisps, keywords don't evaluate to themselves. They evaluate to strings, not HyKeywords. So the expression `(print-args ~@[:key 42]) evaluates to (print-args "\\ufdd0:key" 42); if you evaluate this, the compiler will see the string "\\ufdd0:key" instead of a literal keyword. By contrast, `(print-args ~@[':key 42]) evaluates to (print-args :key 42). If you want to pass a real HyKeyword to print-args here, you need two single quotes (i.e., `(print-args ~@['':key 42])) because you're evaluating :key twice, once with ~@ and once with eval.