From ae2842cc07663fd07404f480f01e9196c7ccc673 Mon Sep 17 00:00:00 2001
From: Marshall Lochbaum <mwlochbaum@gmail.com>
Date: Thu, 12 Aug 2021 19:33:54 -0400
Subject: Check for correct special name use in headers

---
 src/c.bqn | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

(limited to 'src')

diff --git a/src/c.bqn b/src/c.bqn
index f8f3b5a9..f0fde947 100644
--- a/src/c.bqn
+++ b/src/c.bqn
@@ -174,13 +174,14 @@ Parse ← {r‿vn‿i‿e‿def←𝕨⋄nv←≠vn
   "Missing operand in header"_err_(/HF) ho∧hc∨hd
   hm←¬ho∨ha←ho<(0=hr)∧1=hn                  # Mask for main name; header arguments
   "Invalid header structure"_err_(hm//∘HF) 1⊸»⊸=hm/hc
+  hv←(ha×1+«hc)+(ho×4+«3=hr)+hm×3×1-˜2⌊hr
+  "Incorrect special name"_err_(/HF) (M⟜bI>(hv+⊑bI)⊸=)hf/𝕩
   hm>↩hc⋄hr/˜↩hm⋄hx←(1»hc)/ha               # Header-derived role hr and immediacy ¬hx
   cw←(hc/»hl∨ha)⌾(ch⊸/)1+-⟜«(»ch)<1(⊢<«)cf  # Body 𝕨: 0 no, 1 allowed, 2 required
-  hl/˜↩hm⋄hm↩hm⌾(hf⊸/)hf
+  hl/˜↩hm
   "Header left argument without right"_err_(/HF) ha>hc+`⊸⊏hx∾0
   hx∨↩1=hr
-  hid←vi‿nv M˜ ht←hm/𝕩
-  "Header operation must be name or valid self-reference (𝕊 or 𝕣)"_err_(/HM) hid<ht≠(⊑bI)+3×1-˜2⌊hr
+  "Header operation must be a single name"_err_(/HF) hm>(hf/𝕩)M bI+0‿nv
   "Only special name inputs allowed in headers for now!"_err_((HO∨HA)//∘HF) ¬bI M˜(ho∨ha)/hf/𝕩
   hu←(𝕩 M bI)<hf∧0<rr
 
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