apl: quick-wins bundle — decimals + ⎕← + strings (+10 tests, 460/460)

Three small unblockers in one iteration:
- tokenizer: read-digits! now consumes optional ".digits" suffix,
  so 3.7 and ¯2.5 are single number tokens.
- tokenizer: ⎕ followed by ← emits a single :name "⎕←" token
  (instead of splitting on the assign glyph).  Parser registers
  ⎕← in apl-quad-fn-names; apl-monadic-fn maps to apl-quad-print.
- eval-ast: :str AST nodes evaluate to char arrays.  Single-char
  strings become rank-0 scalars; multi-char become rank-1 vectors
  of single-char strings.

lib/apl/parser.sx

@@ -82,7 +82,7 @@
     "⍎"
     "⍕"))
 
-(define apl-quad-fn-names (list "⎕FMT"))
+(define apl-quad-fn-names (list "⎕FMT" "⎕←"))
 
 (define
   apl-parse-op-glyph?

lib/apl/tests/pipeline.sx

@@ -178,3 +178,32 @@
   "apl-run \"(⍳5)[3] × 7\" → 21"
   (mkrv (apl-run "(⍳5)[3] × 7"))
   (list 21))
+
+(apl-test "decimal: 3.7 → 3.7" (mkrv (apl-run "3.7")) (list 3.7))
+
+(apl-test "decimal: ¯2.5 → -2.5" (mkrv (apl-run "¯2.5")) (list -2.5))
+
+(apl-test "decimal: 1.5 + 2.5 → 4" (mkrv (apl-run "1.5 + 2.5")) (list 4))
+
+(apl-test "decimal: ⌊3.7 → 3" (mkrv (apl-run "⌊ 3.7")) (list 3))
+
+(apl-test "decimal: ⌈3.7 → 4" (mkrv (apl-run "⌈ 3.7")) (list 4))
+
+(apl-test
+  "⎕← scalar passthrough"
+  (mkrv (apl-run "⎕← 42"))
+  (list 42))
+
+(apl-test
+  "⎕← vector passthrough"
+  (mkrv (apl-run "⎕← 1 2 3"))
+  (list 1 2 3))
+
+(apl-test
+  "string: 'abc' → 3-char vector"
+  (mkrv (apl-run "'abc'"))
+  (list "a" "b" "c"))
+
+(apl-test "string: 'a' is rank-0 scalar" (mksh (apl-run "'a'")) (list))
+
+(apl-test "string: 'hello' shape (5)" (mksh (apl-run "'hello'")) (list 5))

lib/apl/tokenizer.sx

@@ -138,12 +138,22 @@
                  (begin
                    (consume! "¯")
                    (let ((digits (read-digits! "")))
-                     (tok-push! :num (- 0 (parse-int digits 0))))
+                     (if (and (< pos src-len) (= (cur-byte) ".")
+                              (< (+ pos 1) src-len) (apl-digit? (nth source (+ pos 1))))
+                       (begin (advance!)
+                              (let ((frac (read-digits! "")))
+                                (tok-push! :num (- 0 (string->number (str digits "." frac))))))
+                       (tok-push! :num (- 0 (parse-int digits 0)))))
                    (scan!)))
                 ((apl-digit? ch)
                  (begin
                    (let ((digits (read-digits! "")))
-                     (tok-push! :num (parse-int digits 0)))
+                     (if (and (< pos src-len) (= (cur-byte) ".")
+                              (< (+ pos 1) src-len) (apl-digit? (nth source (+ pos 1))))
+                       (begin (advance!)
+                              (let ((frac (read-digits! "")))
+                                (tok-push! :num (string->number (str digits "." frac)))))
+                       (tok-push! :num (parse-int digits 0))))
                    (scan!)))
                 ((= ch "'")
                  (begin
@@ -155,7 +165,9 @@
                  (let ((start pos))
                    (begin
                      (if (cur-sw? "⎕") (consume! "⎕") (advance!))
-                     (read-ident-cont!)
+                     (if (and (< pos src-len) (cur-sw? "←"))
+                       (consume! "←")
+                       (read-ident-cont!))
                      (tok-push! :name (slice source start pos))
                      (scan!))))
                 (true

lib/apl/transpile.sx

@@ -40,6 +40,7 @@
       ((= g "⍋") apl-grade-up)
       ((= g "⍒") apl-grade-down)
       ((= g "⎕FMT") apl-quad-fmt)
+      ((= g "⎕←") apl-quad-print)
       (else (error "no monadic fn for glyph")))))
 
 (define
@@ -97,6 +98,15 @@
       ((tag (first node)))
       (cond
         ((= tag :num) (apl-scalar (nth node 1)))
+        ((= tag :str)
+          (let
+            ((s (nth node 1)))
+            (if
+              (= (len s) 1)
+              (apl-scalar s)
+              (make-array
+                (list (len s))
+                (map (fn (i) (slice s i (+ i 1))) (range 0 (len s)))))))
         ((= tag :vec)
           (let
             ((items (rest node)))