tcl: Phase 1 parser — word-simple? + word-literal helpers (+15 tests, 67 total)

lib/tcl/parser.sx

@@ -0,0 +1,41 @@
+; Tcl parser — thin layer over tcl-tokenize
+; Adds tcl-parse entry point and word utility fns
+
+; Entry point: parse Tcl source to a list of commands.
+; Returns same structure as tcl-tokenize.
+(define tcl-parse (fn (src) (tcl-tokenize src)))
+
+; True if word has no substitutions — value can be read statically.
+; braced words are always simple. compound words are simple when all
+; parts are plain text with no var/cmd parts.
+(define tcl-word-simple?
+  (fn (word)
+    (cond
+      ((= (get word :type) "braced") true)
+      ((= (get word :type) "compound")
+        (let ((parts (get word :parts)))
+          (every? (fn (p) (= (get p :type) "text")) parts)))
+      (else false))))
+
+; Concatenate text parts of a simple word into a single string.
+; For braced words returns :value directly.
+; For compound words with only text parts, joins them.
+; Returns nil for words with substitutions.
+(define tcl-word-literal
+  (fn (word)
+    (cond
+      ((= (get word :type) "braced") (get word :value))
+      ((= (get word :type) "compound")
+        (if (tcl-word-simple? word)
+          (join "" (map (fn (p) (get p :value)) (get word :parts)))
+          nil))
+      (else nil))))
+
+; Number of words in a parsed command.
+(define tcl-cmd-len
+  (fn (cmd) (len (get cmd :words))))
+
+; Nth word literal from a command (index 0 = command name).
+; Returns nil if word has substitutions.
+(define tcl-nth-literal
+  (fn (cmd n) (tcl-word-literal (nth (get cmd :words) n))))