search: synonym / query expansion + 9 tests

A synonym map [(Term,[Term])] expands a query term to itself + synonyms
(expandTerm); synDocs unions and synRankTfIdf ranks the expanded set. 214/214.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/search/api.sx

@@ -7,7 +7,7 @@
 ;; topNTfIdfAcl, searchBm25Acl, prefixTerms, prefixDocs, prefixRankTfIdf,
 ;; paginate, pageTfIdf, pageBm25, resultCount, editDist, fuzzyTerms, fuzzyDocs,
 ;; fuzzyRankTfIdf, highlight, snippet, stem, stemText, stemTokens, indexStemmed,
-;; nearDocs.
+;; nearDocs, expandTerm, synDocs, synRankTfIdf.
 
 (define
   search/src
@@ -34,4 +34,6 @@
     "\n"
     search/stem-src
     "\n"
-    search/near-src))
+    search/near-src
+    "\n"
+    search/syn-src))

lib/search/conformance.conf

@@ -30,6 +30,7 @@ PRELOADS=(
   lib/search/highlight.sx
   lib/search/stem.sx
   lib/search/near.sx
+  lib/search/syn.sx
   lib/search/api.sx
   lib/search/testlib.sx
 )
@@ -46,4 +47,5 @@ SUITES=(
   "highlight:lib/search/tests/highlight.sx"
   "stem:lib/search/tests/stem.sx"
   "near:lib/search/tests/near.sx"
+  "syn:lib/search/tests/syn.sx"
 )

lib/search/scoreboard.json

@@ -1,8 +1,8 @@
 {
   "lang": "search",
-  "total_passed": 205,
+  "total_passed": 214,
   "total_failed": 0,
-  "total": 205,
+  "total": 214,
   "suites": [
     {"name":"index","passed":18,"failed":0,"total":18},
     {"name":"boolean","passed":28,"failed":0,"total":28},
@@ -14,7 +14,8 @@
     {"name":"fuzzy","passed":18,"failed":0,"total":18},
     {"name":"highlight","passed":12,"failed":0,"total":12},
     {"name":"stem","passed":18,"failed":0,"total":18},
-    {"name":"near","passed":9,"failed":0,"total":9}
+    {"name":"near","passed":9,"failed":0,"total":9},
+    {"name":"syn","passed":9,"failed":0,"total":9}
   ],
-  "generated": "2026-06-06T23:01:07+00:00"
+  "generated": "2026-06-06T23:25:35+00:00"
 }

lib/search/scoreboard.md

@@ -1,6 +1,6 @@
 # search scoreboard
 
-**205 / 205 passing** (0 failure(s)).
+**214 / 214 passing** (0 failure(s)).
 
 | Suite | Passed | Total | Status |
 |-------|--------|-------|--------|
@@ -15,3 +15,4 @@
 | highlight | 12 | 12 | ok |
 | stem | 18 | 18 | ok |
 | near | 9 | 9 | ok |
+| syn | 9 | 9 | ok |

lib/search/syn.sx

@@ -0,0 +1,10 @@
+;; search synonym / query expansion — Haskell source fragment. Depends on index +
+;; rank. A synonym map is an assoc list [(Term, [Term])]; a query term is expanded
+;; to itself plus its synonyms, then the expanded set is unioned / ranked.
+;;   expandTerm    :: [(Term,[Term])] -> Term -> [Term]
+;;   synDocs       :: [(Term,[Term])] -> Term -> Index -> [DocId]
+;;   synRankTfIdf  :: [(Term,[Term])] -> Term -> Index -> [DocId]
+
+(define
+  search/syn-src
+  "synLookup synmap t = case lookup t synmap of { Nothing -> [] ; Just ss -> ss }\nexpandTerm synmap t = t : synLookup synmap t\nsynDocs synmap t idx = foldl (candStep idx) [] (expandTerm synmap t)\nsynRankTfIdf synmap t idx = rankTfIdf (expandTerm synmap t) idx\n")

lib/search/tests/syn.sx

@@ -0,0 +1,53 @@
+;; Extension — synonym / query expansion.
+;; synmap: car -> automobile, vehicle ; big -> large
+;; Corpus: 1 "fast car"  2 "shiny automobile"  3 "big truck"  4 "large house"  5 "vehicle review"
+
+(define
+  syn-setup
+  "synmap = [(\"car\", [\"automobile\", \"vehicle\"]), (\"big\", [\"large\"])]\nidx = indexDoc 5 \"vehicle review\" (indexDoc 4 \"large house\" (indexDoc 3 \"big truck\" (indexDoc 2 \"shiny automobile\" (indexDoc 1 \"fast car\" emptyIndex))))\n")
+
+(define
+  syn-cases
+  (list
+    (list
+      "expand term with synonyms"
+      "expandTerm synmap \"car\""
+      (list "car" "automobile" "vehicle"))
+    (list
+      "expand single synonym"
+      "expandTerm synmap \"big\""
+      (list "big" "large"))
+    (list "expand unknown term" "expandTerm synmap \"banana\"" (list "banana"))
+    (list
+      "syn docs union"
+      "synDocs synmap \"car\" idx"
+      (list 1 2 5))
+    (list
+      "syn docs single synonym"
+      "synDocs synmap \"big\" idx"
+      (list 3 4))
+    (list
+      "syn docs no synonyms"
+      "synDocs synmap \"house\" idx"
+      (list 4))
+    (list "syn docs absent" "synDocs synmap \"plane\" idx" (list))
+    (list
+      "syn rank expanded"
+      "synRankTfIdf synmap \"car\" idx"
+      (list 1 2 5))
+    (list
+      "syn rank single"
+      "synRankTfIdf synmap \"big\" idx"
+      (list 3 4))))
+
+(define
+  syn-results
+  (search-batch syn-setup (map (fn (c) (nth c 1)) syn-cases)))
+
+(map-indexed
+  (fn
+    (i c)
+    (hk-test (nth c 0) (nth syn-results i) (nth c 2)))
+  syn-cases)
+
+{:fail hk-test-fail :pass hk-test-pass :fails hk-test-fails}

plans/search-on-sx.md

@@ -119,9 +119,13 @@ lib/search/index.sx                     lib/search/eval.sx
 - [x] stemming (suffix stripping) — `stem`, `stemText`, `stemTokens`, `indexStemmed`
   — 18 tests
 - [x] proximity / NEAR — `nearDocs k t1 t2` (unordered, within k positions) — 9 tests
+- [x] synonym / query expansion — `expandTerm`, `synDocs`, `synRankTfIdf` — 9 tests
 
 ## Progress log
 
+- **Extension: synonyms/query expansion (214/214 total).** A synonym map
+  `[(Term,[Term])]` expands a query term to itself + synonyms (`expandTerm`); `synDocs`
+  unions, `synRankTfIdf` ranks the expanded set. 9 tests.
 - **Extension: proximity/NEAR (205/205 total).** `nearDocs k t1 t2 idx` returns docs
   where both terms occur within k positions (unordered), candidates = posting
   intersection, filtered on the positional postings. 9 tests.