start simple examples

examples/simple-c/.gitignore

@@ -0,0 +1 @@
+demo

examples/simple-c/Makefile

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+demo: demo.c
+	gcc \
+		-DSQLITE_CORE \
+		-I../../ -I../../vendor \
+		demo.c ../../sqlite-vec.c ../../vendor/sqlite3.c \
+		-o $@

examples/simple-c/demo.c

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+#include "sqlite3.h"
+#include "sqlite-vec.h"
+#include <stdio.h>
+#include <unistd.h>
+#include <assert.h>
+
+int main(int argc, char *argv[]) {
+  int rc = SQLITE_OK;
+  sqlite3 *db;
+  sqlite3_stmt *stmt;
+
+  rc = sqlite3_auto_extension((void (*)())sqlite3_vec_init);
+  assert(rc == SQLITE_OK);
+
+  rc = sqlite3_open(":memory:", &db);
+  assert(rc == SQLITE_OK);
+
+  rc = sqlite3_prepare_v2(db, "SELECT sqlite_version(), vec_version()", -1, &stmt, NULL);
+  assert(rc == SQLITE_OK);
+
+  rc = sqlite3_step(stmt);
+  printf("sqlite_version=%s, vec_version=%s\n", sqlite3_column_text(stmt, 0), sqlite3_column_text(stmt, 1));
+  sqlite3_finalize(stmt);
+
+  rc = sqlite3_prepare_v2(db, "CREATE VIRTUAL TABLE vec_items USING vec0(embedding float[8])", -1, &stmt, NULL);
+  assert(rc == SQLITE_OK);
+  rc = sqlite3_step(stmt);
+  assert(rc == SQLITE_DONE);
+  sqlite3_finalize(stmt);
+
+
+  static const struct {
+    sqlite3_int64 id;
+    float vector[8];
+  } items[] = {
+    {1, {0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8}},
+    {2, {0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8}},
+  };
+
+  rc = sqlite3_exec(db, "BEGIN", NULL, NULL, NULL);
+  assert(rc == SQLITE_OK);
+  rc = sqlite3_prepare_v2(db, "INSERT INTO vec_items(rowid, embedding) VALUES (?, ?)", -1, &stmt, NULL);
+  assert(rc == SQLITE_OK);
+  for (unsigned long i = 0; i < sizeof(items) / sizeof(items[0]); i++) {
+    sqlite3_bind_int64(stmt, 1, items[i].id);
+    sqlite3_bind_blob(stmt, 2, items[i].vector, sizeof(items[i].vector), SQLITE_STATIC);
+    rc = sqlite3_step(stmt);
+    assert(rc == SQLITE_DONE);
+    sqlite3_reset(stmt);
+  }
+  sqlite3_finalize(stmt);
+  rc = sqlite3_exec(db, "COMMIT", NULL, NULL, NULL);
+  assert(rc == SQLITE_OK);
+
+
+  rc = sqlite3_prepare_v2(db,
+    "SELECT "
+    "  rowid, "
+    "  distance "
+    "FROM vec_items "
+    "WHERE embedding MATCH ?1 "
+    "ORDER BY distance "
+    "LIMIT 5 "
+  , -1, &stmt, NULL);
+  assert(rc == SQLITE_OK);
+
+  float query[8] = {0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8};
+  sqlite3_bind_blob(stmt, 1, query, sizeof(query), SQLITE_STATIC);
+
+  while(1) {
+    rc = sqlite3_step(stmt);
+    if(rc == SQLITE_DONE) break;
+    assert(rc==SQLITE_ROW);
+    sqlite3_int64 rowid = sqlite3_column_int64(stmt, 0);
+    double distance = sqlite3_column_double(stmt, 1);
+    printf("rowid=%lld distance=%f\n", rowid, distance);
+  }
+  sqlite3_finalize(stmt);
+  sqlite3_close(db);
+  return 0;
+}