// rules are t3(text, comment, ruleID)
static GazelleEvalContext gazelle_stdEvalContext(L<T3<S>> rules) {
  long startTime = sysNow();
  new GazelleEvalContext ctx;
  ctx.engine = new RuleEngine2;
  ctx.engine.addRules2(rules);
  gazelle_changeInTypesForRulesWithMultipleInputs(ctx.engine);

  // gather data for predictor
  MultiMap<S> statementsByRule = ai_gazelle_indexStatementsByRule(dm_gazelle_statementsFromAppliedRules());
  ctx.dataByRule = mapValues ai_gazelle_analyzeStatementsForRule(multiMapToMap(statementsByRule));
  
  ctx.predictor = dm_gazelle_standardPredictor();
  done2(startTime, "Making engine with " + n2(rules, "rule"));
  ret ctx;
}

Began life as a copy of #1021523