stanfordnlp/CoreNLP · error · IllegalArgumentException

arguments expected, got

Error message

${nargs} arguments expected, got ${in.size()}

What it means

ValueFunctions.NumericFunction.apply validates argument count before computing: if the function declares a fixed nargs > 0 and the incoming list size differs, it throws this IllegalArgumentException. It enforces arity for numeric functions (e.g. MIN/MAX with fixed argument counts) in TokensRegex expressions.

Solutions

1. Count the function's required arguments and supply exactly nargs values in the call.
2. Log/inspect in.size() from the exception message to see how many were actually passed and where the extras/missing ones come from.
3. If arguments come from capture groups, guard with a count check before invoking the function.
4. Use a variadic function (nargs == -1 / nargs <= 0 path) if a variable argument count is intended.

Example fix

// before
MIN()               // 0 args, function requires 2
// after
MIN($left, $right)  // matches nargs == 2

if (args.size() != expectedNargs) {
  throw new IllegalStateException("MIN/MAX function needs " + expectedNargs + " args, got " + args.size());
}

static boolean hasArity(java.util.List<?> in, int nargs) {
  return nargs <= 0 || in.size() == nargs;
}

try { Value v = func.apply(env, in); }
catch (IllegalArgumentException ex) {
  if (ex.getMessage().contains("arguments expected, got")) {
    log.error("Arity mismatch calling numeric function: " + ex.getMessage());
  }
  throw ex;
}

When it happens

Trigger: Calling a TokensRegex numeric function (e.g. in a rule's action or expression) with the wrong number of arguments — too few from missing bindings, too many from extra comma-separated expressions; binding list built programmatically with wrong size.

Common situations: Rule expressions like FUNC{...} where the expected fixed arity doesn't match; captured-groups list feeding a numeric function with a variable count; miscounted arguments after editing a rule.

Understand the failure class

Background: "missing required argument" and "the following required arguments were not provided": what required-argument errors mean and how to fix them — this error's family across 20 libraries.

Related errors

• 2 arguments expected, got
• Invalid number of arguments to
• Annotation field cannot be null
• : Entry has multiple types for : . Taking type to be
• Attribute already defined:

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/97f9155aa8676261. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/ling/tokensregex/types/ValueFunctions.java:184

    public abstract Number compute(Number...ns);

    @Override
    public boolean checkArgs(List<Value> in) {
      if (nargs > 0 && in.size() != nargs) {
        return false;
      }
      for (Value v : in) {
        if (v == null || !(v.get() instanceof Number)) {
          return false;
        }
      }
      return true;
    }

    @Override
    public Value apply(Env env, List<Value> in) {
      if (nargs > 0 && in.size() != nargs) {
        throw new IllegalArgumentException(nargs + " arguments expected, got " + in.size());
      }
      Number[] numbers = new Number[in.size()];
      for (int i = 0; i < in.size(); i++) {
        numbers[i] = (Number) in.get(i).get();
      }
      Number res = compute(numbers);
      return new Expressions.PrimitiveValue(resultTypeName, res);
    }
  }

  public static final ValueFunction ADD_FUNCTION = new NumericFunction("ADD", 2) {
    @Override
    public Number compute(Number... in) {
      if (isInteger(in[0]) && isInteger(in[1])) {
        return in[0].longValue() + in[1].longValue();
      } else {
        return in[0].doubleValue() + in[1].doubleValue();
      }

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