# EvalFn

Evaluator that wraps a user-provided function for dynamic evaluation.

This class allows users to create evaluators from any callable function, automatically handling parameter passing, validation, and result conversion to Score objects.

Key Features:

* **Dynamic Function Wrapping**: Converts any callable into an evaluator
* **Argument Validation**: Validates that provided arguments match function signature
* **Smart Result Conversion**: Automatically converts various return types to Score
* **Error Handling**: Gracefully handles function execution and argument errors
* **Parameter Flexibility**: Supports functions with any parameter signature

## Parameters

| Parameter    | Type          | Required | Default | Description                                                                  |
| ------------ | ------------- | -------- | ------- | ---------------------------------------------------------------------------- |
| `fn`         | `Callable`    | ✓        | `-`     | The callable function to wrap as an evaluator.                               |
| `score_name` | `str \| None` | ✗        | `None`  | Optional custom name for the score. If not provided, uses the function name. |

## Example

```python
def equals(a, b):
        return a == b

    evaluator = EvalFn(equals, score_name="exact_match")
    score = evaluator.score(a="hello", b="hello")
    print(score.value)  # 1.0

    def length_check(text, min_length=5):
            return len(text) >= min_length

        evaluator = EvalFn(length_check)

        # Invalid arguments raise TypeError
        try:
                evaluator.score(wrong_param="value")
            except TypeError as e:
                    print(f"Error: {e}")
```

## *property* name *: str*

## score()

Execute the wrapped function and convert result to Score.

Calls the wrapped function with the provided arguments and converts the result to a Score object. Validates that the provided arguments match the function's signature.

### Parameters

| Parameter  | Type  | Required | Default | Description                                                                                                   |
| ---------- | ----- | -------- | ------- | ------------------------------------------------------------------------------------------------------------- |
| `*args`    | `Any` | ✗        | `-`     | Positional arguments to pass to the wrapped function.                                                         |
| `**kwargs` | `Any` | ✗        | `-`     | Keyword arguments to pass to the wrapped function. Only kwargs that match the function's parameters are used. |

### Returns

A Score object representing the function's evaluation result.

**Return type:** Score

### Raises

**TypeError** – If the provided arguments don't match the function signature.

{% hint style="info" %}
The function result is converted to a Score as follows:

* bool: 1.0 for True, 0.0 for False
* int/float: Direct value conversion
* Score: Returns as-is
  {% endhint %}


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