Hard Tanh

Problem Statement

Implement the "Hard Tanh" function which clamps values to a range.

Background

Hard Tanh is a computationally cheaper approximation of the tanh function:

• Returns $-1$ if $x < -1$
• Returns $1$ if $x > 1$
• Returns $x$ if $-1 \leq x \leq 1$

It's essentially a piecewise linear function that clips values outside [-1, 1].

Your Task

Write a function hard_tanh(values) that applies Hard Tanh element-wise to a list.

Output Format

Return a list of floats with Hard Tanh applied. Round each value to 4 decimal places.