The Epsilon Test

What this C++ code-tracing question tests

This is a hard C++ question that asks you to read and predict the output of a code snippet. It rewards deep familiarity with language semantics, particularly around floating-point representation, numeric limits, and how the standard library handles edge cases in comparisons and arithmetic.

Solving it requires you to step through the code mentally, keeping track of how values are stored and transformed at each stage. Interviewers use questions like this to assess whether you understand the gap between mathematical intuition and actual machine behaviour—a critical skill when debugging performance issues or numerical instability in production systems.

• Floating-point precision and rounding
• Standard library numeric constants and limits
• Comparison semantics for real-valued types
• Order of operations and type conversions