Description

The Readers.h library is a single-header C++ utility library that provides a compact, consistent collection of console input helpers. Packaged under the readers namespace, the library exposes strongly-typed, template-based functions for reading and validating numeric input, plus helpers for words, lines, single characters, and booleans. It focuses on defensive stream handling, input re-prompting, and simple, reusable API surface for CLI apps and small tools.

Technologies Used

  • Language: C++ (ISO C++)
  • Standard Library headers: <iostream>, <string>
  • Design patterns / concepts: templates, function overloading, default parameters, namespace-based encapsulation

Functionality / Features

  • Generic numeric readers: readNumber<T>(msg), range-checked overload readNumber<T>(msg, from, to). Works for any numeric type T (e.g., int, long, double).
  • Specialized numeric constraints: readPositiveNumber, readNegativeNumber, readNonPositiveNumber, readNonNegativeNumber, readNonZeroNumber — each enforces the expected sign/constraint.
  • String & word input: readWord(msg) for whitespace-delimited tokens, and readString(msg, isAfterCin) which correctly handles getline after cin.
  • Character input with whitelist: readCharacter(msg, allowedChars, errMsg) only accepts characters included in the allowedChars string (useful for Y/N prompts or single-key menus).
  • Boolean helper: readBoolean(msg) — wraps readCharacter and returns true/false for y/n responses (case-insensitive).
  • Robust stream handling: All readers clear cin on failure, ignore remaining input up to numeric_limits<streamsize>::max(), and loop until valid input is provided.
  • Developer ergonomics: Optional errMsg parameter lets the function change the prompt text after the first invalid attempt.

Implementation Highlights

  • Template-first design
    • Numeric functions are templates, making the API flexible across integer and floating types without duplication.
    • Range-checked overload uses the same function name with different signatures for intuitive use.
  • Careful cin recovery
    • After invalid input the functions call cin.clear() and cin.ignore(numeric_limits<streamsize>::max(), '\n') to remove the bad token and any leftover input so subsequent reads are clean.
    • cin.peek() != '\n' is used to detect trailing input on the same line (helps avoid accepting 12abc as 12).
  • Consistent UX
    • Each function accepts a prompt string and an optional alternate error prompt to guide users after the first failed attempt.
    • readString supports the common getline-after-cin pattern using cin >> ws when isAfterCin is true.
  • Composable building blocks
    • Higher-level helpers wrap lower-level ones (e.g., readBoolean uses readCharacter), reducing duplication and keeping logic centralized.
  • Single-header convenience
    • Being header-only makes it drop-in for small projects and educational codebases; templates are defined inline so no linking concerns.

Conclusion

  • This project demonstrates attention to the small but critical details of user input and defensive programming — a quality every production CLI or tooling project needs.
  • Shows practical knowledge of templates, overloading, stream state management, and API ergonomics.
  • A neat, reusable utility that’s immediately useful in other projects — great to cite during interviews as an example of improving developer experience and input reliability.

How to Use

  1. Download the header file from the section below.
  2. Include it in your C++ project using #include "...", with the appropriate path between the double quotes.

Source Code

You can find the source code for this header here.

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