Formatting numbers for display is a common task in Rust programming. Whether you're building command-line tools, generating reports, or creating user interfaces, you'll need to convert numeric values into human-readable strings with specific formatting requirements.

Rust's format! macro and the std::fmt module provide powerful formatting capabilities. You can control padding, alignment, precision for floating-point numbers, and display integers in different bases (binary, octal, hexadecimal). Understanding format specifiers like {:05}, {:.2}, {:#x}, and {:>10} is essential for producing well-formatted output.

The formatting traits (Display, Binary, Octal, LowerHex, UpperHex) work together with format specifiers to give you complete control over how numbers appear in strings.

Implement the following functions that demonstrate various number formatting techniques:

1. format_padded - Format an integer with leading zeros

   • Takes an i32 and a width usize
   • Returns a String with the number padded to the specified width with leading zeros
   • Negative numbers should include the minus sign before the zeros

2. format_aligned - Format a number with right alignment

   • Takes an i32 and a width usize
   • Returns a String with the number right-aligned in a field of the given width
   • Pad with spaces on the left

3. format_binary - Format an unsigned integer as binary

   • Takes a u32 and returns a String in binary format
   • Should NOT include "0b" prefix

4. format_binary_prefixed - Format an unsigned integer as binary with prefix

   • Takes a u32 and returns a String in binary format
   • Should include "0b" prefix

5. format_hex_lower - Format an unsigned integer as lowercase hexadecimal

   • Takes a u32 and returns a String in lowercase hex format
   • Should NOT include "0x" prefix

6. format_hex_upper_prefixed - Format an unsigned integer as uppercase hex with prefix

   • Takes a u32 and returns a String in uppercase hex format
   • Should include "0x" prefix

7. format_octal - Format an unsigned integer as octal

   • Takes a u32 and returns a String in octal format
   • Should NOT include "0o" prefix

8. format_float_precision - Format a floating-point number with fixed decimal places

   • Takes an f64 and a precision usize
   • Returns a String with exactly the specified number of decimal places

9. format_scientific - Format a floating-point number in scientific notation

   • Takes an f64 and returns a String in lowercase scientific notation (e.g., "1.23e4")

10. format_currency - Format a floating-point number as currency

    • Takes an f64 representing dollars
    • Returns a String in the format "$X.XX" with exactly 2 decimal places
    • Negative amounts should display as "-$X.XX"

use number_formatting::*;
 
// Padding with zeros
assert_eq!(format_padded(42, 5), "00042");
assert_eq!(format_padded(-7, 4), "-007");
// Wider than width
assert_eq!(format_padded(123, 2), "123");
 
// Right alignment
assert_eq!(format_aligned(42, 5), "   42");
assert_eq!(format_aligned(-7, 5), "   -7");
 
// Binary formatting
assert_eq!(format_binary(10), "1010");
assert_eq!(format_binary(255), "11111111");
assert_eq!(format_binary_prefixed(10), "0b1010");
 
// Hexadecimal formatting
assert_eq!(format_hex_lower(255), "ff");
assert_eq!(format_hex_upper_prefixed(255), "0xFF");
 
// Octal formatting
assert_eq!(format_octal(8), "10");
assert_eq!(format_octal(63), "77");
 
// Float precision
assert_eq!(format_float_precision(3.14159, 2), "3.14");
assert_eq!(format_float_precision(2.5, 4), "2.5000");
 
// Scientific notation
assert_eq!(format_scientific(1234.5), "1.2345e3");
assert_eq!(format_scientific(0.00123), "1.23e-3");
 
// Currency formatting
assert_eq!(format_currency(19.99), "$19.99");
assert_eq!(format_currency(-5.5), "-$5.50");
assert_eq!(format_currency(1000.0), "$1000.00");