Support scanning an integer from a string with various configuration options

[jwodder]

Add a struct with a scan<T: StrToInt>(&self, s: &str) -> Result<(T, &str), Error> method that parses an integer from the initial portion of s and returns the integer & the remainder of s

• The following options can be set as fields of the struct (possibly via a builder interface?):

  • what base to use in the absence of a base prefix
    • Bases should be specified as a Base newtype around u32
      • impl TryFrom<u32> for Base, failing for 0, 1, and anything greater than 36
      • Give Base constants for common bases: DECIMAL, HEXADECIMAL, OCTAL, and BINARY
  • whether to allow a base prefix
  • whether to allow a base prefix for a different base than the "default" one
  • whether to require a base prefix?
  • whether to allow an uppercase base prefix
  • whether to allow underscores
  • whether to consume trailing underscores
    • Should this always be done?
  • whether to allow a sign
  • whether to allow a + sign
  • whether to allow -0 for unsigned types

• The scanner will always consume as many digits as there are at the start of the string, even if doing so would cause an overflow/underflow.