Class: UnitMeasurements::Parser

Inherits:

Object

• Object
• UnitMeasurements::Parser

Defined in:

lib/unit_measurements/parser.rb

Overview

The UnitMeasurements::Parser class provides methods for parsing strings to extract quantity and associated unit. It can handle various formats, including complex numbers, scientific numbers, and rational numbers for the quantity.

See Also:

• Measurement

Author:

• Harshal V. Ladhe

Since:

• 1.0.0

Constant Summary

UNIT_REGEX =

Matches any character sequence that does not consist of digits, whitespace, or forward slashes.

Author:

• Harshal V. Ladhe

Since:

• 1.0.0

/
  (                    # Start of the capturing group
    [^\d\s\/]          # Match any character that is not a digit, whitespace, or a forward slash
    .*                 # Match zero or more of any character (except for a newline)
  )                    # End of the capturing group
/x.freeze

SCIENTIFIC_NUMBER =

Matches scientific numbers (e.g., 1.23e-4).

Author:

• Harshal V. Ladhe

Since:

• 1.0.0

/
  (                    # Start of a capturing group (denoted by parentheses)
    [+-]?              # Match an optional plus or minus sign (+ or -)
    \d*                # Match zero or more digits
    \.?                # Match an optional dot (.)
    \d+                # Match one or more digits
    (?:                # Start of a non-capturing group
      [Ee]             # Match either 'E' or 'e'
      [+-]?            # Match an optional plus or minus sign (+ or -)
    )?                 # End of the non-capturing group; ? makes it optional
    \d*                # Match zero or more digits
  )                    # End of the capturing group
/x.freeze

RATIONAL_NUMBER =

Matches rational numbers (e.g., 1/2).

Author:

• Harshal V. Ladhe

Since:

• 1.0.0

/
  (                    # Start of the first capturing group
    [+-]?              # Match an optional plus or minus sign (+ or -)
    \d+                # Match one or more digits
    \s+                # Match one or more whitespace characters
  )?                   # End of the first capturing group
  (                    # Start of the second capturing group (the fraction part)
    (\d+)              # Start of the third capturing group (one or more digits, the numerator)
    \/                 # Match a forward slash - the division symbol
    (\d+)              # Start of the fourth capturing group (one or more digits, the denominator)
  )                    # End of the second capturing group (the fraction part)
/x.freeze

COMPLEX_NUMBER =

Matches complex numbers (e.g., 1-2i).

Author:

• Harshal V. Ladhe

Since:

• 1.0.0

/
  #{SCIENTIFIC_NUMBER} # Pattern for scientific number
  #{SCIENTIFIC_NUMBER} # Pattern for scientific number
  i                    # Match the letter 'i' (the imaginary unit)
/x.freeze

SCIENTIFIC_REGEX =

Matches strings containing scientific numbers and unit.

Author:

• Harshal V. Ladhe

Since:

• 1.0.0

/
  \A                   # Anchor at the start of the string
  #{SCIENTIFIC_NUMBER} # Match a scientific number (as defined earlier)
  \s*                  # Match zero or more whitespace characters
  #{UNIT_REGEX}?       # Match a unit, the '?' makes it optional
  \z                   # Anchor at the end of the string
/x.freeze

RATIONAL_REGEX =

Matches strings containing rational numbers and unit.

Author:

• Harshal V. Ladhe

Since:

• 1.0.0

/
  \A                   # Anchor at the start of the string
  #{RATIONAL_NUMBER}   # Match a rational number (as defined earlier)
  \s*                  # Match zero or more whitespace characters
  #{UNIT_REGEX}?       # Match a unit, the '?' makes it optional
  \z
/x.freeze

COMPLEX_REGEX =

Matches strings containing complex numbers and unit.

Author:

• Harshal V. Ladhe

Since:

• 1.0.0

/
  \A                   # Anchor at the start of the string
  #{COMPLEX_NUMBER}    # Match a complex number (as defined earlier)
  \s*                  # Match zero or more whitespace characters
  #{UNIT_REGEX}?       # Match a unit, the '?' makes it optional
  \z
/x.freeze

Class Method Summary

• .parse(string) ⇒ Array<Numeric, String|NilClass>

  Parses a string to extract a quantity and its associated unit.

Class Method Details

.parse(string) ⇒ Array<Numeric, String|NilClass>

Parses a string to extract a quantity and its associated unit. This method first extracts a quantity and converts it to Float before returning it.

To get the correct parsed results, you must first normalize the string with Normalizer if using the parser standalone.

Examples:

Parsing string representing a complex number:

UnitMeasurements::Parser.parse("1+2i m")
=> [(1.0+2.0i), "m"]

Parsing string representing a rational number:

UnitMeasurements::Parser.parse("1/2 m")
=> [0.5, "m"]

Parsing string representing a mixed rational number:

UnitMeasurements::Parser.parse("2 1/2 km")
=> [2.5, "km"]

Parsing string representing a scientific number:

UnitMeasurements::Parser.parse("1e+2 km")
=> [100.0, "km"]

Parameters:

• string (String) —

  The input string containing a quantity and an optional unit.

Returns:

• (Array<Numeric, String|NilClass>) —

  The parsed quantity and the unit associated with it (or nil if no unit is specified in the string).

Raises:

• (ParseError) —

  If the string is invalid and cannot be parsed.

See Also:

• Measurement
• Normalizer

Author:

• Harshal V. Ladhe

Since:

• 1.0.0

# File 'lib/unit_measurements/parser.rb', line 144

def parse(string)
  case string
  when COMPLEX_REGEX    then parse_complex(string)
  when SCIENTIFIC_REGEX then parse_scientific(string)
  when RATIONAL_REGEX   then parse_rational(string)
  else                       raise ParseError, string
  end
end