Class: UnitMeasurements::Parser

Inherits:
Object
  • Object
show all
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:

Author:

Since:

  • 1.0.0

Constant Summary collapse

UNIT_REGEX =

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

Author:

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:

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:

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:

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:

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:

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:

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 collapse

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:

Author:

Since:

  • 1.0.0



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# 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

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

Parses a string representing a complex number with an optional unit.

Parameters:

  • string (String) —

    The input string containing a complex number and an optional unit.

Returns:

  • (Array<Numeric, String|NilClass>) —

    The parsed complex number and the associated unit (or nil if no unit is specified in the string).

Author:

Since:

  • 1.0.0



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# File 'lib/unit_measurements/parser.rb', line 167

def parse_complex(string)
  real, imaginary, unit = string.match(COMPLEX_REGEX)&.captures
  quantity = Complex(real.to_f, imaginary.to_f)

  [quantity, unit]
end

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

Parses a string representing a rational number with an optional unit.

Parameters:

  • string (String) —

    The input string containing a rational number and an optional unit.

Returns:

  • (Array<Numeric, String|NilClass>) —

    The parsed rational number and the associated unit (or nil if no unit is specified in the string).

Author:

Since:

  • 1.0.0



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# File 'lib/unit_measurements/parser.rb', line 205

def parse_rational(string)
  whole, _, numerator, denominator, unit = string.match(RATIONAL_REGEX)&.captures

  if numerator && denominator
    numerator = numerator.to_f + (denominator.to_f * whole.to_f)
    denominator = denominator.to_f
    quantity = Rational(numerator, denominator).to_f
  else
    quantity = whole.to_f
  end

  [quantity, unit]
end

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

Parses a string representing a scientific number with an optional unit.

Parameters:

  • string (String) —

    The input string containing a scientific number and an optional unit.

Returns:

  • (Array<Numeric, String|NilClass>) —

    The parsed scientific number and the associated unit (or nil if no unit is specified in the string).

Author:

Since:

  • 1.0.0



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# File 'lib/unit_measurements/parser.rb', line 186

def parse_scientific(string)
  whole, unit = string.match(SCIENTIFIC_REGEX)&.captures
  quantity = whole.to_f

  [quantity, unit]
end