Class: Sevgi::Sundries::Interval

Inherits:
Object
  • Object
show all
Defined in:
lib/sevgi/sundries/ruler.rb

Overview

A one-dimensional interval divided into equal units.

The compact reader names are part of the domain vocabulary: u is the unit length, n is the interval count, d is total distance, and h is the midpoint distance.

Examples:

Interval geometry

# <---------------- d = n x u ---------------->
# |---------+---------+---------+---------|
#           <--- u --->
interval = Sevgi::Sundries::Interval[3, 4]
interval.d # => 12.0

Direct Known Subclasses

Ruler

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(e, n) ⇒ void

Creates an interval.

Parameters:

  • e (Numeric, #length) —

    unit length or an object exposing length

  • n (Integer) —

    non-negative interval count

Raises:

  • (Sevgi::ArgumentError) —

    when count is not a non-negative integer

  • (Sevgi::ArgumentError) —

    when the unit object does not expose length

  • (Sevgi::ArgumentError) —

    when the measured unit length is not numeric

  • (Sevgi::ArgumentError) —

    when the measured unit length is not finite

  • (Sevgi::ArgumentError) —

    when the measured unit length is not positive



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# File 'lib/sevgi/sundries/ruler.rb', line 46

def initialize(e, n)
  @n = non_negative_integer(n, "Interval count")
  @u = measure(e)
end

Instance Attribute Details

#n ⇒ Integer (readonly)

Returns the interval count.

Returns:

  • (Integer) 


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# File 'lib/sevgi/sundries/ruler.rb', line 31

def n
  @n
end

#u ⇒ Float (readonly)

Returns the unit length.

Returns:

  • (Float) 


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# File 'lib/sevgi/sundries/ruler.rb', line 35

def u
  @u
end

Class Method Details

.[](e, n) ⇒ Sevgi::Sundries::Interval

Builds an interval using bracket syntax.

Parameters:

  • e (Numeric, #length) —

    unit length or an object exposing length

  • n (Integer) —

    non-negative interval count

Returns:

Raises:

  • (Sevgi::ArgumentError) —

    when count is not a non-negative integer

  • (Sevgi::ArgumentError) —

    when the unit object does not expose length

  • (Sevgi::ArgumentError) —

    when the measured unit length is not numeric

  • (Sevgi::ArgumentError) —

    when the measured unit length is not finite

  • (Sevgi::ArgumentError) —

    when the measured unit length is not positive



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# File 'lib/sevgi/sundries/ruler.rb', line 27

def self.[](e, n) = new(e, n)

Instance Method Details

#[](i) ⇒ Float?

Returns a major tick distance by index.

Parameters:

  • i (Integer) —

    tick index

Returns:

  • (Float, nil) —

    distance from the interval origin, or nil when out of range



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# File 'lib/sevgi/sundries/ruler.rb', line 54

def [](i) = ds[i]

#count(length) ⇒ Integer

Counts how many whole lengths fit into this interval.

Parameters:

  • length (Numeric) —

    candidate length

Returns:

  • (Integer)

Raises:

  • (Sevgi::ArgumentError) —

    when length is not numeric

  • (Sevgi::ArgumentError) —

    when length is not finite

  • (Sevgi::ArgumentError) —

    when length is not positive



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# File 'lib/sevgi/sundries/ruler.rb', line 62

def count(length) = (d / positive_number(length, "Interval count length")).to_i

#d ⇒ Float Also known as: length

Returns the total interval distance.

Returns:

  • (Float) 


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# File 'lib/sevgi/sundries/ruler.rb', line 66

def d = @d ||= n * u

#ds ⇒ Array<Float>

Returns major tick distances, including both endpoints. The memoized collection is frozen and must be treated as immutable.

Returns:

  • (Array<Float>) —

    frozen major tick distances



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# File 'lib/sevgi/sundries/ruler.rb', line 71

def ds = @ds ||= Array.new(n + 1) { |i| i * u }.freeze

#h ⇒ Float

Returns the midpoint distance.

Returns:

  • (Float) 


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# File 'lib/sevgi/sundries/ruler.rb', line 75

def h = @h ||= d / 2.0

#hs ⇒ Array<Float>

Returns midpoint tick distances for each interval segment. The memoized collection is frozen and must be treated as immutable.

Returns:

  • (Array<Float>) —

    frozen midpoint tick distances



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# File 'lib/sevgi/sundries/ruler.rb', line 80

def hs = @hs ||= Array.new(n) { |i| u * (0.5 + i) }.freeze

#nds ⇒ Integer

Returns the last major tick index.

Returns:

  • (Integer) 


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# File 'lib/sevgi/sundries/ruler.rb', line 84

def nds = @nds ||= ds.size - 1

#nhs ⇒ Integer

Returns the last midpoint tick index.

Returns:

  • (Integer) 


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# File 'lib/sevgi/sundries/ruler.rb', line 88

def nhs = @nhs ||= hs.size - 1