Class: CAS::Ln

Inherits:
Op
  • Object
show all
Defined in:
lib/functions/fnc-trsc.rb

Overview

Representation for the `log(x)` function. It is implemented as a `CAS::Op`

Instance Attribute Summary

Attributes inherited from Op

#x

Class Method Summary collapse

Instance Method Summary collapse

Methods inherited from Op

#!=, #*, #**, #+, #-, #[email protected], #/, #==, #args, #as_proc, #depend?, #dot_graph, #equal, #greater, #greater_equal, #initialize, #inspect, #limit, numeric_to_const, simplify_dict, #simplify_dictionary, #smaller, #smaller_equal, #subs, #to_c_lib

Constructor Details

This class inherits a constructor from CAS::Op

Class Method Details

.init_simplify_dictObject


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# File 'lib/functions/fnc-trsc.rb', line 181

def self.init_simplify_dict
  @simplify_dict = {
    CAS::Zero => CAS.invert(CAS::Infinity),
    CAS::One => CAS::Zero,
    CAS::E => CAS::One
  }
end

Instance Method Details

#call(f) ⇒ Object

Call resolves the operation tree in a `Numeric` (if `Fixnum`) or `Float` (depends upon promotions). As input, it requires an hash with `CAS::Variable` or `CAS::Variable#name` as keys, and a `Numeric` as a value

* **argument**: `Hash` with feed dictionary
* **returns**: `Numeric`

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# File 'lib/functions/fnc-trsc.rb', line 156

def call(f)
  # I'm leaving to Math the honor
  # of handling negative values...
  CAS::Help.assert(f, Hash)
  Math::log(@x.call(f))
end

#diff(v) ⇒ Object

Return the derivative of the `log(x)` function using the chain rule. The input is a `CAS::Op` because it can handle derivatives with respect to functions.

“`

d              f'(x)

– log(f(x)) = ——- dx f(x) “`

* **argument**: `CAS::Op` object of the derivative
* **returns**: `CAS::Op` a derivated object, or `CAS::Zero` for constants

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# File 'lib/functions/fnc-trsc.rb', line 141

def diff(v)
  if @x.depend? v
    return CAS::One / @x
  else
    return CAS::Zero
  end
end

#simplifyObject

Simplification callback. It simplify the subgraph of each node until all possible simplification are performed (thus the execution time is not deterministic).

* **returns**: `CAS::Op` simplified version

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# File 'lib/functions/fnc-trsc.rb', line 175

def simplify
  super
  return @x.x if @x.is_a? CAS::Exp
  return self.simplify_dictionary
end

#to_codeObject

Convert expression to code (internal, for `CAS::Op#to_proc` method)

* **returns**: `String` that represent Ruby code to be parsed in `CAS::Op#to_proc`

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# File 'lib/functions/fnc-trsc.rb', line 192

def to_code
  "Math::log(#{@x.to_code})"
end

#to_latexObject

Returns the latex representation of the current Op.

* **returns**: `String`

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# File 'lib/functions/fnc-trsc.rb', line 199

def to_latex
  "\\log\\left( #{@x.to_latex} \\right)"
end

#to_sObject

Convert expression to string

* **returns**: `String` to print on screen

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# File 'lib/functions/fnc-trsc.rb', line 166

def to_s
  "log(#{@x})"
end