Class: Semdiff::AlgebraCompiler

Inherits:
Prism::MutationCompiler
  • Object
show all
Includes:
Prism::DSL, CompilerUtils
Defined in:
lib/semdiff/algebra_compiler.rb

Overview

AlgebraCompiler is a compiler that simplifies expressions with algebraic relations based on type information.

Expression Canonical Form

b + a a + b # commutativity c * a a * c # commutativity ( a + b ) + c a + b + c # associativity ( x * b ) + ( x * c ) x * ( b + c ) # distributivity x - ( - y ) x + y # negation ( x ** m ) * ( x ** n ) x *( m + n ) # exponentials ( a - b ) - b a - 2 b # optimization

</code>

Examples:

```ruby

Constant Summary collapse

COMMUTATIVE_OPS = 
%i[+ *].freeze
ASSOCIATIVE_OPS = 
%i[+ *].freeze

Instance Method Summary collapse

Methods included from CompilerUtils

inherit_newline

Constructor Details

#initialize(node_types) ⇒ AlgebraCompiler

Returns a new instance of AlgebraCompiler.



25
26
27
28
 
# File 'lib/semdiff/algebra_compiler.rb', line 25

def initialize(node_types)
  @node_types = node_types
  super()
end

Instance Method Details

#visit_call_node(node) ⇒ Object 



30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
 
# File 'lib/semdiff/algebra_compiler.rb', line 30

def visit_call_node(node)
  receiver  = visit(node.receiver)
  arguments = visit(node.arguments)
  block     = visit(node.block)
  result    = nil

  if COMMUTATIVE_OPS.include?(node.name) &&
     receiver &&
     arguments&.arguments&.size == 1 &&
     block.nil?
    if ASSOCIATIVE_OPS.include?(node.name)
      operands = flatten_associative_operation(node.name, receiver, arguments.arguments.first)
      if operands.all? { |op| numeric?(op) }
        sorted_operands = operands.sort_by { |op| sort_key(op) }
        result = rebuild_associative_operation(node, node.name, sorted_operands)
      end
    else
      lhs = receiver
      rhs = arguments.arguments.first
      if numeric?(lhs) && numeric?(rhs) && should_swap?(lhs, rhs)
        result = node.copy(
          receiver: rhs,
          arguments: arguments_node(
            node_id: arguments.node_id,
            source: arguments.send(:source),
            location: arguments.location,
            flags: arguments.send(:flags),
            arguments: [lhs]
          )
        )
      end
    end
  end

  if result
    CompilerUtils.inherit_newline(node, result)
  else
    node.copy(receiver: receiver, arguments: arguments, block: block)
  end
end

#visit_parentheses_node(node) ⇒ Object 



71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
 
# File 'lib/semdiff/algebra_compiler.rb', line 71

def visit_parentheses_node(node)
  if node.multiple_statements?
    statements = visit_all(node.body.body)
    body = node.body.copy(body: statements)
    node.copy(body: body)
  else
    inner = visit(node.body.body.first)
    if inner.type == :call_node &&
       ASSOCIATIVE_OPS.include?(inner.name) &&
       inner.arguments&.arguments&.size == 1 &&
       numeric?(inner.receiver) &&
       numeric?(inner.arguments.arguments.first)
      inner
    else
      body = node.body.copy(body: [inner])
      node.copy(body: body)
    end
  end
end