1  # coding: utf-8
   2  # frozen_string_literal: true
   3 
   4 
   5 
   6  module Umu
   7 
   8  module ConcreteSyntax
   9 
  10  module Core
  11 
  12  module Expression
  13 
  14  module Nary
  15 
  16  module Branch
  17 
  18  module Rule
  19 
  20  class If < Abstraction::HasHead
  21      alias head_expr head
  22 
  23      def initialize(loc, head_expr, body_expr)
  24          ASSERT.kind_of head_expr,   CSCE::Abstract
  25          ASSERT.kind_of body_expr,   CSCE::Abstract
  26 
  27          super
  28      end
  29 
  30 
  31      def to_s
  32          format "%s %%THEN %s", self.head_expr, self.body_expr
  33      end
  34 
  35 
  36      def pretty_print(q)
  37          q.pp self.head_expr
  38          q.text ' %THEN '
  39          q.pp self.body_expr
  40      end
  41  end
  42 
  43  end # Umu::ConcreteSyntax::Core::Expression::Nary::Branch::Rule
  44 
  45 
  46 
  47  class If < Expression::Abstract
  48      attr_reader :if_rule, :elsif_rules, :else_expr
  49 
  50 
  51      def initialize(loc, if_rule, elsif_rules, else_expr)
  52          ASSERT.kind_of if_rule,     Nary::Branch::Rule::If
  53          ASSERT.kind_of elsif_rules, ::Array
  54          ASSERT.kind_of else_expr,   CSCE::Abstract
  55 
  56          super(loc)
  57 
  58          @if_rule        = if_rule
  59          @elsif_rules    = elsif_rules
  60          @else_expr      = else_expr
  61      end
  62 
  63 
  64      def to_s
  65          rules_string = if self.elsif_rules.empty?
  66                              ' '
  67                          else
  68                              format(" %s ",
  69                                  self.elsif_rules.map { |rule|
  70                                      '%ELSIF ' + rule.to_s
  71                                  }.join(' ')
  72                              )
  73                          end
  74 
  75          format("%%IF %s%s%%ELSE %s",
  76              self.if_rule.to_s, 
  77              rules_string,
  78              self.else_expr.to_s
  79          )
  80      end
  81 
  82 
  83      def pretty_print(q)
  84          PRT.group q, bb:'(', eb:')' do
  85              PRT.group q, bb:'%IF ' do
  86                  q.pp self.if_rule
  87              end
  88 
  89              self.elsif_rules.each do |rule|
  90                  q.breakable
  91 
  92                  PRT.group q, bb:'%ELSIF ' do
  93                      q.pp rule
  94                  end
  95              end
  96 
  97              q.breakable
  98 
  99              PRT.group q, bb:'%ELSE ' do
 100                  q.pp self.else_expr
 101              end
 102          end
 103      end
 104 
 105 
 106  private
 107 
 108      def __desugar__(env, event)
 109          new_env = env.enter event
 110 
 111          ASCE.make_if(
 112              self.loc,
 113 
 114              ([self.if_rule] + self.elsif_rules).map { |rule|
 115                  ASSERT.kind_of rule, Nary::Branch::Rule::If
 116 
 117                  ASCE.make_rule(
 118                      rule.loc,
 119                      rule.head_expr.desugar(new_env),
 120                      rule.body_expr.desugar(new_env)
 121                  )
 122              },
 123 
 124              self.else_expr.desugar(new_env)
 125          )
 126      end
 127  end
 128 
 129  end # Umu::ConcreteSyntax::Core::Expression::Nary::Branch
 130 
 131  end # Umu::ConcreteSyntax::Core::Expression::Nary
 132 
 133 
 134  module_function
 135 
 136      def make_if(loc, if_rule, elsif_rules, else_expr)
 137          ASSERT.kind_of loc,         LOC::Entry
 138          ASSERT.kind_of if_rule,     Nary::Branch::Rule::If
 139          ASSERT.kind_of elsif_rules, ::Array
 140          ASSERT.kind_of else_expr,   CSCE::Abstract
 141 
 142          Nary::Branch::If.new(loc, if_rule, elsif_rules, else_expr).freeze
 143      end
 144 
 145 
 146      def make_if_rule(loc, head_expr, body_expr)
 147          ASSERT.kind_of loc,         LOC::Entry
 148          ASSERT.kind_of head_expr,   CSCE::Abstract
 149          ASSERT.kind_of body_expr,   CSCE::Abstract
 150 
 151          Nary::Branch::Rule::If.new(
 152              loc, head_expr, body_expr 
 153          ).freeze
 154      end
 155 
 156  end # Umu::ConcreteSyntax::Core::Expression
 157 
 158  end # Umu::ConcreteSyntax::Core
 159 
 160  end # Umu::ConcreteSyntax
 161 
 162  end # Umu