From b7d748ac5da525064fbb950e3bc63d3b3221d7cd Mon Sep 17 00:00:00 2001
From: Gwenhael Le Moine <gwenhael.le.moine@gmail.com>
Date: Wed, 24 Nov 2021 16:34:13 +0100
Subject: [PATCH] implement IFTE and IFT

---
 lib/core.rb                  |  1 +
 lib/dictionary.rb            |  8 ++++----
 lib/language/branch.rb       | 19 +++++++++++++++++++
 spec/language_branch_spec.rb | 29 +++++++++++++++++++++++++++++
 4 files changed, 53 insertions(+), 4 deletions(-)
 create mode 100644 lib/language/branch.rb
 create mode 100644 spec/language_branch_spec.rb

diff --git a/lib/core.rb b/lib/core.rb
index 910afe2..bed21b5 100644
--- a/lib/core.rb
+++ b/lib/core.rb
@@ -1,5 +1,6 @@
 require 'bigdecimal/math'
 
+require_relative './language/branch'
 require_relative './language/general'
 require_relative './language/mode'
 require_relative './language/operations'
diff --git a/lib/dictionary.rb b/lib/dictionary.rb
index 0e09a66..01fae40 100644
--- a/lib/dictionary.rb
+++ b/lib/dictionary.rb
@@ -101,8 +101,8 @@ module Rpl
       add( 'xor',     proc { |stack| Rpl::Core.xor( stack ) } )
       add( 'not',     proc { |stack| Rpl::Core.not( stack ) } )
       add( 'same',    proc { |stack| Rpl::Core.same( stack ) } )
-      add( 'true',    proc { |stack| Rpl::Core.true( stack ) } )
-      add( 'false',   proc { |stack| Rpl::Core.false( stack ) } )
+      add( 'true',    proc { |stack| Rpl::Core.true( stack ) } ) # specific
+      add( 'false',   proc { |stack| Rpl::Core.false( stack ) } ) # specific
 
       # STRING
       add( '->str',   proc { |stack| Rpl::Core.to_string( stack ) } )
@@ -124,8 +124,8 @@ module Rpl
       add( 'for',     proc { |stack| Rpl::Core.__todo( stack ) } ) # <start> <end> for <variable> <instructions> next|<step> step
       add( 'next',    proc { |stack| Rpl::Core.__todo( stack ) } ) # used with start and for
       add( 'step',    proc { |stack| Rpl::Core.__todo( stack ) } ) # used with start and for
-      add( 'ift',     proc { |stack| Rpl::Core.__todo( stack ) } ) # similar to if-then-end, <test-instruction> <true-instruction> ift
-      add( 'ifte',    proc { |stack| Rpl::Core.__todo( stack ) } ) # similar to if-then-else-end, <test-instruction> <true-instruction> <false-instruction> ifte
+      add( 'ift',     proc { |stack| Rpl::Core.ift( stack, self ) } )
+      add( 'ifte',    proc { |stack| Rpl::Core.ifte( stack, self ) } )
       add( 'do',      proc { |stack| Rpl::Core.__todo( stack ) } ) # do <instructions> until <condition> end
       add( 'until',   proc { |stack| Rpl::Core.__todo( stack ) } ) # used with do
       add( 'while',   proc { |stack| Rpl::Core.__todo( stack ) } ) # while <test-instruction> repeat <loop-instructions> end
diff --git a/lib/language/branch.rb b/lib/language/branch.rb
new file mode 100644
index 0000000..1278eb4
--- /dev/null
+++ b/lib/language/branch.rb
@@ -0,0 +1,19 @@
+module Rpl
+  module Core
+    module_function
+
+    # similar to if-then-end, <test-instruction> <true-instruction> ift
+    def ift( stack, dictionary )
+      ifte( stack << { type: :word, value: 'nop' }, dictionary )
+    end
+
+    # similar to if-then-else-end, <test-instruction> <true-instruction> <false-instruction> ifte
+    def ifte( stack, dictionary )
+      stack, args = Rpl::Core.stack_extract( stack, [%i[program word], %i[program word], %i[boolean]] )
+
+      stack << args[ args[2][:value] ? 1 : 0 ]
+
+      Rpl::Core.eval( stack, dictionary )
+    end
+  end
+end
diff --git a/spec/language_branch_spec.rb b/spec/language_branch_spec.rb
new file mode 100644
index 0000000..ae2e9fa
--- /dev/null
+++ b/spec/language_branch_spec.rb
@@ -0,0 +1,29 @@
+# coding: utf-8
+# frozen_string_literal: true
+
+require 'test/unit'
+
+require_relative '../lib/core'
+require_relative '../lib/dictionary'
+require_relative '../lib/parser'
+require_relative '../lib/runner'
+
+class TestLanguageBranch < Test::Unit::TestCase
+  def test_ifte
+    stack = Rpl::Core.ifte( [{ type: :boolean, value: true },
+                             { type: :program, value: '« 2 3 + »' },
+                             { type: :program, value: '« 2 3 - »' }],
+                            Rpl::Dictionary.new )
+
+    assert_equal [{ value: 5, type: :numeric, base: 10 }],
+                 stack
+
+    stack = Rpl::Core.ifte( [{ type: :boolean, value: false },
+                             { type: :program, value: '« 2 3 + »' },
+                             { type: :program, value: '« 2 3 - »' }],
+                            Rpl::Dictionary.new )
+
+    assert_equal [{ value: -1, type: :numeric, base: 10 }],
+                 stack
+  end
+end