From 03da1e329d86cf9ce23338112aee124905825fe1 Mon Sep 17 00:00:00 2001
From: "Kartik K. Agaram" <vc@akkartik.com>
Date: Sat, 16 May 2015 13:03:59 -0700
Subject: 1382 - implement continuations

---
 048continuation.cc | 76 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 76 insertions(+)
 create mode 100644 048continuation.cc

diff --git a/048continuation.cc b/048continuation.cc
new file mode 100644
index 00000000..a178422f
--- /dev/null
+++ b/048continuation.cc
@@ -0,0 +1,76 @@
+
+:(before "End Globals")
+map<index_t, call_stack> Continuation;
+index_t Next_continuation_id = 0;
+:(before "End Setup")
+Continuation.clear();
+Next_continuation_id = 0;
+
+:(before "End Mu Types Initialization")
+type_number continuation = Type_number["continuation"] = Next_type_number++;
+Type[continuation].name = "continuation";
+
+:(before "End Primitive Recipe Declarations")
+CURRENT_CONTINUATION,
+:(before "End Primitive Recipe Numbers")
+Recipe_number["current-continuation"] = CURRENT_CONTINUATION;
+:(before "End Primitive Recipe Implementations")
+case CURRENT_CONTINUATION: {
+  Continuation[Next_continuation_id] = Current_routine->calls;  // deep copy because calls have no pointers
+  products.resize(1);
+  products.at(0).push_back(Next_continuation_id);
+  ++Next_continuation_id;
+  break;
+}
+
+:(before "End Primitive Recipe Declarations")
+CONTINUE_FROM,
+:(before "End Primitive Recipe Numbers")
+Recipe_number["continue-from"] = CONTINUE_FROM;
+:(before "End Primitive Recipe Implementations")
+case CONTINUE_FROM: {
+  assert(ingredients.at(0).size() == 1);  // scalar
+  index_t c = ingredients.at(0).at(0);
+  Current_routine->calls = Continuation[c];  // deep copy because calls have no pointers
+  // refresh instruction_counter to next instruction after current-continuation
+  instruction_counter = current_step_index()+1;
+  continue;  // skip the rest of this instruction
+}
+
+:(scenario continuation)
+# simulate a loop using continuations
+recipe main [
+  1:number <- copy 0:literal
+  2:continuation <- current-continuation
+  {
+#?     $print 1:number
+    3:boolean <- greater-or-equal 1:number, 3:literal
+    break-if 3:boolean
+    1:number <- add 1:number, 1:literal
+    continue-from 2:continuation  # loop
+  }
+]
++mem: storing 1 in location 1
++mem: storing 2 in location 1
++mem: storing 3 in location 1
+-mem: storing 4 in location 1
+
+:(scenario continuation_inside_caller)
+recipe main [
+  1:number <- copy 0:literal
+  2:continuation <- loop-body
+  {
+    3:boolean <- greater-or-equal 1:number, 3:literal
+    break-if 3:boolean
+    continue-from 2:continuation  # loop
+  }
+]
+
+recipe loop-body [
+  4:continuation <- current-continuation
+  1:number <- add 1:number, 1:literal
+]
++mem: storing 1 in location 1
++mem: storing 2 in location 1
++mem: storing 3 in location 1
+-mem: storing 4 in location 1
-- 
cgit 1.4.1-2-gfad0