1206 - 'wait' state for synchronizing routines

I think I have enough now to port channels over.

36 files changed, 155 insertions, 58 deletions

diff --git a/cpp/.traces/brace_conversion b/cpp/.traces/brace_conversion
index 580f334f..e1852440 100644
--- a/cpp/.traces/brace_conversion
+++ b/cpp/.traces/brace_conversion
@@ -1,5 +1,5 @@
 parse/0: label: {
-parse/0: instruction: 30
+parse/0: instruction: 31
 parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
 parse/0:   product: {name: "1", value: 0, type: 1, properties: ["1": "integer"]}
diff --git a/cpp/.traces/brace_conversion_and_run b/cpp/.traces/brace_conversion_and_run
index 8250e7a4..78844009 100644
--- a/cpp/.traces/brace_conversion_and_run
+++ b/cpp/.traces/brace_conversion_and_run
@@ -9,7 +9,7 @@ parse/0: instruction: 13
 parse/0:   ingredient: {name: "1", value: 0, type: 1, properties: ["1": "integer"]}
 parse/0:   ingredient: {name: "1", value: 0, type: 0, properties: ["1": "literal"]}
 parse/0:   product: {name: "3", value: 0, type: 3, properties: ["3": "boolean"]}
-parse/0: instruction: 31
+parse/0: instruction: 32
 parse/0:   ingredient: {name: "3", value: 0, type: 3, properties: ["3": "boolean"]}
 parse/0: instruction: 4
 parse/0:   ingredient: {name: "2", value: 0, type: 1, properties: ["2": "integer"]}
@@ -19,7 +19,7 @@ parse/0: instruction: 3
 parse/0:   ingredient: {name: "1", value: 0, type: 1, properties: ["1": "integer"]}
 parse/0:   ingredient: {name: "1", value: 0, type: 0, properties: ["1": "literal"]}
 parse/0:   product: {name: "1", value: 0, type: 1, properties: ["1": "integer"]}
-parse/0: instruction: 33
+parse/0: instruction: 34
 parse/0: label: }
 parse/0: instruction: 1
 parse/0:   ingredient: {name: "2", value: 0, type: 1, properties: ["2": "integer"]}
diff --git a/cpp/.traces/break_cascading b/cpp/.traces/break_cascading
index c21cda61..be0dcb75 100644
--- a/cpp/.traces/break_cascading
+++ b/cpp/.traces/break_cascading
@@ -2,10 +2,10 @@ parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
 parse/0:   product: {name: "1", value: 0, type: 1, properties: ["1": "integer"]}
 parse/0: label: {
-parse/0: instruction: 30
+parse/0: instruction: 31
 parse/0: label: }
 parse/0: label: {
-parse/0: instruction: 30
+parse/0: instruction: 31
 parse/0: label: }
 brace/0: 1000: push (open, 1)
 brace/0: push (close, 3)
diff --git a/cpp/.traces/break_cascading2 b/cpp/.traces/break_cascading2
index 8d0d42b9..a4bf4668 100644
--- a/cpp/.traces/break_cascading2
+++ b/cpp/.traces/break_cascading2
@@ -5,13 +5,13 @@ parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
 parse/0:   product: {name: "2", value: 0, type: 1, properties: ["2": "integer"]}
 parse/0: label: {
-parse/0: instruction: 30
+parse/0: instruction: 31
 parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
 parse/0:   product: {name: "3", value: 0, type: 1, properties: ["3": "integer"]}
 parse/0: label: }
 parse/0: label: {
-parse/0: instruction: 30
+parse/0: instruction: 31
 parse/0: label: }
 brace/0: 1000: push (open, 2)
 brace/0: push (close, 5)
diff --git a/cpp/.traces/break_empty_block b/cpp/.traces/break_empty_block
index ee11f3e6..5dc33d5f 100644
--- a/cpp/.traces/break_empty_block
+++ b/cpp/.traces/break_empty_block
@@ -2,7 +2,7 @@ parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
 parse/0:   product: {name: "1", value: 0, type: 1, properties: ["1": "integer"]}
 parse/0: label: {
-parse/0: instruction: 30
+parse/0: instruction: 31
 parse/0: label: }
 brace/0: 1000: push (open, 1)
 brace/0: push (close, 3)
diff --git a/cpp/.traces/break_if b/cpp/.traces/break_if
index 5e379313..ba84c1bb 100644
--- a/cpp/.traces/break_if
+++ b/cpp/.traces/break_if
@@ -5,14 +5,14 @@ parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
 parse/0:   product: {name: "2", value: 0, type: 1, properties: ["2": "integer"]}
 parse/0: label: {
-parse/0: instruction: 31
+parse/0: instruction: 32
 parse/0:   ingredient: {name: "2", value: 0, type: 1, properties: ["2": "integer"]}
 parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
 parse/0:   product: {name: "3", value: 0, type: 1, properties: ["3": "integer"]}
 parse/0: label: }
 parse/0: label: {
-parse/0: instruction: 30
+parse/0: instruction: 31
 parse/0: label: }
 brace/0: 1000: push (open, 2)
 brace/0: push (close, 5)
diff --git a/cpp/.traces/break_label b/cpp/.traces/break_label
index b4e5d5a4..1f66321f 100644
--- a/cpp/.traces/break_label
+++ b/cpp/.traces/break_label
@@ -2,7 +2,7 @@ parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
 parse/0:   product: {name: "1", value: 0, type: 1, properties: ["1": "integer"]}
 parse/0: label: {
-parse/0: instruction: 30
+parse/0: instruction: 31
 parse/0:   ingredient: {name: "+foo", value: 0, type: 0, properties: ["+foo": "offset"]}
 parse/0: label: }
 brace/0: 1000: push (open, 1)
diff --git a/cpp/.traces/break_nested b/cpp/.traces/break_nested
index 2d445d5d..2879c48a 100644
--- a/cpp/.traces/break_nested
+++ b/cpp/.traces/break_nested
@@ -5,7 +5,7 @@ parse/0: label: {
 parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
 parse/0:   product: {name: "2", value: 0, type: 1, properties: ["2": "integer"]}
-parse/0: instruction: 30
+parse/0: instruction: 31
 parse/0: label: {
 parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
diff --git a/cpp/.traces/break_nested_degenerate b/cpp/.traces/break_nested_degenerate
index 633b6ea0..d451959f 100644
--- a/cpp/.traces/break_nested_degenerate
+++ b/cpp/.traces/break_nested_degenerate
@@ -5,7 +5,7 @@ parse/0: label: {
 parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
 parse/0:   product: {name: "2", value: 0, type: 1, properties: ["2": "integer"]}
-parse/0: instruction: 30
+parse/0: instruction: 31
 parse/0: label: {
 parse/0: label: }
 parse/0: instruction: 1
diff --git a/cpp/.traces/break_nested_degenerate2 b/cpp/.traces/break_nested_degenerate2
index e32a341f..47f21f34 100644
--- a/cpp/.traces/break_nested_degenerate2
+++ b/cpp/.traces/break_nested_degenerate2
@@ -5,7 +5,7 @@ parse/0: label: {
 parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
 parse/0:   product: {name: "2", value: 0, type: 1, properties: ["2": "integer"]}
-parse/0: instruction: 30
+parse/0: instruction: 31
 parse/0: label: {
 parse/0: label: }
 parse/0: label: }
diff --git a/cpp/.traces/break_unless b/cpp/.traces/break_unless
index 16d7f12b..8557c249 100644
--- a/cpp/.traces/break_unless
+++ b/cpp/.traces/break_unless
@@ -5,7 +5,7 @@ parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
 parse/0:   product: {name: "2", value: 0, type: 1, properties: ["2": "integer"]}
 parse/0: label: {
-parse/0: instruction: 32
+parse/0: instruction: 33
 parse/0:   ingredient: {name: "2", value: 0, type: 1, properties: ["2": "integer"]}
 parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
diff --git a/cpp/.traces/buffer-append-works b/cpp/.traces/buffer-append-works
index 8f078ca0..dbd2345d 100644
--- a/cpp/.traces/buffer-append-works
+++ b/cpp/.traces/buffer-append-works
@@ -1,4 +1,4 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "location", value: 0, type: 0, properties: ["location": "type"]}
 parse/0:   ingredient: {name: "30", value: 0, type: 0, properties: ["30": "literal"]}
 parse/0:   product: {name: "default-space", value: 0, type: 2-5-1, properties: ["default-space": "address":"array":"location"]}
diff --git a/cpp/.traces/closure b/cpp/.traces/closure
index 62bbbd4e..ae880949 100644
--- a/cpp/.traces/closure
+++ b/cpp/.traces/closure
@@ -1,4 +1,4 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "location", value: 0, type: 0, properties: ["location": "type"]}
 parse/0:   ingredient: {name: "30", value: 0, type: 0, properties: ["30": "literal"]}
 parse/0:   product: {name: "default-space", value: 0, type: 2-5-1, properties: ["default-space": "address":"array":"location"]}
@@ -10,7 +10,7 @@ parse/0:   product: {name: "2", value: 0, type: 1, properties: ["2": "integer",
 parse/0: instruction: 1002
 parse/0:   ingredient: {name: "1", value: 0, type: 2-5-1, properties: ["1": "address":"array":"location", "names": "init-counter"]}
 parse/0:   product: {name: "3", value: 0, type: 1, properties: ["3": "integer", "raw": ]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "location", value: 0, type: 0, properties: ["location": "type"]}
 parse/0:   ingredient: {name: "30", value: 0, type: 0, properties: ["30": "literal"]}
 parse/0:   product: {name: "default-space", value: 0, type: 2-5-1, properties: ["default-space": "address":"array":"location"]}
@@ -22,7 +22,7 @@ parse/0:   ingredient: {name: "3", value: 0, type: 0, properties: ["3": "literal
 parse/0:   product: {name: "y", value: 0, type: 1, properties: ["y": "integer"]}
 parse/0: instruction: 28
 parse/0:   ingredient: {name: "default-space", value: 0, type: 2-5-1, properties: ["default-space": "address":"array":"location"]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "space", value: 0, type: 0, properties: ["space": "literal"]}
 parse/0:   ingredient: {name: "30", value: 0, type: 0, properties: ["30": "literal"]}
 parse/0:   product: {name: "default-space", value: 0, type: 2-5-1, properties: ["default-space": "address":"array":"location"]}
diff --git a/cpp/.traces/interpolate-at-end b/cpp/.traces/interpolate-at-end
index a6dcb375..c0093a24 100644
--- a/cpp/.traces/interpolate-at-end
+++ b/cpp/.traces/interpolate-at-end
@@ -1,7 +1,7 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "hello, _", value: 0, type: 0, properties: ["hello, _": "literal-string"]}
 parse/0:   product: {name: "1", value: 0, type: 2-5-4, properties: ["1": "address":"array":"character", "raw": ]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "abc", value: 0, type: 0, properties: ["abc": "literal-string"]}
 parse/0:   product: {name: "2", value: 0, type: 2-5-4, properties: ["2": "address":"array":"character", "raw": ]}
 parse/0: instruction: 107
diff --git a/cpp/.traces/interpolate-at-start b/cpp/.traces/interpolate-at-start
index ce99463f..69b84ff5 100644
--- a/cpp/.traces/interpolate-at-start
+++ b/cpp/.traces/interpolate-at-start
@@ -1,7 +1,7 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "_, hello!", value: 0, type: 0, properties: ["_, hello!": "literal-string"]}
 parse/0:   product: {name: "1", value: 0, type: 2-5-4, properties: ["1": "address":"array":"character", "raw": ]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "abc", value: 0, type: 0, properties: ["abc": "literal-string"]}
 parse/0:   product: {name: "2", value: 0, type: 2-5-4, properties: ["2": "address":"array":"character", "raw": ]}
 parse/0: instruction: 107
diff --git a/cpp/.traces/interpolate-works b/cpp/.traces/interpolate-works
index a9f9b7fb..b033c1fd 100644
--- a/cpp/.traces/interpolate-works
+++ b/cpp/.traces/interpolate-works
@@ -1,7 +1,7 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "abc _", value: 0, type: 0, properties: ["abc _": "literal-string"]}
 parse/0:   product: {name: "1", value: 0, type: 2-5-4, properties: ["1": "address":"array":"character", "raw": ]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "def", value: 0, type: 0, properties: ["def": "literal-string"]}
 parse/0:   product: {name: "2", value: 0, type: 2-5-4, properties: ["2": "address":"array":"character", "raw": ]}
 parse/0: instruction: 107
diff --git a/cpp/.traces/loop b/cpp/.traces/loop
index 4cfc2250..d68874c4 100644
--- a/cpp/.traces/loop
+++ b/cpp/.traces/loop
@@ -8,7 +8,7 @@ parse/0: label: {
 parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
 parse/0:   product: {name: "3", value: 0, type: 1, properties: ["3": "integer"]}
-parse/0: instruction: 33
+parse/0: instruction: 34
 parse/0: label: }
 brace/0: 1000: push (open, 2)
 brace/0: push (close, 5)
diff --git a/cpp/.traces/loop_nested b/cpp/.traces/loop_nested
index b707de42..37ccf23f 100644
--- a/cpp/.traces/loop_nested
+++ b/cpp/.traces/loop_nested
@@ -10,7 +10,7 @@ parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
 parse/0:   product: {name: "3", value: 0, type: 1, properties: ["3": "integer"]}
 parse/0: label: }
-parse/0: instruction: 34
+parse/0: instruction: 35
 parse/0:   ingredient: {name: "4", value: 0, type: 3, properties: ["4": "boolean"]}
 parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
diff --git a/cpp/.traces/loop_unless b/cpp/.traces/loop_unless
index fe50d87e..efd39cc2 100644
--- a/cpp/.traces/loop_unless
+++ b/cpp/.traces/loop_unless
@@ -5,7 +5,7 @@ parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
 parse/0:   product: {name: "2", value: 0, type: 1, properties: ["2": "integer"]}
 parse/0: label: {
-parse/0: instruction: 35
+parse/0: instruction: 36
 parse/0:   ingredient: {name: "2", value: 0, type: 1, properties: ["2": "integer"]}
 parse/0: instruction: 1
 parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
diff --git a/cpp/.traces/new b/cpp/.traces/new
index ff60abae..6b9fb9a9 100644
--- a/cpp/.traces/new
+++ b/cpp/.traces/new
@@ -1,7 +1,7 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "integer", value: 0, type: 0, properties: ["integer": "type"]}
 parse/0:   product: {name: "1", value: 0, type: 2-1, properties: ["1": "address":"integer", "raw": ]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "integer", value: 0, type: 0, properties: ["integer": "type"]}
 parse/0:   product: {name: "2", value: 0, type: 2-1, properties: ["2": "address":"integer", "raw": ]}
 parse/0: instruction: 13
diff --git a/cpp/.traces/new_array b/cpp/.traces/new_array
index 32a600fc..6f0fc8ac 100644
--- a/cpp/.traces/new_array
+++ b/cpp/.traces/new_array
@@ -1,8 +1,8 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "integer", value: 0, type: 0, properties: ["integer": "type"]}
 parse/0:   ingredient: {name: "5", value: 0, type: 0, properties: ["5": "literal"]}
 parse/0:   product: {name: "1", value: 0, type: 2-5-1, properties: ["1": "address":"array":"integer", "raw": ]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "integer", value: 0, type: 0, properties: ["integer": "type"]}
 parse/0:   product: {name: "2", value: 0, type: 2-1, properties: ["2": "address":"integer", "raw": ]}
 parse/0: instruction: 3
diff --git a/cpp/.traces/new_concurrent b/cpp/.traces/new_concurrent
index 5e35b113..94200129 100644
--- a/cpp/.traces/new_concurrent
+++ b/cpp/.traces/new_concurrent
@@ -1,9 +1,9 @@
 parse/0: instruction: 29
 parse/0:   ingredient: {name: "f2", value: 0, type: 0, properties: ["f2": "recipe"]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "integer", value: 0, type: 0, properties: ["integer": "type"]}
 parse/0:   product: {name: "1", value: 0, type: 2-1, properties: ["1": "address":"integer", "raw": ]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "integer", value: 0, type: 0, properties: ["integer": "type"]}
 parse/0:   product: {name: "2", value: 0, type: 2-1, properties: ["2": "address":"integer", "raw": ]}
 parse/0: instruction: 13
diff --git a/cpp/.traces/new_overflow b/cpp/.traces/new_overflow
index 6a24ab18..877f1f46 100644
--- a/cpp/.traces/new_overflow
+++ b/cpp/.traces/new_overflow
@@ -1,7 +1,7 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "integer", value: 0, type: 0, properties: ["integer": "type"]}
 parse/0:   product: {name: "1", value: 0, type: 2-1, properties: ["1": "address":"integer", "raw": ]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "point", value: 0, type: 0, properties: ["point": "type"]}
 parse/0:   product: {name: "2", value: 0, type: 2-6, properties: ["2": "address":"point", "raw": ]}
 new/0: integer -> 1
diff --git a/cpp/.traces/new_string b/cpp/.traces/new_string
index 6b6cf903..e38d328b 100644
--- a/cpp/.traces/new_string
+++ b/cpp/.traces/new_string
@@ -1,4 +1,4 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "abc def", value: 0, type: 0, properties: ["abc def": "literal-string"]}
 parse/0:   product: {name: "1", value: 0, type: 2-5-4, properties: ["1": "address":"array":"character"]}
 parse/0: instruction: 21
diff --git a/cpp/.traces/stalled_routine b/cpp/.traces/stalled_routine
new file mode 100644
index 00000000..cb2311c5
--- /dev/null
+++ b/cpp/.traces/stalled_routine
@@ -0,0 +1,40 @@
+parse/0: instruction: 1
+parse/0:   ingredient: {name: "0", value: 0, type: 0, properties: ["0": "literal"]}
+parse/0:   product: {name: "1", value: 0, type: 1, properties: ["1": "integer"]}
+parse/0: instruction: 29
+parse/0:   ingredient: {name: "f2", value: 0, type: 0, properties: ["f2": "recipe"]}
+parse/0: instruction: 30
+parse/0:   ingredient: {name: "1", value: 0, type: 1, properties: ["1": "integer"]}
+parse/0: instruction: 1
+parse/0:   ingredient: {name: "1", value: 0, type: 1, properties: ["1": "integer"]}
+parse/0:   product: {name: "2", value: 0, type: 1, properties: ["2": "integer"]}
+parse/0: instruction: 1
+parse/0:   ingredient: {name: "34", value: 0, type: 0, properties: ["34": "literal"]}
+parse/0:   product: {name: "1", value: 0, type: 1, properties: ["1": "integer"]}
+after-brace/0: recipe f1
+after-brace/0: copy ...
+after-brace/0: run ...
+after-brace/0: wait-for-location ...
+after-brace/0: copy ...
+after-brace/0: recipe f2
+after-brace/0: copy ...
+new/0: routine allocated memory from 1000 to 101000
+schedule/0: f1
+run/0: instruction f1/0
+run/0: ingredient 0 is 0
+mem/0: storing 0 in location 1
+run/0: instruction f1/1
+run/0: ingredient 0 is f2
+new/0: routine allocated memory from 101000 to 201000
+run/0: instruction f1/2
+run/0: waiting for 1 to change from 0
+schedule/0: f2
+run/0: instruction f2/0
+run/0: ingredient 0 is 34
+mem/0: storing 34 in location 1
+schedule/0: waking up routine
+schedule/0: f1
+run/0: instruction f1/3
+run/0: ingredient 0 is 1
+mem/0: location 1 is 34
+mem/0: storing 34 in location 2
diff --git a/cpp/.traces/string-append-1 b/cpp/.traces/string-append-1
index dbc84dcb..8dd9c849 100644
--- a/cpp/.traces/string-append-1
+++ b/cpp/.traces/string-append-1
@@ -1,7 +1,7 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "hello,", value: 0, type: 0, properties: ["hello,": "literal-string"]}
 parse/0:   product: {name: "1", value: 0, type: 2-5-4, properties: ["1": "address":"array":"character", "raw": ]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: " world!", value: 0, type: 0, properties: [" world!": "literal-string"]}
 parse/0:   product: {name: "2", value: 0, type: 2-5-4, properties: ["2": "address":"array":"character", "raw": ]}
 parse/0: instruction: 106
diff --git a/cpp/.traces/string-equal-common-lengths-but-distinct b/cpp/.traces/string-equal-common-lengths-but-distinct
index 45605a29..a21aaafe 100644
--- a/cpp/.traces/string-equal-common-lengths-but-distinct
+++ b/cpp/.traces/string-equal-common-lengths-but-distinct
@@ -1,11 +1,11 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "location", value: 0, type: 0, properties: ["location": "type"]}
 parse/0:   ingredient: {name: "30", value: 0, type: 0, properties: ["30": "literal"]}
 parse/0:   product: {name: "default-space", value: 0, type: 2-5-1, properties: ["default-space": "address":"array":"location"]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "abc", value: 0, type: 0, properties: ["abc": "literal-string"]}
 parse/0:   product: {name: "x", value: 0, type: 2-5-4, properties: ["x": "address":"array":"character"]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "abd", value: 0, type: 0, properties: ["abd": "literal-string"]}
 parse/0:   product: {name: "y", value: 0, type: 2-5-4, properties: ["y": "address":"array":"character"]}
 parse/0: instruction: 100
diff --git a/cpp/.traces/string-equal-distinct-lengths b/cpp/.traces/string-equal-distinct-lengths
index 249f6a32..e410fdc1 100644
--- a/cpp/.traces/string-equal-distinct-lengths
+++ b/cpp/.traces/string-equal-distinct-lengths
@@ -1,11 +1,11 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "location", value: 0, type: 0, properties: ["location": "type"]}
 parse/0:   ingredient: {name: "30", value: 0, type: 0, properties: ["30": "literal"]}
 parse/0:   product: {name: "default-space", value: 0, type: 2-5-1, properties: ["default-space": "address":"array":"location"]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "abc", value: 0, type: 0, properties: ["abc": "literal-string"]}
 parse/0:   product: {name: "x", value: 0, type: 2-5-4, properties: ["x": "address":"array":"character"]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "abcd", value: 0, type: 0, properties: ["abcd": "literal-string"]}
 parse/0:   product: {name: "y", value: 0, type: 2-5-4, properties: ["y": "address":"array":"character"]}
 parse/0: instruction: 100
diff --git a/cpp/.traces/string-equal-identical b/cpp/.traces/string-equal-identical
index bd621b78..cf783038 100644
--- a/cpp/.traces/string-equal-identical
+++ b/cpp/.traces/string-equal-identical
@@ -1,11 +1,11 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "location", value: 0, type: 0, properties: ["location": "type"]}
 parse/0:   ingredient: {name: "30", value: 0, type: 0, properties: ["30": "literal"]}
 parse/0:   product: {name: "default-space", value: 0, type: 2-5-1, properties: ["default-space": "address":"array":"location"]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "abc", value: 0, type: 0, properties: ["abc": "literal-string"]}
 parse/0:   product: {name: "x", value: 0, type: 2-5-4, properties: ["x": "address":"array":"character"]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "abc", value: 0, type: 0, properties: ["abc": "literal-string"]}
 parse/0:   product: {name: "y", value: 0, type: 2-5-4, properties: ["y": "address":"array":"character"]}
 parse/0: instruction: 100
diff --git a/cpp/.traces/string-equal-reflexive b/cpp/.traces/string-equal-reflexive
index b0379aee..6889bd9d 100644
--- a/cpp/.traces/string-equal-reflexive
+++ b/cpp/.traces/string-equal-reflexive
@@ -1,8 +1,8 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "location", value: 0, type: 0, properties: ["location": "type"]}
 parse/0:   ingredient: {name: "30", value: 0, type: 0, properties: ["30": "literal"]}
 parse/0:   product: {name: "default-space", value: 0, type: 2-5-1, properties: ["default-space": "address":"array":"location"]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "abc", value: 0, type: 0, properties: ["abc": "literal-string"]}
 parse/0:   product: {name: "x", value: 0, type: 2-5-4, properties: ["x": "address":"array":"character"]}
 parse/0: instruction: 100
diff --git a/cpp/.traces/string-equal-with-empty b/cpp/.traces/string-equal-with-empty
index f7c4fb88..c25963b3 100644
--- a/cpp/.traces/string-equal-with-empty
+++ b/cpp/.traces/string-equal-with-empty
@@ -1,11 +1,11 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "location", value: 0, type: 0, properties: ["location": "type"]}
 parse/0:   ingredient: {name: "30", value: 0, type: 0, properties: ["30": "literal"]}
 parse/0:   product: {name: "default-space", value: 0, type: 2-5-1, properties: ["default-space": "address":"array":"location"]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "", value: 0, type: 0, properties: ["": "literal-string"]}
 parse/0:   product: {name: "x", value: 0, type: 2-5-4, properties: ["x": "address":"array":"character"]}
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "abcd", value: 0, type: 0, properties: ["abcd": "literal-string"]}
 parse/0:   product: {name: "y", value: 0, type: 2-5-4, properties: ["y": "address":"array":"character"]}
 parse/0: instruction: 100
diff --git a/cpp/.traces/string_literal b/cpp/.traces/string_literal
index be063bc6..966b5166 100644
--- a/cpp/.traces/string_literal
+++ b/cpp/.traces/string_literal
@@ -1,3 +1,3 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "abc def", value: 0, type: 0, properties: ["abc def": "literal-string"]}
 parse/0:   product: {name: "1", value: 0, type: 2-5-4, properties: ["1": "address":"array":"character"]}
diff --git a/cpp/.traces/string_literal_nested b/cpp/.traces/string_literal_nested
index 3b22a0d6..963b8ad8 100644
--- a/cpp/.traces/string_literal_nested
+++ b/cpp/.traces/string_literal_nested
@@ -1,3 +1,3 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "abc [def]", value: 0, type: 0, properties: ["abc [def]": "literal-string"]}
 parse/0:   product: {name: "1", value: 0, type: 2-5-4, properties: ["1": "address":"array":"character"]}
diff --git a/cpp/.traces/string_literal_with_colons b/cpp/.traces/string_literal_with_colons
index 95200b73..a646ca0f 100644
--- a/cpp/.traces/string_literal_with_colons
+++ b/cpp/.traces/string_literal_with_colons
@@ -1,3 +1,3 @@
-parse/0: instruction: 36
+parse/0: instruction: 37
 parse/0:   ingredient: {name: "abc:def/ghi", value: 0, type: 0, properties: ["abc:def/ghi": "literal-string"]}
 parse/0:   product: {name: "1", value: 0, type: 2-5-4, properties: ["1": "address":"array":"character"]}
diff --git a/cpp/038scheduler.cc b/cpp/038scheduler.cc
index f0f970dd..76b90933 100644
--- a/cpp/038scheduler.cc
+++ b/cpp/038scheduler.cc
@@ -18,7 +18,7 @@ recipe f2 [
 void run_current_routine(size_t time_slice)
 :(replace "while (!Current_routine->completed())" following "void run_current_routine(size_t time_slice)")
 size_t ninstrs = 0;
-while (!Current_routine->completed() && ninstrs < time_slice)
+while (Current_routine->state == RUNNING && ninstrs < time_slice)
 :(after "Running One Instruction")
 ninstrs++;
 
@@ -28,7 +28,7 @@ ninstrs++;
 enum routine_state {
   RUNNING,
   COMPLETED,
-  // End Routine States
+  // End routine States
 };
 :(before "End routine Fields")
 enum routine_state state;
diff --git a/cpp/039wait.cc b/cpp/039wait.cc
new file mode 100644
index 00000000..eba3a437
--- /dev/null
+++ b/cpp/039wait.cc
@@ -0,0 +1,57 @@
+//: Routines can be put in a 'waiting' state, from which it will be ready to
+//: run again when a specific memory location changes its value. This is mu's
+//: basic technique for orchestrating the order in which different routines
+//: operate.
+
+:(scenario "stalled_routine")
+recipe f1 [
+  1:integer <- copy 0:literal
+  run f2:recipe
+  wait-for-location 1:integer
+  # now wait for f2 to run and modify location 1 before using its value
+  2:integer <- copy 1:integer
+]
+recipe f2 [
+  1:integer <- copy 34:literal
+]
+# if we got the synchronization wrong we'd be storing 0 in location 2
++mem: storing 34 in location 2
+
+//: define the new state that all routines can be in
+
+:(before "End routine States")
+WAITING,
+:(before "End routine Fields")
+// only if state == WAITING
+size_t waiting_on_location;
+int old_value_of_wating_location;
+:(before "End routine Constructor")
+waiting_on_location = old_value_of_wating_location = 0;
+
+//: primitive recipe to put routines in that state
+
+:(before "End Primitive Recipe Declarations")
+WAIT_FOR_LOCATION,
+:(before "End Primitive Recipe Numbers")
+Recipe_number["wait-for-location"] = WAIT_FOR_LOCATION;
+:(before "End Primitive Recipe Implementations")
+case WAIT_FOR_LOCATION: {
+  reagent loc = canonize(current_instruction().ingredients[0]);
+  Current_routine->state = WAITING;
+  Current_routine->waiting_on_location = loc.value;
+  Current_routine->old_value_of_wating_location = Memory[loc.value];
+  trace("run") << "waiting for " << loc.value << " to change from " << Memory[loc.value];
+  break;
+}
+
+//: scheduler tweak to get routines out of that state
+
+:(before "End Scheduler State Transitions")
+for (size_t i = 0; i < Routines.size(); ++i) {
+  if (Routines[i]->state != WAITING) continue;
+  if (Memory[Routines[i]->waiting_on_location] != Routines[i]->old_value_of_wating_location) {
+    trace("schedule") << "waking up routine\n";
+    Routines[i]->state = RUNNING;
+    Routines[i]->waiting_on_location = Routines[i]->old_value_of_wating_location = 0;
+  }
+}