CQCL · acl-cqc · Oct 16, 2023 · Sep 27, 2023 · Sep 28, 2023 · Oct 10, 2023
@@ -369,13 +369,15 @@ flowchart
 
 ##### `TailLoop` nodes
 
-These provide tail-controlled loops: the data sibling graph within the
-TailLoop-node computes a value of 2-ary `Predicate(#i, #o)`; the first
-variant means to repeat the loop with the values of the tuple unpacked
-and “fed” in at at the top; the second variant means to exit the loop
-with those values unpacked. The graph may additionally take in a row
-`#x` (appended to `#i`) and return the same row (appended to `#o`). The
-contained graph may thus be evaluated more than once.
+These provide tail-controlled loops: the dataflow sibling graph within the
+TailLoop-node computes a value of 2-ary `Predicate(#i, #o)`, as well as
+a row `#x` of other values (perhaps empty). The first variant means to
+repeat the loop with the computed values fed in at the top of the DSG,
+which has inputs `#i,#x`; the second variant means to exit the loop
+and output `#o,#x` from the TailLoop node. (In both cases the tuple
+within the Predicate is unpacked.) Thus, the contained graph may be
+evaluated more than once, with the first iteration using the inputs
+to the TailLoop node: `#i,#x`.
-These provide tail-controlled loops: the dataflow sibling graph within the
-TailLoop-node computes a value of 2-ary `Predicate(#i, #o)`, as well as
-a row `#x` of other values (perhaps empty). The first variant means to
-repeat the loop with the computed values fed in at the top of the DSG,
-which has inputs `#i,#x`; the second variant means to exit the loop
-and output `#o,#x` from the TailLoop node. (In both cases the tuple
-within the Predicate is unpacked.) Thus, the contained graph may be
-evaluated more than once, with the first iteration using the inputs
-to the TailLoop node: `#i,#x`.
+These provide tail-controlled loops. The node has a `FunctionType`
+```
+#I:#X -> #O:#X
+```
+where `#I, #O, #X` are rows and `:` expresses row concatenation.
+
+Correspondingly, the dataflow sibling graph inside the TailLoop-node has `FunctionType`
+```
+#I :#X -> (Predicate(#I, #O)):#X
+```
+
+The `Predicate` type variants signal loop continuation or termination.
+The first variant means to
+repeat the loop with the computed values (`#I:#X`) fed in at the top of the DSG;
+the second variant means to exit the loop
+and output `#O:#X` from the TailLoop node. (In both cases the tuple
+within the Predicate is unpacked.) Thus, the contained graph may be
+evaluated more than once, with the first iteration using the inputs
+to the TailLoop node.
-These provide tail-controlled loops: the dataflow sibling graph within the
-TailLoop-node computes a value of 2-ary `Predicate(#i, #o)`, as well as
-a row `#x` of other values (perhaps empty). The first variant means to
-repeat the loop with the computed values fed in at the top of the DSG,
-which has inputs `#i,#x`; the second variant means to exit the loop
-and output `#o,#x` from the TailLoop node. (In both cases the tuple
-within the Predicate is unpacked.) Thus, the contained graph may be
-evaluated more than once, with the first iteration using the inputs
-to the TailLoop node: `#i,#x`.
+These provide tail-controlled loops. The node has a `FunctionType`
+```
+#I:#X -> #O:#X
+```
+where `#I, #O, #X` are rows and `:` expresses row concatenation.
+
+Correspondingly, the dataflow sibling graph inside the TailLoop-node has `FunctionType`
+```
+#I :#X -> (Predicate(#I, #O)):#X
+```
+
+The `Predicate` type variants signal loop continuation or termination.
+The first variant means to
+repeat the loop with the computed values (`#I:#X`) fed in at the top of the DSG;
+the second variant means to exit the loop
+and output `#O:#X` from the TailLoop node. (In both cases the tuple
+within the Predicate is unpacked.) Thus, the contained graph may be
+evaluated more than once, with the first iteration using the inputs
+to the TailLoop node.
 
 ##### Control Flow Graphs