Update README

Add true/false

1 files changed, 43 insertions, 25 deletions

diff --git a/chapter05/README.md b/chapter05/README.md
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@@ -31,47 +31,65 @@ Here is a recap of the nodes introduced in previous chapters:
 
 Following new nodes are introduced in this chapter:
 
-| Node Name | Type    | Chapter | Description                                                          | Inputs                                                                                         | Value                                                         |
-|-----------|---------|---------|----------------------------------------------------------------------|------------------------------------------------------------------------------------------------|---------------------------------------------------------------|
-| If        | Control | 5       | Represents an `if` condition, sub type of `MultiNode`                | A control node and a data predicate node                                                       | A tuple of two values, one for true branch, another for false |
-| Region    | Control | 5       | Represents a merge point from multiple control flow                  | An input for each control flow that is merging                                                 | Merged control                                                |
-| Phi       | Data    | 5       | Represents the phi function that picks a value based on control flow | A region control node, and multiple data nodes that provide values from multiple control flows | Result is the extracted value depending on control flow taken | 
-| Stop      | Control | 5       | Represents termination of the program                                | One or more Return nodes                                                                       | None                                                          |
+| Node Name | Type    | Chapter | Description                                        | Inputs                                         | Value                                              |
+|-----------|---------|---------|----------------------------------------------------|------------------------------------------------|----------------------------------------------------|
+| If        | Control | 5       | A branching test, sub type of `MultiNode`          | A control node and a data predicate node       | A tuple of two values: one for true, one for false |
+| Region    | Control | 5       | A merge point for multiple control flow            | An input for each control flow that is merging | Merged control                                     |
+| Phi       | Data    | 5       | A phi function picks a value based on control flow | A Region, and data nodes for each control path | Depends on control flow path taken                 | 
+| Stop      | Control | 5       | Termination of the program                         | One or more Return nodes                       | None                                               |
 
 ## `If` Nodes
 
-`If` node takes in both control and data (predicate expression) and routes the control token to one of the two control flows, represented by the `Proj` nodes.
+`If` node takes in both control and data (predicate expression) and routes the
+control token to one of the two control flows, represented by true and false
+`Proj` nodes.
 
 ## `Phi` Nodes
 
-The `Phi` reads in both data and control, and outputs a data value. The control input to the `Phi` points to a `Region` node. The data inputs to the `Phi` are one each for the control inputs to that `Region`.
-The result computed by a `Phi` depends both on the data and the matching control input. At most one control input to the `Region` can be active at a time. The `Phi` passes through the data value from the matching input [[1]](#1).
+A `Phi` reads in both data and control, and outputs a data value.  The control
+input to the `Phi` points to a `Region` node.  The data inputs to the `Phi` are
+one each for the control inputs to that `Region`.  The result computed by a
+`Phi` depends both on the data and the matching control input.  At most one
+control input to the `Region` can be active at a time, and the `Phi` passes
+through the data value from the matching input [[1]](#1).
 
 ## `Region` Nodes
 
-`Region` nodes were originally introduced to replace Basic Blocks in the IR [[3]](#3). However, we do not assign a `Region` to every node in the graph; we insert a `Region` node at a merge point where it takes control from each predecessor control edge, and produces 
-a merged control as output. Data flows via `Phi` nodes at these merge points.
+`Region` nodes were originally introduced to replace Basic Blocks in the IR
+[[3]](#3).  However, we do not assign a `Region` to every node in the graph; we
+insert a `Region` node at a merge point where it takes control from each
+predecessor control edge, and produces a merged control as output.  Data flows
+via `Phi` nodes at these merge points.
 
 ## Parsing of `If` statement
 
-When we parse an `if` statement, the control flow splits at that point. We must track the names being updated in each part of the `if` statement, and then merge them at the end.
-The implementation follows the description in [[2]](#2).
+When we parse an `if` statement, the control flow splits at that point.  We
+must track the names being updated in each part of the `if` statement, and then
+merge them at the end.  The implementation follows the description in
+[[2]](#2).
 
 This involves following:
 
-* We create an `IfNode` with the current control token, i.e. the node mapped to `$ctrl`, and the `if` predicate expression as inputs.
-* We add two `ProjNodes` - one for the `True` branch (call if `ifT`), and the other for the `False` branch (call it `ifF`) - these extract values from the tuple result of the `IfNode`.
-* We duplicate the current `ScopeNode`. The duplicated `ScopeNode` contains all the stack levels as the original, and moreover the new node is added as a user of all the names that are currently bound.
-* The original `ScopeNode` is saved.
-* We set the duplicate `ScopeNode` as current.
-* We set control token to the `True` projection node `ifT`.
-* We parse the true branch of the `if` statement.
-* We reset the original `ScopeNode` as current.
-* We set control token to the `False` projection node `ifF`.
-* If there is an `else` statement we parse it.
-* At this point we have two `ScopeNode`s; the original one, potentially updated by the `False` branch, and the duplicate one, potentially updated by the `True` branch.
+* We create an `IfNode` with the current control token, i.e. the node mapped to
+  `$ctrl`, and the `if` predicate expression as inputs.
+* We add two `ProjNodes` - one for the `True` branch (call if `ifT`), and the
+  other for the `False` branch (call it `ifF`) - these extract values from the
+  tuple result of the `IfNode`.
+* We duplicate the current `ScopeNode`.  The duplicated `ScopeNode` contains
+  all the same symbol tables as the original, and has the same edges.
+* We set control token to the `True` projection node `ifT`, and parse the true
+  branch of the `if` statement.
+* We reset the dupped `ScopeNode` as current.
+* We set control token to the `False` projection node `ifF`, and if there is an
+  `else` statement we parse it.
+* At this point we have two `ScopeNode`s; the original one, potentially updated
+  by the `True` branch, and the duplicate one, potentially updated by the
+  `False` branch.  
 * We create a `Region` node to represent a merge point.
-* We compare the two `ScopeNode`s. We create `Phi` nodes for any names whose bindings differ. The `Phi` nodes take the `Region` node as the control input and the two data nodes from each of the `ScopeNode`s. The name binding is updated to point to the `Phi` node.
+* We *merge* the two `ScopeNode`s. We create `Phi` nodes for any names whose
+  bindings differ.  The `Phi` nodes take the `Region` node as the control input
+  and the two data nodes from each of the `ScopeNode`s.  The name binding is
+  updated to point to the `Phi` node.
 * Finally, we set the `Region` node as the control token, and discard the duplicated `ScopeNode`.
 
 ## Example