e makes sense in many places, B should join the party in structural

1 files changed, 25 insertions, 25 deletions

diff --git a/rprt.md b/rprt.md
index e34e9cf..5f45ef1 100644
--- a/rprt.md
+++ b/rprt.md
@@ -27,7 +27,7 @@ Selection functions produce Selection outputs and take zero (nullary functions),
 
 ## 2.1 Core Selection Functions
 
-There are ten core selection functions in RPRT. Seven have nullary and monadic forms. Two (`e`, `B`) have nullary form only. The function `-` additionally has dyadic semantics---it is the only selection function that may take two arguments.
+There are ten core selection functions in RPRT. All ten have nullary and monadic forms, while the function `-` additionally has dyadic semantics---it is the only selection function that may take two arguments.
 
 | Function   | Nullary semantics                                          | Output rank |
 |------------|------------------------------------------------------------|-------------|
@@ -43,19 +43,17 @@ There are ten core selection functions in RPRT. Seven have nullary and monadic f
 
 In the monadic case, all defined functions are rank preserving. Their action on ranks > 1 are given by broadcasting, that is, `α F` where `α` has rank 2 is computed by applying `F` to each rank 1 range in `α` and collecting the results into a list of ranges, mutatis mutandis for rank 3.
 
-**Note:** The functions `eB` have no monadic or dyadic forms. To use them as such is an error condition.
-
-**Note:** When the input has rank 0 (position), all defined monadic functions are the identity since positions have no internal structure within which to search or operate.
-
-| Function  | Semantics for rank 1 `α` |
-|-----------|--------------------------|
-| `α /re/`  | First re within `α`      |
-| `α x/re/` | All re within`α`         |
-| `α $`     | End position of`α`       |
-| `α #n`    | Char n within`α`         |
-| `α n`     | Line n within`α`         |
-| `α +n`    | Line n within`α`         |
-| `α -`     | Identity                 |
+| Function  | Semantics for rank 0 `α`         | Semantics for rank 1 `α`                 |
+|-----------|----------------------------------|------------------------------------------|
+| `α e`     | Empty selection (rank 2)         | Empty selection (rank 2)                 |
+| `α $`     | `α`                              | End position of `α`                      |
+| `α #n`    | `α`                              | Char n within `α`                        |
+| `α n`     | `α`                              | Line n within `α`                        |
+| `α /re/`  | `α`                              | First re within `α`                      |
+| `α x/re/` | `α`                              | All re within `α`                        |
+| `α +n`    | `α`                              | Line n within `α`                        |
+| `α B/re/` | Buffer matches `re`? `α` : empty | buffer matches `re`? `α` : empty         |
+| `α -`     | Range from `α` to end of buffer  | Range from start of `α` to end of buffer |
 
 The span function `-` is the only selection function with dyadic semantics. It creates ranges by spanning from one selection to another.
 
@@ -81,10 +79,11 @@ Operators take functions as arguments and return new functions.
 
 The reverse operator `'` takes a selection function and reverses its direction.
 
-**Note:** `'F` is not defined when `F` is one of the functions `e-B` .
+**Note:** `'F` is not defined when `F` is one of the functions `B-` .
 
 | Function | Nullary                        | Rank |
 |----------|--------------------------------|------|
+| `'e`     | synonymous with `e`            | 2    |
 | `'$`     | Start of buffer (position 0)   | 0    |
 | `'#n`    | Character n from end of buffer | 0    |
 | `'n`     | Line n from end of buffer      | 1    |
@@ -94,16 +93,16 @@ The reverse operator `'` takes a selection function and reverses its direction.
 
 In the monadic case, all functions are rank preserving, and all of the above functions are the identity on rank 0 inputs. Their action on ranks > 1 is by broadcasting.
 
-| Function   | Semantics for rank 1 `α`         |
-|------------|----------------------------------|
-| `α '$`     | Start position of `α`            |
-| `α '#n`    | Char n from end of `α`           |
-| `α 'n`     | Line n from end of `α`           |
-| `α '/re/`  | First match backward within `α`  |
-| `α 'x/re/` | All matches right-to-left in `α` |
-| `α '+n`    | Line -n within `α`               |
+| Function   | Semantics for rank 0 `α` | Semantics for rank 1 `α`         |
+|------------|--------------------------|----------------------------------|
+| `α 'e`     | Empty selection (rank 2) | Empty selection (rank 2)         |
+| `α '$`     | `α`                      | Start position of `α`            |
+| `α '#n`    | `α`                      | Char n from end of `α`           |
+| `α 'n`     | `α`                      | Line n from end of `α`           |
+| `α '/re/`  | `α`                      | First match backward within `α`  |
+| `α 'x/re/` | `α`                      | All matches right-to-left in `α` |
+| `α '+n`    | `α`                      | Line -n within `α`               |
 
-**Note:** When the input has rank 0 (position), all defined reversed monadic functions are the identity since positions have no internal structure within which to search or operate.
 
 ### 2.2.2 The Sequential Operator `;`
 
@@ -111,10 +110,11 @@ The sequential operator `;` transforms a selection function from operating "with
 
 **Note:** It is erroneous to use `;F` in the nullary case. TODO: or are there interesting semantics?
 
-**Note:** `;F` is not defined when `F` is one of `e-B` .
+**Note:** `;F` is not defined when `F` is one of `B-` .
 
 | Function   | Semantics for rank 0 `α`     | Semantics for rank 1 `α`            |
 |------------|------------------------------|-------------------------------------|
+| `α ;e`     | Empty selection (rank 2)     | Empty selection (rank 2)            |
 | `α ;$`     | End of buffer                | End of buffer (ignores `α`)         |
 | `α ;#n`    | Character n after `α`        | Character n after end of `α`        |
 | `α ;n`     | Line n after `α`             | Line n after end of `α`             |