Cheatsheets for pexprs

README.md

@@ -73,6 +73,7 @@ automatic, perfect-fidelity conversion between syntaxes.
 
 ## Additional resources
 
+ - [Preserves Expressions (P-expressions, pexprs)](preserves-expressions.html)
  - Some [conventions for common data types](conventions.html)
  - [Open questions](questions.html); see also the
    [issues list]({{page.projectpages}}/issues)

_includes/cheatsheet-pexprs-plaintext.md

@@ -1,22 +1,21 @@
-The definition of `Atom` is as given in the Preserves text syntax.
+The definitions of `Atom`, `ws`, and `linecomment` are as given in the Preserves text syntax.
 
 ```text
-Document      :=  Expr* sp
-Expr          :=  sp (Atom | Compound | Punct | Embedded | Annotated)
+Document      :=  Expr* ws
+Expr          :=  ws (SimpleExpr | Punct)
+SimpleExpr    :=  Atom | Compound | Embedded | Annotated
 Compound      :=  Sequence | Record | Block | Group | Set
 Punct         :=  `,` | `;` | `:`+
 
-sp            :=  (space | tab | cr | lf)*
-
-Sequence      :=   `[` Expr* Trailer sp `]`
-Record        :=   `<` Expr* Trailer sp `>`
-Block         :=   `{` Expr* Trailer sp `}`
-Group         :=   `(` Expr* Trailer sp `)`
-Set           :=  `#{` Expr* Trailer sp `}`
+Sequence      :=   `[` Expr* Trailer ws `]`
+Record        :=   `<` Expr* Trailer ws `>`
+Block         :=   `{` Expr* Trailer ws `}`
+Group         :=   `(` Expr* Trailer ws `)`
+Set           :=  `#{` Expr* Trailer ws `}`
 
 Trailer       :=  Annotation*
 
-Embedded      :=  `#!` Expr
-Annotated     :=  Annotation Expr
-Annotation    :=  `@` Expr | `#` ((space | tab) linecomment) (cr | lf)
+Embedded      :=  `#!` SimpleExpr
+Annotated     :=  Annotation SimpleExpr
+Annotation    :=  `@` SimpleExpr | `#` ((space | tab) linecomment) (cr | lf)
 ```

_includes/cheatsheet-pexprs.md

@@ -0,0 +1,23 @@
+The definitions of `Atom`, `ws`, and `linecomment` are as given in the Preserves text syntax.
+
+{:.postcard-grammar.textsyntax}
+| *Document*      | := |  *Expr*<sup>⋆</sup> **ws**
+| *Expr*          | := |  **ws** (*SimpleExpr* &#124; *Punct*)
+| *SimpleExpr*    | := |  *Atom* &#124; *Compound* &#124; *Embedded* &#124; *Annotated*
+| *Compound*      | := |  *Sequence* &#124; *Record* &#124; *Block* &#124; *Group* &#124; *Set*
+| *Punct*         | := |  `,` &#124; `;` &#124; `:`<sup>+</sup>
+
+{:.postcard-grammar.textsyntax}
+| *Sequence*      | := |   `[` *Expr*<sup>⋆</sup> *Trailer* **ws** `]`
+| *Record*        | := |   `<` *Expr*<sup>⋆</sup> *Trailer* **ws** `>`
+| *Block*         | := |   `{` *Expr*<sup>⋆</sup> *Trailer* **ws** `}`
+| *Group*         | := |   `(` *Expr*<sup>⋆</sup> *Trailer* **ws** `)`
+| *Set*           | := |  `#{` *Expr*<sup>⋆</sup> *Trailer* **ws** `}`
+
+{:.postcard-grammar.textsyntax}
+| *Trailer*       | := |  *Annotation*<sup>⋆</sup>
+
+{:.postcard-grammar.textsyntax}
+| *Embedded*      | := |  `#!` *SimpleExpr*
+| *Annotated*     | := |  *Annotation* *SimpleExpr*
+| *Annotation*    | := |  `@` *SimpleExpr* &#124; `#` ((**space** &#124; **tab**) *linecomment*) (**cr** &#124; **lf**)

cheatsheet-plaintext.md

@@ -6,6 +6,20 @@ title: "Preserves Quick Reference (Plaintext)"
 Tony Garnock-Jones <tonyg@leastfixedpoint.com>  
 {{ site.version_date }}. Version {{ site.version }}.
 
+These are non-normative "reference card" definitions. See also the normative [semantics]({{
+site.baseurl }}/preserves.html), [text syntax specification]({{ site.baseurl
+}}/preserves-text.html), and [machine-oriented syntax specification]({{ site.baseurl
+}}/preserves-binary.html), and the experimental [P-expressions definition]({{ site.baseurl
+}}/preserves-expressions.html).
+
+## <a id="binary"></a>Machine-Oriented Binary Syntax
+
 {% include cheatsheet-binary-plaintext.md %}
 
+## <a id="text"></a>Human-Oriented Text Syntax
+
 {% include cheatsheet-text-plaintext.md %}
+
+## <a id="pexprs"></a>P-expression Syntax
+
+{% include cheatsheet-pexprs-plaintext.md %}

cheatsheet.md

@@ -8,8 +8,9 @@ Tony Garnock-Jones <tonyg@leastfixedpoint.com>
 
 These are non-normative "reference card" definitions. See also the normative [semantics]({{
 site.baseurl }}/preserves.html), [text syntax specification]({{ site.baseurl
-}}/preserves-text.html) and [machine-oriented syntax specification]({{ site.baseurl
-}}/preserves-binary.html).
+}}/preserves-text.html), and [machine-oriented syntax specification]({{ site.baseurl
+}}/preserves-binary.html), and the experimental [P-expressions definition]({{ site.baseurl
+}}/preserves-expressions.html).
 
 ## <a id="binary"></a>Machine-Oriented Binary Syntax
 
@@ -18,3 +19,7 @@ site.baseurl }}/preserves.html), [text syntax specification]({{ site.baseurl
 ## <a id="text"></a>Human-Oriented Text Syntax
 
 {% include cheatsheet-text.md %}
+
+## <a id="pexprs"></a>P-expression Syntax
+
+{% include cheatsheet-pexprs.md %}

preserves-expressions.md

@@ -7,6 +7,7 @@ October 2023. Version 0.3.0.
 
 [text syntax]: preserves-text.html
 
+**Experimental.**
 This document defines a grammar called *Preserves Expressions*
 (*P-expressions*, *pexprs*) that includes [ordinary Preserves text
 syntax][text syntax] but offers extensions sufficient to support a Lisp-
@@ -49,8 +50,8 @@ a compound expression, special punctuation, an `Embedded` expression, or
 an `Annotated` expression. The class `SimpleExpr` includes all of `Expr`
 except special punctuation.
 
-              Expr = ws (SimpleExpr | Punct)
-        SimpleExpr = Atom | Compound | Embedded | Annotated
+              Expr = ws (SimpleExpr / Punct)
+        SimpleExpr = Atom / Compound / Embedded / Annotated
 
 Embedded and annotated values are as in the text syntax, differing only
 in that uses of `Value` are replaced with `SimpleExpr`.
@@ -58,6 +59,7 @@ in that uses of `Value` are replaced with `SimpleExpr`.
            Embedded = "#!" SimpleExpr
           Annotated = Annotation SimpleExpr
          Annotation = "@" SimpleExpr / "#" [(%x20 / %x09) linecomment] (CR / LF)
+        linecomment = *<any unicode scalar value except CR or LF>
 
 P-expression special punctuation marks are comma, semicolon, and sequences of one or more colons.