;*=====================================================================*/
;*    serrano/prgm/project/skribe/doc/user/syntax.skb                  */
;*    -------------------------------------------------------------    */
;*    Author      :  Manuel Serrano                                    */
;*    Creation    :  Fri Nov 30 11:55:24 2001                          */
;*    Last change :  Sun Feb 29 16:14:53 2004 (eg)                     */
;*    Copyright   :  2001-04 Manuel Serrano                            */
;*    -------------------------------------------------------------    */
;*    The syntax of Skribe                                             */
;*=====================================================================*/

;*---------------------------------------------------------------------*/
;*    The Skribe syntax                                                */
;*---------------------------------------------------------------------*/
(chapter :title "Syntax & Values" [
A Skribe document is composed of Skribe expressions. A Skribe expression
can be:

,(itemize (item [An atomic expression, such as a string of characters, a number.])
	  (item [A list.])
	  (item [A text.]))

Here are several examples of correct Skribe expressions:

,(center (frame :margin 5 :border 0 :width *prgm-width*
		(color :margin 5 :bg *disp-color* :width 100.
(itemize (item [,(color :fg "#009900" (tt "\"foo\"")), a string of characters composed of the
characters `,(color :fg "#009900" "f")', `,(color :fg "#009900" "o")'
and `,(color :fg "#009900" "o")'.])
	 (item [,(color :fg "#009900" (tt "123") " " (tt "3.14")), two numbers.])
	 (item [,(color :fg "#009900" (tt "#t") " " (tt "#f")), the ,(emph "true") and ,(emph "false")
Skribe value.])
	 (item [,(color :fg "#009900" (tt "(bold \"foo bar\")")), a list.])
	 (item [,(color :fg "#009900" (tt (char 91)"A text sample"(char 93))), a simple text containing
three words and no escape sequence.])
	 (item [,(color :fg "#009900" (tt (char 91)"Another text sample (that is still) simple"(char 93))),
another simple text.])
	 (item [,(color :fg "#009900" (tt (char 91)"Another ,(bold \"text\") sample"(char 93))),
a more complex text that contains two words (,(color :fg "#009900" (tt "Another")) and ,(color :fg "#009900" (tt "sample")))
and an expression ,(color :fg "#009900" (tt "(bold \"text\")")). The escape sequence is introduced
with the `,(color :fg "#009900" (tt ",("))' characters.])))))

,(p [
Expressions are evaluated, thus ,(color :fg "#009900" (tt "(bold \"foo\")"))
has the effect of typesetting the word ,(color :fg "#009900" (tt "foo")) in
bold face to produce ,(color :fg "#009999" (bold "foo")). Escape sequences
enable evaluation of expressions inside the text. Thus the text
,(color :fg "#009900" (tt (char 91)"Another ,(bold \"text\") sample"(char 93)))
produces `,(color :fg "#009999" (tt [Another ,(bold "text") sample]))'.
On the other hand
,(color :fg "#009900" (tt (char 91)"Another (bold \"text\") sample"(char 93)))
produces
`,(color :fg "#009999" (tt [Another (bold "text") sample]))' because it does not contain
the escape sequence `,(color :fg "#009900" (char #\,)(char #\())'.])
]

;*---------------------------------------------------------------------*/
;*    Formal syntax                                                    */
;*---------------------------------------------------------------------*/
(section :title "Skribe syntax" 

(disp :verb #t :bg *prgm-skribe-color* [
<expr>    --> <atom>
            | <text>
            | <list>
<list>    --> (<expr>+)
<text>    --> ,(bold (color :fg "red" (char 91))),(it "any sequence but `,(' or a `,")<list>,(it "'"),(bold (color :fg "red" (char 93)))
<atom>    --> <boolean>
            | <integer>
            | <float>
            | <string>
            | <color>
<integer> --> ,(tt (char 91))0-9,(tt (char 93))+
<float>   --> ,(tt (char 91))0-9,(tt (char 93))+.,(tt (char 91))0-9,(tt (char 93))*
            | ,(tt (char 91))0-9,(tt (char 93))*.,(tt (char 91))0-9,(tt (char 93))+
<string>  --> ,(tt #\")...,(tt #\")
<color>   --> <string>
            | ,(tt #\")#,(tt (char 91))0-9a-f,(tt (char 93)),(tt (char 91))0-9a-f,(tt (char 93)),(tt (char 91))0-9a-f,(tt (char 93)),(tt (char 91))0-9a-f,(tt (char 93)),(tt (char 91))0-9a-f,(tt (char 93)),(tt (char 91))0-9a-f,(tt (char 93)),(tt #\")]))

;*---------------------------------------------------------------------*/
;*    Values                                                           */
;*---------------------------------------------------------------------*/
(section :title "Values" :file #f :toc #t 

;*--- width -----------------------------------------------------------*/
(subsection :title "Width" (p [
,(mark "width")
A Skribe ,(emph "width") refers to the horizontal size a construction
occupies on an output document. There are three different ways for
specifying a width:])

(description (item :key "An absolute pixel size" 
		  [This is represented by an ,(emph "exact") integer value
                  (such as ,(code "350")).])
	    (item :key "A relative size" 
		  [This is represented by an ,(emph "inexact") integer value
                  (such as ,(code "50.0")) which ranges in the interval 
                  ,(char 91)-100.0 .. 100.0,(char 93)])
	    (item :key "An engine dependent representation" 
		  [This is represented by a string that is directly emitted
                  in the output document (such as HTML column ,(code "\"0*\"")
                  specification). Note that this way of specifying width
                  is strictly unportable.])))))