83 lines
3.3 KiB
Scheme
83 lines
3.3 KiB
Scheme
(unit/sig extra-xexpr^
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(import xml-structs^ writer^ mzlib:function^)
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;; Xexpr ::= String
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;; | (list* Symbol (listof Attribute-srep) (listof Xexpr))
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;; | (cons Symbol (listof Xexpr))
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;; | Symbol
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;; | Nat
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;; | Comment
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;; | Processing-instruction
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;; Attribute-srep ::= (list Symbol String)
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;; sorting is no longer necessary, since xt3d uses xml->zxexpr, which sorts.
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;; assoc-sort : (listof (list Symbol a)) -> (listof (list Symbol a))
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(define (assoc-sort to-sort)
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(quicksort to-sort (bcompose string<? (compose symbol->string car))))
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(define xexpr-drop-empty-attributes (make-parameter #f))
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;; xml->xexpr : Content -> Xexpr
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;; The contract is loosely enforced.
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(define (xml->xexpr x)
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(let* ([non-dropping-combine
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(lambda (atts body)
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(cons (assoc-sort (map attribute->srep atts))
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body))]
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[combine (if (xexpr-drop-empty-attributes)
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(lambda (atts body)
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(if (null? atts)
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body
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(non-dropping-combine atts body)))
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non-dropping-combine)])
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(let loop ([x x])
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(cond
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[(element? x)
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(let ([body (map loop (element-content x))]
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[atts (element-attributes x)])
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(cons (element-name x) (combine atts body)))]
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[(pcdata? x) (pcdata-string x)]
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[(entity? x) (entity-text x)]
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[(or (comment? x) (pi? x)) x]
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[(document? x) (error 'xml->xexpr "Expected content, given ~a~nUse document-element to extract the content." x)]
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[else (error 'xml->xexpr "Expected content, given ~a" x)]))))
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;; attribute->srep : Attribute -> Attribute-srep
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(define (attribute->srep a)
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(list (attribute-name a) (attribute-value a)))
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;; srep->attribute : Attribute-srep -> Attribute
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(define (srep->attribute a)
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(unless (and (pair? a) (pair? (cdr a)) (null? (cddr a)) (symbol? (car a)) (string? (cadr a)))
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(error 'srep->attribute "expected (cons Symbol String) given ~a" a))
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(make-attribute 'scheme 'scheme (car a) (cadr a)))
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;; xexpr->xml : Xexpr -> Content
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;; The contract is enforced.
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(define (xexpr->xml x)
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(cond
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[(pair? x)
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(let ([f (lambda (atts body)
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(unless (list? body)
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(error 'xexpr->xml "expected a list of xexprs a the body in ~a" x))
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(make-element 'scheme 'scheme (car x)
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atts
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(map xexpr->xml body)))])
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(if (and (pair? (cdr x)) (or (null? (cadr x)) (and (pair? (cadr x)) (pair? (caadr x)))))
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(f (map srep->attribute (cadr x)) (cddr x))
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(f null (cdr x))))]
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[(string? x) (make-pcdata 'scheme 'scheme x)]
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[(or (symbol? x) (and (integer? x) (>= x 0))) (make-entity 'scheme 'scheme x)]
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[(or (comment? x) (pi? x)) x]
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[else (error 'xexpr->xml "malformed xexpr ~s" x)]))
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;; xexpr->string : Xexpression -> String
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(define (xexpr->string xexpr)
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(let ([port (open-output-string)])
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(write-xml/content (xexpr->xml xexpr) port)
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(get-output-string port)))
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;; bcompose : (a a -> c) (b -> a) -> (b b -> c)
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(define (bcompose f g)
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(lambda (x y) (f (g x) (g y)))))
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