Tom Willemse
c454bde37c
Write a small DSL for converting a simple lisp expression to an MPD query
format. This turns, for example:
(and (= artist "Katatonia") (= album "Last Fair Deal Gone Down"))
Into:
((artist == "Katatonia") AND (album == "Last Fair Deal Gone Down"))
The expressions inside ‘query’ are quasi-quoted, so that variable substitution
is possible.
22 lines
629 B
Scheme
22 lines
629 B
Scheme
(define-structure mpd (export query)
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(open scheme-with-scsh)
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(begin
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(define-syntax query
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(syntax-rules ()
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((_ a)
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(mpd-query-1 `a))))
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(define (mpd-query-equals params)
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(apply format #f "~s == ~s" params))
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(define (mpd-query-and params)
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(format #f "~a AND ~a"
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(mpd-query-1 (car params))
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(mpd-query-1 (cadr params))))
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(define (mpd-query-1 query)
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(format #f "(~a)"
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(let ((op (car query)))
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(case op
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('= (mpd-query-equals (cdr query)))
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('and (mpd-query-and (cdr query)))))))))
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