ref: 74d4de6ad5bcac532631d8dfb82d9e6c0435fc0f
dir: /attic/scrap.lsp/
; -*- scheme -*-
; (try expr
; (catch (type-error e) . exprs)
; (catch (io-error e) . exprs)
; (catch (e) . exprs)
; (finally . exprs))
(define-macro (try expr . forms)
(let* ((e (gensym))
(reraised (gensym))
(final (f-body (cdr (or (assq 'finally forms) '(())))))
(catches (filter (lambda (f) (eq (car f) 'catch)) forms))
(catchblock `(cond
,.(map (lambda (catc)
(let* ((specific (cdr (cadr catc)))
(extype (caadr catc))
(var (if specific (car specific)
extype))
(todo (cddr catc)))
`(,(if specific
; exception matching logic
`(or (eq ,e ',extype)
(and (pair? ,e)
(eq (car ,e)
',extype)))
#t); (catch (e) ...), match anything
(let ((,var ,e)) (begin ,@todo)))))
catches)
(#t (raise ,e))))) ; no matches, reraise
(if final
(if catches
; form with both catch and finally
`(prog1 (trycatch ,expr
(lambda (,e)
(trycatch ,catchblock
(lambda (,reraised)
(begin ,final
(raise ,reraised))))))
,final)
; finally only; same as unwind-protect
`(prog1 (trycatch ,expr (lambda (,e)
(begin ,final (raise ,e))))
,final))
; catch, no finally
`(trycatch ,expr (lambda (,e) ,catchblock)))))
; setf
; expands (setf (place x ...) v) to (mutator (f x ...) v)
; (mutator (identity x ...) v) is interpreted as (mutator x ... v)
(set! *setf-place-list*
; place mutator f
'((car rplaca identity)
(cdr rplacd identity)
(caar rplaca car)
(cadr rplaca cdr)
(cdar rplacd car)
(cddr rplacd cdr)
(caaar rplaca caar)
(caadr rplaca cadr)
(cadar rplaca cdar)
(caddr rplaca cddr)
(cdaar rplacd caar)
(cdadr rplacd cadr)
(cddar rplacd cdar)
(cdddr rplacd cddr)
(list-ref rplaca nthcdr)
(get put! identity)
(aref aset! identity)
(symbol-syntax set-syntax! identity)))
(define (setf-place-mutator place val)
(if (symbol? place)
(list 'set! place val)
(let ((mutator (assq (car place) *setf-place-list*)))
(if (null? mutator)
(error "setf: unknown place " (car place))
(if (eq (caddr mutator) 'identity)
(cons (cadr mutator) (append (cdr place) (list val)))
(list (cadr mutator)
(cons (caddr mutator) (cdr place))
val))))))
(define-macro (setf . args)
(f-body
((label setf-
(lambda (args)
(if (null? args)
()
(cons (setf-place-mutator (car args) (cadr args))
(setf- (cddr args))))))
args)))
(define-macro (labels binds . body)
(cons (list 'lambda (map car binds)
(f-body
(nconc (map (lambda (b)
(list 'set! (car b) (cons 'lambda (cdr b))))
binds)
body)))
(map (lambda (x) #f) binds)))
(define (evalhead e env)
(if (and (symbol? e)
(or (constant? e)
(and (not (memq e env))
(bound? e)
(builtin? (eval e)))))
(eval e)
e))