records: match-record: Support thunked and delayed fields.
* guix/records.scm (match-record): Unwrap matched thunked and delayed fields.
* tests/records.scm ("match-record, thunked field",
"match-record, delayed field"): New tests.
Signed-off-by: Josselin Poiret <dev@jpoiret.xyz>
master
(unmatched-parenthesis d
Josselin Poiret
parent
1a4aace3af
commit
b88e38d4b5
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@ -21,6 +21,7 @@
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#:use-module (srfi srfi-1)
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#:use-module (srfi srfi-9)
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#:use-module (srfi srfi-26)
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#:use-module (srfi srfi-71)
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#:use-module (ice-9 match)
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#:use-module (ice-9 rdelim)
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#:autoload (system base target) (target-most-positive-fixnum)
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@ -432,6 +433,15 @@ inherited."
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(cookie (compute-abi-cookie field-spec)))
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(with-syntax (((field-spec* ...)
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(map field-spec->srfi-9 field-spec))
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((field-type ...)
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(map (match-lambda
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((? thunked-field?)
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(datum->syntax s 'thunked))
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((? delayed-field?)
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(datum->syntax s 'delayed))
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(else
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(datum->syntax s 'normal)))
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field-spec))
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((thunked-field-accessor ...)
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(filter-map (lambda (field)
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(and (thunked-field? field)
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@ -465,7 +475,7 @@ inherited."
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macro-expansion time."
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(syntax-case s (map-fields)
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((_ (map-fields _ _) macro)
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#'(macro (field ...)))
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#'(macro ((field field-type) ...)))
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(id
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(identifier? #'id)
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#'#,(rtd-identifier #'type)))))
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@ -578,30 +588,41 @@ pairs. Stop upon an empty line (after consuming it) or EOF."
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;;; Pattern matching.
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;;;
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(define-syntax lookup-field
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(define-syntax lookup-field+wrapper
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(lambda (s)
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"Look up FIELD in the given list and return an expression that represents
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its offset in the record. Raise a syntax violation when the field is not
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found."
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(syntax-case s ()
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((_ field offset ())
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(syntax-violation 'lookup-field "unknown record type field"
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"Look up FIELD in the given list and return both an expression that represents
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its offset in the record and a procedure that wraps it to return its \"true\" value
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(for instance, FORCE is returned in the case of a delayed field). RECORD is passed
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to thunked values. Raise a syntax violation when the field is not found."
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(syntax-case s (normal delayed thunked)
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((_ record field offset ())
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(syntax-violation 'match-record
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"unknown record type field"
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s #'field))
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((_ field offset (head tail ...))
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((_ record field offset ((head normal) tail ...))
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(free-identifier=? #'field #'head)
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#'offset)
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((_ field offset (_ tail ...))
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#'(lookup-field field (+ 1 offset) (tail ...))))))
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#'(values offset identity))
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((_ record field offset ((head delayed) tail ...))
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(free-identifier=? #'field #'head)
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#'(values offset force))
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((_ record field offset ((head thunked) tail ...))
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(free-identifier=? #'field #'head)
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#'(values offset (cut <> record)))
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((_ record field offset (_ tail ...))
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#'(lookup-field+wrapper record field
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(+ 1 offset) (tail ...))))))
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(define-syntax match-record-inner
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(lambda (s)
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(syntax-case s ()
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((_ record type ((field variable) rest ...) body ...)
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#'(let-syntax ((field-offset (syntax-rules ()
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#'(let-syntax ((field-offset+wrapper
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(syntax-rules ()
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((_ f)
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(lookup-field field 0 f)))))
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(let* ((offset (type (map-fields type match-record) field-offset))
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(variable (struct-ref record offset)))
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(lookup-field+wrapper record field 0 f)))))
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(let* ((offset wrap (type (map-fields type match-record)
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field-offset+wrapper))
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(variable (wrap (struct-ref record offset))))
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(match-record-inner record type (rest ...) body ...))))
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((_ record type (field rest ...) body ...)
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;; Redirect to the canonical form above.
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@ -613,10 +634,7 @@ found."
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(syntax-rules ()
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"Bind each FIELD of a RECORD of the given TYPE to it's FIELD name.
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The order in which fields appear does not matter. A syntax error is raised if
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an unknown field is queried.
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The current implementation does not support thunked and delayed fields."
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;; TODO support thunked and delayed fields
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an unknown field is queried."
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((_ record type (fields ...) body ...)
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(if (eq? (struct-vtable record) type)
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(match-record-inner record type (fields ...) body ...)
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@ -561,4 +561,33 @@ Description: 1st line,
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(make-fresh-user-module)))
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(lambda (key . args) key)))
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(test-equal "match-record, delayed field"
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"foo bar bar foo"
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(begin
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(define-record-type* <with-delayed> with-delayed make-with-delayed
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with-delayed?
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(delayed with-delayed-delayed
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(delayed)))
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(let ((rec (with-delayed
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(delayed "foo bar bar foo"))))
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(match-record rec <with-delayed> (delayed)
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delayed))))
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(test-equal "match-record, thunked field"
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'("foo" "foobar")
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(begin
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(define-record-type* <with-thunked> with-thunked make-with-thunked
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with-thunked?
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(normal with-thunked-normal)
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(thunked with-thunked-thunked
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(thunked)))
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(let ((rec (with-thunked
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(normal "foo")
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(thunked (string-append (with-thunked-normal this-record)
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"bar")))))
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(match-record rec <with-thunked> (normal thunked)
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(list normal thunked)))))
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(test-end)
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