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syntax/parse: fixed error in ~bounds form

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svn: r15728
This commit is contained in:
Ryan Culpepper 2009-08-13 18:28:33 +00:00
parent f37c71c6ee
commit 38e256e6eb
2 changed files with 66 additions and 13 deletions
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3
collects/syntax/private/stxparse/rep.ss
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@ -624,7 +624,8 @@
(list '#:name #'#f)))])
(make ehpat (map increase-depth (pattern-attrs head))
head
(make rep:bounds #'min #'max #'name #'too-few #'too-many))))]))
(make rep:bounds #'min #'max #'name
#'too-few-msg #'too-many-msg))))]))
;; -----

76
collects/syntax/scribblings/parse.scrbl
View File

@ -557,6 +557,7 @@ conditions. The grammar for pattern directives follows:
(code:line #:declare pattern-id syntax-class-id)
(code:line #:declare pattern-id (syntax-class-id expr ...))
(code:line #:with syntax-pattern expr)
(code:line #:attr attr-id expr)
(code:line #:fail-when condition-expr message-expr)
(code:line #:fail-unless condition-expr message-expr)]
@ -598,6 +599,16 @@ given message); otherwise, it continues.
}
@specsubform[(code:line #:attr attr-id expr)]{
Evaluates the @scheme[expr] in the context of all previous attribute
bindings and binds the result to the attribute @scheme[attr-id]. The
result need not be a syntax object; attributes can be bound to any
kind of value.
}
@deftogether[[
@defidform[~or]
@defidform[~and]
@ -605,7 +616,6 @@ given message); otherwise, it continues.
@defidform[~once]
@defidform[~optional]
@defidform[~rest]
@;{@defidform[~struct]}
@defidform[~describe]
@defidform[~!]
@defidform[~bind]
@ -615,6 +625,47 @@ Syntax pattern keywords, recognized by @scheme[syntax-parse].
}
@;{----------}
@section{Pattern Variables and Attributes}
@;{
An @deftech{attribute} is either a @tech{pattern variable}, a
@tech{nested attribute}, or a @tech{computed attribute}.
A pattern consisting of an identifier not in the literals list is a
@deftech{pattern variable}. Pattern variables cannot be used as
ordinary variables; instead, they are used within @scheme[syntax],
@scheme[quasisyntax], etc as part of a syntax template.
Pattern variables have an @deftech{ellipsis depth} based on the number
of ellipses the pattern variable occurs in front of in the
pattern. For example, in the @tech{S-pattern} @scheme[(a (b c ...) ... d)],
the pattern variable @scheme[a] has depth 0, @scheme[b] has
depth 1, @scheme[c] has depth 2, and @scheme[d] has depth 0. The
ellipsis depth of a pattern variable in a pattern determines what
ellipsis depths it may be used at in a template.
Pattern variables annotated with syntax classes also bind
@deftech{nested attributes}, one for each attribute exported by the
syntax class. The names of the nested attributes are computed by
combining the pattern variable name with the syntax class attributes'
names. The ellipsis depth of a nested attribute is the sum of the
pattern variable's depth and the depth of the attribute in the syntax
class. @deftech{Computed attributes} are bound by @scheme[#:attr]
clauses and @scheme[~bind] patterns.
An attribute's ellipsis nesting depth is @emph{not} a guarantee that
its value has that level of list nesting. In particular, @scheme[~or]
and @scheme[~optional] patterns may result in attributes with fewer
than expected levels of list nesting.
@(myexamples
(syntax-parse #'(a b c)
[(~or (x:nat ...) _)
(attribute x)]))
}
@defform[(attribute attr-id)]{
Returns the value associated with the attribute named
@ -625,9 +676,9 @@ nesting.
The values returned by @scheme[attribute] never undergo additional
wrapping as syntax objects, unlike values produced by some uses of
@scheme[syntax], @scheme[quasisyntax], etc. Consequently, the
@scheme[attribute] form is preferred when the attribute value is used
as data, not placed in a syntax object.
@scheme[syntax], @scheme[quasisyntax], etc. Therefore, use
@scheme[attribute] when the attribute value is used as data, not
placed in a syntax object.
}
@ -637,7 +688,7 @@ as data, not placed in a syntax object.
Syntax classes provide an abstraction mechanism for the specification
of syntax. Built-in syntax classes are supplied that recognize basic
classes such as @scheme[identifier]s and @scheme[keyword]s.
classes such as @scheme[identifier] and @scheme[keyword].
Programmers can compose basic syntax classes to build specifications
of more complex syntax, such as lists of distinct identifiers and
formal arguments with keywords. Macros that manipulate the same
@ -754,10 +805,9 @@ Keyword recognized by @scheme[define-syntax-class]. It may not be
used as an expression.
}
@subsection{Attributes}
A syntax class has a set of @deftech{attribute}s. Each attribute has a
A syntax class has a set of @tech{attributes}. Each attribute has a
name, an ellipsis depth, and a set of nested attributes. When an
instance of the syntax class is parsed and bound to a pattern
variable, additional pattern variables are bound for each of the
@ -806,7 +856,7 @@ places. The most common example is the literals for fully expanded
programs, which are used in many analysis and transformation
tools. Specifying literals individually is burdensome and error-prone.
As a remedy, @schememodname[syntax/parse] offers @deftech{literal
set}s. A literal set is defined via @scheme[define-literal-set] and
sets}. A literal set is defined via @scheme[define-literal-set] and
used via the @scheme[#:literal-set] option of @scheme[syntax-parse].
@defform/subs[(define-literal-set name-id (literal ...))
@ -854,7 +904,8 @@ class.
[#rx"^n" nat])
(syntax-parse #'(a b c 1 2 3)
#:conventions (xn-prefixes)
[(x0 x ... n0 n ...) (syntax->datum #'(x0 (x ...) n0 (n ...)))])
[(x0 x ... n0 n ...)
(syntax->datum #'(x0 (x ...) n0 (n ...)))])
]
}
@ -927,13 +978,14 @@ identifier based on their symbolic names rather than their bindings.
@defidform[kernel-literals]{
Literal set containing the identifiers for fully-expanded code. The
set contains all of the forms listed by
Literal set containing the identifiers for fully-expanded code
(@secref[#:doc '(lib "scribblings/reference/reference.scrbl")
"fully-expanded"]). The set contains all of the forms listed by
@scheme[kernel-form-identifier-list], plus @scheme[module],
@scheme[#%plain-module-begin], @scheme[#%require], and
@scheme[#%provide].
@;{See @secref[#:doc '(lib "scribblings/reference/reference.scrbl") 'fully-expanded].}
@;{See @secref[#:doc '(lib "scribblings/reference/reference.scrbl") "fully-expanded"].}
Note that the literal-set uses the names @scheme[#%plain-lambda] and
@scheme[#%plain-app], not @scheme[lambda] and @scheme[#%app].