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text.edn
- EDN parsing and constructionEDN (Extensible Data Notation) is a subset of Clojure literals for data exchange. This module provides utilities to read and write EDN format. See https://github.com/edn-format/edn for the details of EDN.
EDN | Gauche | Note |
true | #t | |
false | #f | |
nil | nil | Clojure’s nil is not a symbol but a special value; since Clojure
can’t have a symbol named nil, we can map it to Gauche’s symbol nil . |
number | <real> | Integers and floating point numbers.
The N and M suffixes in Clojure are ignored. |
symbol | <symbol> | Clojure’s symbol name has some restrictions, so not all Gauche symbols
map to EDN symbols.
Clojure’s namespace-prefixed symbol, e.g. foo/bar simply maps to
Gauche’s symbol foo/bar ; we provide utility procedure to extract
namespace and basename parts. |
keyword | <keyword> | Clojure has keywords distinct from symbols. They are mapped to Gauche’s
keywords (which is a subtype of symbols).
Gauche’s keywords can also be symbols, but
no Clojure symbols begin with : so there won’t be a conflict. |
list | <list> | Clojure lists are Gauche lists. Note that Clojure doesn’t allow improper lists. |
vector | <vector> | Clojure vectors are Gauche vectors. |
map | <hash-table> | Clojure’s map becomes Gauche’s hashtable with edn-comparator
for hashing and comparison. |
set | <set> | Clojure’s set becomes Gauche’s set with edn-comparator
for comparison. See scheme.set - R7RS sets for interface of sets. |
tagged object | <edn-object> | Tagged objects are mapped to <edn-object> by default.
You can customize the parser/writer to map tagged objects with a
specific tag to a specific Gauche objects. |
When the parser encounters an error, this condition is thrown.
Inherits <error>
.
{text.edn} Read one EDN representation from the given input port, and returns Gauche object created from it. If iport is omitted, current input port is assumed.
When the parser encounters unparsable sequence,
it raises <edn-parse-error>
.
Note that iport may be read ahead for characters. Suppose
the input consists of abc{:a b}
, i.e. a symbol immediately
followed by a map. The parser need to read {
to know the
end of the symbol. The read-ahead brace isn’t pushed back
to the iport. So it would be a problem if you keep reading
more EDN subsequently. Use parse-edn*
if you want to read
multiple objects.
{text.edn} Read EDN representations repeatedly from the given input port and returns a list of them. If iport is omitted, current input port is assumed.
When the parser encounters unparsable sequence,
it raises <edn-parse-error>
.
{text.edn} A convenience procedure to parse EDN representation in a string str, and returns the read object.
When the parser encounters unparsable sequence,
it raises <edn-parse-error>
.
(parse-edn-string "[1 2 (3 4) {:a 5}]") ⇒ #(1 2 (3 4) #<hash-table general 0x1f05780>)
{text.edn} Write out an EDN representation of object obj to the output port oport. If oport is omitted, current output port is assumed.
If obj contains an object that doesn’t have a defined EDN representation, a generic function edn-write is called on it. See Customization heading below. If no method is defined for the object, an error is signaled.
{text.edn} Returns an EDN representation of obj in a string.
If obj contains an object that doesn’t have a defined EDN representation, a generic function edn-write is called on it. See Customization heading below. If no method is defined for the object, an error is signaled.
(construct-edn-string ’#(1 2 "abc")) ⇒ "[1 2 \"abc\"]"
{text.edn} Test equality of two objects that are read from EDN representation.
{text.edn}
A comparator that uses edn-equal?
for the equality predicate.
Corresponding has function is also included.
EDN maps and sets become Gauche hash-tables and sets with this comparator.
{text.edn} Convenience procedures to create hash-tables and sets compatible for EDN.
{text.edn} EDN tagged object becomes an instance of this class by default. The instance has the following slots, both are immutable:
Object’s tag. A symbol.
Object’s payload. Can be any object that can be representable in EDN.
For example, when you read #myobject {:a 1 :b 2}
,
the tag is myobject
and the payload is a hashtable
containing mapping {:a 1 :b 2}
.
{text.edn}
Returns a new <edn-object>
instance.
Note: Arguments are not checked. It’s caller’s responsibility to
pass valid arguments to guarantee it’s serializable as EDN.
{text.edn}
Returns #t
iff obj is an instance of <edn-object>
.
{text.edn} Returns the tag and the payload of edn-object, respectively.
{text.edn} Return prefix and basename part of the symbol, respectively.
(edn-symbol-prefix 'foo/bar) ⇒ foo (edn-symbol-basename 'foo/bar) ⇒ bar (edn-symbol-prefix 'bar) ⇒ #f (edn-symbol-basename 'bar) ⇒ bar
{text.edn}
Returns #t
iff a string str can be a valid Clojure symbol name.
It may have namespace prefix.
You can map EDN tagged objects to other Gauche objects.
{text.edn}
Tag is a symbol, and handler is #f
or a procedure
that takes a tag symbol and a payload object.
Tag must have a name valid as Clojure symbol, or an error is signaled.
After the parser reads a tagged object with a symbol tag
and payload, it calls handler, and the returned object
becomes the result of the parser, instead of <edn-object>
.
Registering #f
removes the previously registered handler.
This procedure is thread-safe.
The following example makes EDN #u8vector[1 2 3 4]
to be read
as #u8(1 2 3 4)
:
(register-edn-object-handler! 'u8vector (^[tag vec] (vector->u8vector vec)))
{text.edn}
Returns a handler registered with a symbol tag. If a handler
is not registered for tag, #f
is returned.
This procedure is thread-safe.
{text.edn}
Write EDN representation of obj to the current output port.
The construct-edn
procedure calls this internally.
To write out a Gauche object as EDN tagged object, define a method to
this generic function. In the method you can call edn-write
recursively to write out components of the object.
The following example writes #u8(1 2 3 4)
as
EDN #u8vector[1 2 3 4]
:
(define-method edn-write ((x <u8vector>)) (display "#u8vector") (edn-write (u8vector->vector x)))
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