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box
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Documentation
Implements the "box" data type. A box is a cell containing a single, mutable or immutable, field. The boxed value maybe any Scheme type, including a variable or a location.
Two APIs are provided, the original Chicken box API and a MzScheme/Gambit compatible API.
Box syntax
The lexical syntax of a box containing the object OBJECT is `#&OBJECT'.
Only mutable boxes can be recovered. An immutable, variable, or location box will lose identity when printed.
make-box
- (make-box [INITIAL [IMMUTABLE? #f]]) -> boxprocedure
Returns a BOX with, optional, initial value INITIAL.
The BOX is mutable unless the IMMUTABLE? argument is #t.
An attempt to mutate an immutable box will signal an exception.
make-box-variable
- (make-box-variable VARIABLE [IMMUTABLE? #f]) -> boxsyntax
Returns a boxed reference to the VARIABLE, which must be in lexical-scope.
The BOX is mutable unless the IMMUTABLE? argument is #t.
An attempt to mutate an immutable box will signal an exception.
make-box-location
- (make-box-location TYPE INITIAL-VALUE [IMMUTABLE? #f]) -> boxsyntax
Returns a boxed reference to a location of TYPE and INITIAL-VALUE.
The BOX is mutable unless the IMMUTABLE? argument is #t.
An attempt to mutate an immutable box will signal an exception.
Unavailable in EVALuated source.
box?
- box? OBJECTprocedure
Is OBJECT a BOX?
box-mutable?
- box-mutable? OBJECTprocedure
Is OBJECT a mutable BOX?
box-immutable?
- box-immutable? OBJECTprocedure
Is OBJECT an immutable BOX?
box-variable?
- box-variable? OBJECTprocedure
Is OBJECT a boxed variable?
box-location?
- box-location? OBJECTprocedure
Is OBJECT a boxed location?
box-set!
- box-set! BOX OBJECTprocedure
Changes the boxed value of BOX to OBJECT. Will signal an exception for an immutable {{BOX}.
box-ref
- box-ref BOXprocedure
Returns the boxed value of BOX.
box-location
- (box-location BOX [WEAK? #f]) -> locationprocedure
Returns a LOCATION object for a boxed variable, location or locatable box. Signals an exception otherwise.
The locative is "strong" unless the WEAK? argument is #t. The WEAK? argument is ignored for boxed variables and locations.
The location of a boxed value or boxed location is the box. The location of a boxed variable is the same as (location (box-ref BOX)); currently the location of a symbol may not be taken.
See Locations.
box-swap!
- box-swap! BOX FUNC #!optional OBJECT...procedure
Changes the boxed value of BOX to (FUNC <BOX-VALUE> OBJECT...). Will signal an exception for an immutable BOX}. Returns the new value of {{BOX.
make-box-variable-closure
- make-box-variable-closure IMMUTABLE? REF SETprocedure
- IMMUTABLE?
- boolean
- REF
- (-> *)
- SET
- (* -> void)
make-box-location-closure
- make-box-location-closure IMMUTABLE? REF SET REFLOCprocedure
- IMMUTABLE?
- boolean
- REF
- (-> *)
- SET
- (* -> void)
- REFLOC
- (-> location)
box
- box OBJECTprocedure
Returns a mutable BOX with initial value OBJECT.
set-box!
- set-box! BOX OBJECTprocedure
Changes the boxed value of BOX to OBJECT. Will signal an exception for an immutable {{BOX}.
unbox
- unbox BOXprocedure
Returns the boxed value of BOX.
Usage
(require-extension box)
or
(require-library box) ... (import box)
Examples
#;1> (define b (box 0)) #;2> b #&0 #;3> (define (inc-box! bx) (set! (box-ref bx) (add1 (unbox bx)))) #;4> (inc-box! b) #;5> (unbox b) 1 #;6> (box-swap! b add1) 2 #;7> (box-swap! b * 3) 6 #;8> (box-ref b) 6
Notes
Requirements
Bugs and Limitations
The location of a boxed variable is rather useless.
Author
Version history
- 2.4.0
- Add make-box-variable-closure & make-box-location-closure.
- 2.3.3
- Updated type information.
- 2.3.2
- Added type information.
- 2.3.1
- 2.3.0
- Added box-swap!. Fix for print of mutable box.
- 2.2.4
- Bug fix for Chicken 4.6.3
- 2.2.3
- 2.2.2
- 2.2.1
- 2.1.0
- Bug fix for box?. Added direct calls (only for use when the actual type is known.)
- 2.0.0
- Port to hygienic Chicken. Reduced memory footprint for basic usage. Dropped keyword arguments.
License
Copyright (C) 2009-2018 Kon Lovett. All rights reserved.
Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the Software), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED ASIS, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.