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Procedure Arity Inspection
- Bugs and Limitations
- Version history
From the Draft SRFI 102.
This implementation uses the Chicken procedure-information facility.
SRFI 102 (Draft)
procedure-arity[procedure] (procedure-arity PROCEDURE) => ARITY-OBJECT
Produces an arity-object representing the arity of PROCEDURE. If #f results, no information is available for PROCEDURE.
If this procedure produces an exact-non-negative-integer, K, then PROCEDURE accepts exactly K arguments; applying PROCEDURE to some number of arguments other than K will result in an arity error.
If this procedure produces an arity-at-least-object, A, then PROCEDURE accepts (arity-at-least-value A) or more arguments; applying PROCEDURE to some number of arguments less than (arity-at-least-value A) will result in an arity error.
If this procedure produces a list, then PROCEDURE accepts any of the arities described by the elements of the list; applying PROCEDURE to some number of arguments not described by an element of the list will result in an arity error.
procedure-arity-includes?[procedure] (procedure-arity-includes? PROCEDURE K) => BOOLEAN
Returns #t if the PROCEDURE can accept K arguments and #f otherwise. If this procedure returns #f, applying PROCEDURE to K arguments will result in an arity error.
arity-at-least?[procedure] (arity-at-least? OBJECT) => BOOLEAN
Returns #t if OBJECT is an arity-at-least-object and #f otherwise.
arity-at-least-value[procedure] (arity-at-least-value A) => INTEGER
Returns the exact-non-negative-integer denoting the minimum number of arguments required by the given A.
fixed-arity->arity-at-least[procedure] (fixed-arity->arity-at-least K) => ARITY-AT-LEAST-OBJECT
Returns a scalar arity-at-least-object for the supplied exact-non-negative-integer K.
procedure-arity-available?[procedure] (procedure-arity-available? PROCEDURE) => BOOLEAN
Returns #t if the PROCEDURE has arity information.
procedure-fixed-arity?[procedure] (procedure-fixed-arity? PROCEDURE) => BOOLEAN
Returns #t if the PROCEDURE accepts only a fixed number of arguments.
procedure-minimum-arity[procedure] (procedure-minimum-arity PROCEDURE) => INTEGER
Returns the minimum number of arguments acceptable by the PROCEDURE.
procedure-arity-set![procedure] (procedure-arity-set! PROCEDURE [A | K] ...)
PROCEDURE has arity information from one or more A or K.
- scalar arity-at-least-object
append-procedure-arity![procedure] (append-procedure-arity! PROCEDURE A | K)
PROCEDURE has arity information from an A or K.
- scalar arity-at-least-object
- See the "run.scm" test source.
- To call this a work in progress is an understatement. The pulling of procedure arity & name from the lambda-info type is a hack.
- The module procedure-introspection provides the routines for this extension.
- The draft SRFI 102 routines are built from the primitives suggested by Arthur A. Gleckler.
- The author is not a fan of this SRFI (draft!) but it is an interesting exercise.
- Introspection is a poorly explored area of Scheme programming. At least 'R6RS made the distinction between procedure and closure; distinguishing named & anonymous lambda. The author however does not support the enforced static nature of procedure identifier bindings in 'R6RS.
Bugs and Limitations
- When no lambda-info is available the result is undefined.
- When a source is compiled with '-no-lambda-info' no arity info is available.
- Composed & Curried procedures must have an explicitly set arity.
- Support for case-lambda and match-lambda is not automatic.
From the Draft SRFI 102 Document Copyright (C) David Van Horn 2009. All Rights Reserved.
Copyright (C) 2009 Kon Lovett. All rights reserved.
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