7.2

### 4arity+keywords

#### 4.1Procedure arities with keywords

 (require kw-utils/arity+keywords) package: kw-utils

struct

 (struct arity+keywords (arity required-kws allowed-kws)
#:transparent)
arity : procedure-arity?
required-kws : (listof keyword?)
allowed-kws : (or/c (listof keyword?) #f)
represents a procedure’s arity including the keywords required and keywords allowed.

The arity field represents the arity produced by procedure-arity.

The next 2 fields (required-kws and allowed-kws) represent the 2 values produced by procedure-keywords.

A #f value for allowed-kws means that it accepts all keywords.

The guard procedure also sorts the keyword lists for you.

 procedure proc : procedure?
returns an arity+keywords instance representing the arity and keyword-arity of proc.

It is defined like this:
 (define (procedure-arity+keywords proc) (define arity (procedure-arity proc)) (define-values (req-kws allowed-kws) (procedure-keywords proc)) (arity+keywords arity req-kws allowed-kws))

Examples:
> (require kw-utils/arity+keywords)
> (define proc (make-keyword-procedure void))
> (procedure-arity+keywords proc)

(arity+keywords (arity-at-least 0) '() #f)

> (procedure-arity+keywords (procedure-reduce-arity proc 5))

(arity+keywords 5 '() '())

 > (procedure-arity+keywords (procedure-reduce-keyword-arity/sort proc 3 '(#:kw #:other-kw) '(#:kw #:other-kw #:optional-kw)))

(arity+keywords 3 '(#:kw #:other-kw) '(#:kw #:optional-kw #:other-kw))

procedure

 (procedure-reduce-arity+keywords proc arity+kws) → procedure?
proc : procedure?
arity+kws : arity+keywords?
like procedure-reduce-arity, except that it accepts an arity+keywords and handles the keyword-arity as well.

It is defined like this:
 (define (procedure-reduce-arity+keywords proc a) (procedure-reduce-keyword-arity proc (arity+keywords-arity a) (arity+keywords-required-kws a) (arity+keywords-allowed-kws a)))

Examples:
> (require kw-utils/arity+keywords)
> (define proc (make-keyword-procedure void))
> (procedure-arity proc)

(arity-at-least 0)

> (procedure-keywords proc)
 '() #f
 > (define proc-with-arity (procedure-reduce-arity+keywords proc (arity+keywords 5 '(#:kw #:other-kw) '(#:kw #:other-kw #:optional-kw))))
> (procedure-arity proc-with-arity)

5

> (procedure-keywords proc-with-arity)
 '(#:kw #:other-kw) '(#:kw #:optional-kw #:other-kw)

procedure

 (procedure-reduce-keyword-arity/sort proc arity required-kws allowed-kws) → procedure?
proc : procedure?
arity : procedure-arity?
required-kws : (listof keyword?)
allowed-kws : (or/c (listof keyword?) #f)
like procedure-reduce-keyword-arity, but without the constraint that the keywords in required-kws or allowed-kws must be sorted.

It is equivalent to (procedure-reduce-arity+keywords proc (arity+keywords arity required-kws allowed-kws)).

 procedure(arity+keywords-matches? arity+kws n kws) → boolean? arity+kws : arity+keywords? n : natural-number/c kws : (listof keyword?)
determines whether the given arity+kws accepts the n by-position arguments and the keywords in kws.

procedure

 (procedure-arity+keywords-matches? proc n kws) → boolean?
proc : procedure?
n : natural-number/c
kws : (listof keyword?)

 procedure n : natural-number/c kws : (listof keyword?)
produces a flat contract (also a predicate) that accepts procedures that accept n by-position arguments and accepts the keywords in kws.

 procedure(arity+keywords-includes? a1 a2) → boolean? a1 : arity+keywords? a2 : arity+keywords?
like arity-includes?, but for arity+keywords instances. But most of the time when when you would use arity-includes?, you really want arity+keywords-matches?.

 procedure(arity+keywords-combine/or arity+kws ...) → arity+keywords? arity+kws : arity+keywords?
combines the arity+kwses into one arity+keywords instance in an or-like way.

Examples:
> (require kw-utils/arity+keywords)
 > (arity+keywords-combine/or (arity+keywords 1 '(#:a)     '(#:a #:b #:c)) (arity+keywords 2 '(#:a #:b) '(#:a #:b #:d)))

(arity+keywords '(1 2) '(#:a) '(#:a #:b #:c #:d))

 procedure(arity+keywords-combine/and arity+kws ...) → arity+keywords? arity+kws : arity+keywords?
combines the arity+kwses into one arity+keywords instance in an and-like way.

Examples:
> (require kw-utils/arity+keywords)
 > (arity+keywords-combine/and (arity+keywords '(1 2) '(#:a) '(#:a #:b #:c #:d)) (arity+keywords '(2 3) '(#:b) '(#:a #:b #:c #:e)))

(arity+keywords 2 '(#:a #:b) '(#:a #:b #:c))

#### 4.2Getting the arity from function arguments syntax

 (require kw-utils/arity+keywords/syntax) package: kw-utils

 procedure(kw-formals->arity+keywords fmls-stx) → arity+keywords? fmls-stx : syntax?
Given the args in (lambda args body), returns an arity+keywords value representing the arity and keywords of the function.

Examples:
 > (require kw-utils/arity+keywords/syntax) > (kw-formals->arity+keywords #'()) (arity+keywords 0 '() '()) > (kw-formals->arity+keywords #'(a b c)) (arity+keywords 3 '() '()) > (kw-formals->arity+keywords #'(a b [c 2])) (arity+keywords '(2 3) '() '()) > (kw-formals->arity+keywords #'(a b . rst)) (arity+keywords (arity-at-least 2) '() '()) > (kw-formals->arity+keywords #'(a #:b b)) (arity+keywords 1 '(#:b) '(#:b)) > (kw-formals->arity+keywords #'(a #:b [b 1])) (arity+keywords 1 '() '(#:b)) > (kw-formals->arity+keywords #'(#:a a . rst)) (arity+keywords (arity-at-least 0) '(#:a) '(#:a))

 procedure(kw-formals->arity fmls-stx) → normalized-arity? fmls-stx : syntax?
 procedure(kw-formals->required-kws fmls-stx) → (listof keyword?) fmls-stx : syntax?
 procedure(kw-formals->allowed-kws fmls-stx) → (listof keyword?) fmls-stx : syntax?
Like kw-formals->arity+keywords, but just for the positional-argument arity, required keywords, and allowed keywords.