<div dir="ltr">You can simulate and ->im with ->i by adding a mandatory (first) argument with contract any/c.<div> </div><div>Robby</div></div><div class="gmail_extra"> <div class="gmail_quote">On Sat, Aug 31, 2013 at 6:39 AM, Diego Sevilla Ruiz <<a href="mailto:dsevilla@ditec.um.es" target="_blank">dsevilla@ditec.um.es</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Hi all: I have encountered a situation in which I don't know how to specify the contract for a method that: 1. Has a final optional argument 2. The value of the optional argument makes the method change the return type of the method. It is similar to this: (define/public (get-whatever (pos #f)) (if (not pos) inner-vector-of-int (vector-ref inner-vector-of-int pos))) (that is, if you don't specify a position, return the whole vector, but if you specify a position, return that position). For what I've seen in the documentation, there exists the ->i function that allos the specification of named parameters, such as (not working but you get the idea): (->i () ;; mandatory ([pos (or/c number? boolean?)]) ;; optional [result (pos) (or/c (and/c (=/c #f pos) (vectorof number?)) (and/c (number? pos) number?))]) (I don't think the result expression is correct, but it expresses what I want). The real problem comes with methods, because I have ->m and ->dm, but not ->im (->dm does not allow specifying dependent previous values in the result, for example, as far as I know). So the question is, how to write a method contract for this method? Thanks in advance, diego. -- Diego Sevilla Ruiz -- <a href="http://ditec.um.es/~dsevilla/" target="_blank">http://ditec.um.es/~dsevilla/</a> -- <a href="mailto:dsevilla@um.es" target="_blank">dsevilla@um.es</a> _.___ Dep. Ingeniería y Tecnología de Computadores, Facultad de Informática D|TEC Univ.de Murcia,Campus Espinardo,30080 Murcia (SPAIN),Tel.<a href="tel:%2B34868887571" value="+34868887571" target="_blank">+34868887571</a> ____________________ Racket Users list: <a href="http://lists.racket-lang.org/users" target="_blank">http://lists.racket-lang.org/users</a> </blockquote></div> </div>