We are finding a file (or directory) with name "tarzan" inside all directories inside given path upto given depth. Recursion is needed here, because tarzan-near-top-of-tree? calls tarzan-in-directory? and tarzan-in-directory? calls tarzan-near-top-of-tree? for each file in given directory.
суббота, 8 мая 2021 г. в 12:50:09 UTC+5, Utkarsh Singh: > Hi, > > First of all I would like to thank Racket community for creating and > maintaining top quality documentation at https://docs.racket-lang.org/ > and even providing a local copy for it. > > Currently I am having some difficulties in understanding this letrec > example from Racket Guide docs > ( > https://docs.racket-lang.org/guide/let.html#%28part._.Recursive_.Binding__letrec%29 > ): > > (letrec ([tarzan-near-top-of-tree? > (lambda (name path depth) > (or (equal? name "tarzan") > (and (directory-exists? path) > (tarzan-in-directory? path depth))))] > [tarzan-in-directory? > (lambda (dir depth) > (cond > [(zero? depth) #f] > [else > (ormap > (λ (elem) > (tarzan-near-top-of-tree? (path-element->string elem) > (build-path dir elem) > (- depth 1))) > (directory-list dir))]))]) > (tarzan-near-top-of-tree? "tmp" > (find-system-path 'temp-dir) > 4)) > > Problem: > I having some problem on how recursion is working here and what is the > problem we are solving here. Are we finding a file with (name? > "tarzan") or something else? > > -- > Utkarsh Singh > http://utkarshsingh.xyz > -- You received this message because you are subscribed to the Google Groups "Racket Users" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/a3d31da0-c9b7-4aac-a541-15137197d941n%40googlegroups.com.
