Camel Case
August 29, 2017
Some programmers write variable names in camelCase, each word starting with a capital letter, while other programmers separate words with underscores like_this.
Your task is to write programs that convert between the two forms. When you are finished, you are welcome to read or run a suggested solution, or to post your own solution or discuss the exercise in the comments below.
Programming Praxis 
This gives a slightly different answer (when the first character is upper case as it doesn’t prefix it with an underscore…;
sub from_cc { return join '_', map { $_ } split /(?=[A-Z])/, shift; } sub to_cc { my $t = join '', map { ucfirst lc $_ } split /_/, shift; substr $t,0,1,lc substr $t,0,1; return $t; }In Python. Probably the regex split can be improved to handle multiple capitals, but I did not manage yet.
def split_on_case(txt): return regex.split("(?V1)(?<=[a-z])(?=[A-Z])", txt) def split_on_case(txt): S, last = [], "" G = ["".join(g) for k, g in groupby(txt, str.isupper)] for g in G: if str.isupper(g): if g == G[-1]: S.append(g) elif len(g) > 1: S.append(g[:-1]) last = g[-1] else: last = g else: S.append("".join((last, g))) return S def camel_underscore(txt): elts = [w.lower() for w in split_on_case(txt)] return "_".join(elts) def underscore_camel(txt): elts = [w[0].upper() + w[1:] for w in txt.split("_")] return "".join(elts) print(camel_underscore("CamelCase")) print(underscore_camel("def_with_underscores")) print(camel_underscore("getHTPPClient")) print(camel_underscore("getHTPP")) print(underscore_camel("get_HTTP_client")) """ with lengthy split method camel_case DefWithUnderscores get_htpp_client get_htpp GetHTTPClient with regex camel_case DefWithUnderscores get_htppclient get_htpp GetHTTPClient """Why would anyone want to convert to the underscore format? Although this may be a very interesting exercise programmatically, I find its use case quite limited.
@Zack: Underscore case is the convention in some languages, including Oracle SQL and PL/SQL which I use every day in my regular job.
On Tue, Aug 29, 2017 at 9:08 AM, Programming Praxis wrote:
>
(import (scheme base) (srfi 1) (scheme char) (scheme write)) ;;; Naive versions, based on literal interpretation (define (camel->snake str) (list->string (reverse (fold (lambda (c lst) (if (char-upper-case? c) (cons (char-downcase c) (cons #\_ lst)) (cons c lst))) '() (string->list str))))) (camel->snake "fooBarBazItIs") (define (snake->camel str) (list->string (reverse (fold (lambda (c lst) (if (and (pair? lst) (char=? #\_ (car lst))) (cons (char-upcase c) (cdr lst)) (cons c lst))) '() (string->list str))))) (snake->camel (camel->snake "fooBarBazItIs")) ;;; A different version of camel->snake. ;; We will use the rule that an uppercase character X is treated as ;; special (i.e., it is subjected to the rewriting X -> _x) iff there ;; is a lowercase character immediately to the left or (inclusive) ;; right of X. (define (camel-hump? str idx) (and (char-upper-case? (string-ref str idx)) (or (and (> idx 0) (char-lower-case? (string-ref str (- idx 1)))) (and (< idx (- (string-length str) 1)) (char-lower-case? (string-ref str (+ idx 1))))))) (define (show-humps str) (map (lambda (i) (cons (string-ref str i) (camel-hump? str i))) (iota (string-length str)))) (define (camel->snake/grouping str) (apply string-append (list-tabulate (string-length str) (lambda (i) (if (camel-hump? str i) (string #\_ (string-ref str i)) (string (string-ref str i))))))) (map camel->snake/grouping '("HTTPClient" "getHTTP" "XMLServer" "XMLHTTPServer")) (map snake->camel (map camel->snake/grouping '("HTTPClient" "getHTTP" "XMLServer" "XMLHTTPServer"))) ;;;A shorter version of the split function.
def split_on_case(txt): program = re.compile("[A-Z]?[a-z]+") splits = set([0, len(txt)]) for m in program.finditer(txt): splits.update(m.span()) return [txt[b:e] for b, e in pairwise(sorted(splits))]Solution for ASCII characters in Ruby.
def camel_to_snake(camel_string) camel_string.gsub(/[a-z][A-Z]/) { |x| x.chars.join('_').downcase } end def snake_to_camel(snake_string) snake_string.gsub(/_[a-z]/) { |x| x.chars.last.upcase } endThe test…
Outputs:
Solution for ASCII characters in Ruby. (Posting again without Emojis)
def camel_to_snake(camel_string) camel_string.gsub(/[a-z][A-Z]/) { |x| x.chars.join('_').downcase } end def snake_to_camel(snake_string) snake_string.gsub(/_[a-z]/) { |x| x.chars.last.upcase } endThe test…
Outputs:
@programmingpraxis fell free to delete my previous post.