Rename isValid to is_valid (#552)

This is to follow the OCaml naming conventions.

Author: TheRealOwenRees

exercises/practice/isbn-verifier/.meta/example.ml

@@ -1,4 +1,4 @@
-let isValid s =
+let is_valid s =
   let chars = List.init (String.length s) (String.get s) in
 
   let is_digit c = c >= '0' && c <= '9' in

exercises/practice/isbn-verifier/isbn_verifier.ml

@@ -1,2 +1,2 @@
-let isValid _ =
+let is_valid _ =
   failwith = "'isValid' is missing"

exercises/practice/isbn-verifier/isbn_verifier.mli

@@ -1 +1 @@
-val isValid : string -> bool
+val is_valid : string -> bool

exercises/practice/isbn-verifier/test.ml

@@ -5,43 +5,43 @@ let ae exp got _test_ctxt = assert_equal ~printer:string_of_bool exp got
 
 let tests = [
   "valid isbn" >::
-  ae true (isValid "3-598-21508-8");
+  ae true (is_valid "3-598-21508-8");
   "invalid isbn check digit" >::
-  ae false (isValid "3-598-21508-9");
+  ae false (is_valid "3-598-21508-9");
   "valid isbn with a check digit of 10" >::
-  ae true (isValid "3-598-21507-X");
+  ae true (is_valid "3-598-21507-X");
   "check digit is a character other than X" >::
-  ae false (isValid "3-598-21507-A");
+  ae false (is_valid "3-598-21507-A");
   "invalid check digit in isbn is not treated as zero" >::
-  ae false (isValid "4-598-21507-B");
+  ae false (is_valid "4-598-21507-B");
   "invalid character in isbn is not treated as zero" >::
-  ae false (isValid "3-598-P1581-X");
+  ae false (is_valid "3-598-P1581-X");
   "X is only valid as a check digit" >::
-  ae false (isValid "3-598-2X507-9");
+  ae false (is_valid "3-598-2X507-9");
   "valid isbn without separating dashes" >::
-  ae true (isValid "3598215088");
+  ae true (is_valid "3598215088");
   "isbn without separating dashes and X as check digit" >::
-  ae true (isValid "359821507X");
+  ae true (is_valid "359821507X");
   "isbn without check digit and dashes" >::
-  ae false (isValid "359821507");
+  ae false (is_valid "359821507");
   "too long isbn and no dashes" >::
-  ae false (isValid "3598215078X");
+  ae false (is_valid "3598215078X");
   "too short isbn" >::
-  ae false (isValid "00");
+  ae false (is_valid "00");
   "isbn without check digit" >::
-  ae false (isValid "3-598-21507");
+  ae false (is_valid "3-598-21507");
   "check digit of X should not be used for 0" >::
-  ae false (isValid "3-598-21515-X");
+  ae false (is_valid "3-598-21515-X");
   "empty isbn" >::
-  ae false (isValid "");
+  ae false (is_valid "");
   "input is 9 characters" >::
-  ae false (isValid "134456729");
+  ae false (is_valid "134456729");
   "invalid characters are not ignored after checking length" >::
-  ae false (isValid "3132P34035");
+  ae false (is_valid "3132P34035");
   "invalid characters are not ignored before checking length" >::
-  ae false (isValid "3598P215088");
+  ae false (is_valid "3598P215088");
   "input is too long but contains a valid isbn" >::
-  ae false (isValid "98245726788");
+  ae false (is_valid "98245726788");
 ]
 
 let () =

templates/isbn-verifier/test.ml.tpl

@@ -6,7 +6,7 @@ let ae exp got _test_ctxt = assert_equal ~printer:string_of_bool exp got
 let tests = [
   {{#cases}}
     "{{description}}" >::
-      ae {{#input}}{{expected}} (isValid {{isbn}}){{/input}};
+      ae {{#input}}{{expected}} (is_valid {{isbn}}){{/input}};
   {{/cases}}
 ]