Exercise 12

Informatik_I/Exercise_12/Task_2b/README.org

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+#+title: Task 2b: Understanding Pointers - First_Char
+#+author: JirR02
+
+* Task Description
+
+  Complete the definition of function =first_char= by editing the file =first_char.cpp= according to its specified pre- and post conditions.
+
+  We provide a test program using the implemented function to find the index of the first character in a string.
+
+** Input
+
+   The program accepts
+
+   * a string s (it may contain whitespaces), followed by a newline, and
+   * a character c for which to search for the index first occurence
+
+   For example
+
+   #+BEGIN_src shell
+   jabberwock 
+   b
+   #+END_src
+
+** Output
+
+   The pointer to the first element at string =s= where it is equal to character =c=.
+
+   If there is no match, returns a null pointer.
+
+* Solution
+
+  #+BEGIN_src cpp
+  #include "first_char.h"
+
+  // PRE: str points within an allocated memory block which contains
+  //      the null character (numerical ASCII value 0) at its last location,
+  //      and nowhere else.
+  // POST: Returns the pointer to first element at str or after
+  //       that is equal to ch, otherwise return nullptr.
+  const char *first_char(const char *str, const char ch) {
+    for (;; str++)
+      if (*str == ch)
+        return str;
+      else if (*str == '\0')
+        return nullptr;
+  }
+  #+END_src
+
+  --------------
+
+  Made by JirR02 in Switzerland 🇨🇭