Merge pull request #102 from sergiokas/master

Adding small function pointers example in C

1 files changed, 30 insertions, 0 deletions

diff --git a/c.html.markdown b/c.html.markdown
index 8786aa85..132f75dc 100644
--- a/c.html.markdown
+++ b/c.html.markdown
@@ -363,6 +363,36 @@ int area(rect r){
     return r.width * r.height;
 }
 
+///////////////////////////////////////
+// Function pointers 
+///////////////////////////////////////
+/*
+At runtime, functions are located at known memory addresses. Function pointers are
+much likely any other pointer (they just store a memory address), but can be used 
+to invoke functions directly, and to pass handlers (or callback functions) around.
+However, definition syntax may be initially confusing.
+
+Example: use str_reverse from a pointer
+*/
+void str_reverse_through_pointer(char * str_in) {
+    // Define a function pointer variable, named f. 
+    void (*f)(char *); // Signature should exactly match the target function.
+    f = &str_reverse; // Assign the address for the actual function (determined at runtime)
+    (*f)(str_in); // Just calling the function through the pointer
+    // f(str_in); // That's an alternative but equally valid syntax for calling it.
+}
+
+/*
+As long as function signatures match, you can assign any function to the same pointer.
+Function pointers are usually typedef'd for simplicity and readability, as follows:
+*/
+
+typedef void (*my_fnp_type)(char *);
+
+// The used when declaring the actual pointer variable:
+// ...
+// my_fnp_type f; 
+
 ```
 
 ## Further Reading