From eb56eec92251716d9bfa21b8c1d73b042dd8aab7 Mon Sep 17 00:00:00 2001 From: Paul Buetow Date: Sun, 9 Apr 2023 13:52:04 +0300 Subject: Update content for html --- ...20-object-oriented-programming-with-ansi-c.html | 91 +++++++++++++--------- 1 file changed, 53 insertions(+), 38 deletions(-) (limited to 'gemfeed/2016-11-20-object-oriented-programming-with-ansi-c.html') diff --git a/gemfeed/2016-11-20-object-oriented-programming-with-ansi-c.html b/gemfeed/2016-11-20-object-oriented-programming-with-ansi-c.html index 85ececb0..a8eeaea7 100644 --- a/gemfeed/2016-11-20-object-oriented-programming-with-ansi-c.html +++ b/gemfeed/2016-11-20-object-oriented-programming-with-ansi-c.html @@ -27,61 +27,73 @@
Let's have a look at the following sample program. All you have to do is to add a function pointer such as "calculate" to the definition of struct "something_s". Later, during the struct initialization, assign a function address to that function pointer:

-
-#include <stdio.h>
+
+
#include <stdio.h>
 
-typedef struct {
-    double (*calculate)(const double, const double);
-    char *name;
-} something_s;
+typedef struct {
+    double (*calculate)(const double, const double);
+    char *name;
+} something_s;
 
-double multiplication(const double a, const double b) {
-    return a * b;
-}
+double multiplication(const double a, const double b) {
+    return a * b;
+}
 
-double division(const double a, const double b) {
-    return a / b;
-}
+double division(const double a, const double b) {
+    return a / b;
+}
 
-int main(void) {
-    something_s mult = (something_s) {
-        .calculate = multiplication,
-        .name = "Multiplication"
-    };
+int main(void) {
+    something_s mult = (something_s) {
+        .calculate = multiplication,
+        .name = "Multiplication"
+    };
 
-    something_s div = (something_s) {
-        .calculate = division,
-        .name = "Division"
-    };
+    something_s div = (something_s) {
+        .calculate = division,
+        .name = "Division"
+    };
 
-    const double a = 3, b = 2;
+    const double a = 3, b = 2;
 
-    printf("%s(%f, %f) => %f\n", mult.name, a, b, mult.calculate(a,b));
-    printf("%s(%f, %f) => %f\n", div.name, a, b, div.calculate(a,b));
-}
+    printf("%s(%f, %f) => %f\n", mult.name, a, b, mult.calculate(a,b));
+    printf("%s(%f, %f) => %f\n", div.name, a, b, div.calculate(a,b));
+}
 

 

 As you can see, you can call the function (pointed by the function pointer) with the same syntax as in C++ or Java:

 

-
-printf("%s(%f, %f) => %f\n", mult.name, a, b, mult.calculate(a,b));
-printf("%s(%f, %f) => %f\n", div.name, a, b, div.calculate(a,b));
+
+
printf("%s(%f, %f) => %f\n", mult.name, a, b, mult.calculate(a,b));
+printf("%s(%f, %f) => %f\n", div.name, a, b, div.calculate(a,b));
 

 

 However, that's just syntactic sugar for:

 

-
-printf("%s(%f, %f) => %f\n", mult.name, a, b, (*mult.calculate)(a,b));
-printf("%s(%f, %f) => %f\n", div.name, a, b, (*div.calculate)(a,b));
+
+
printf("%s(%f, %f) => %f\n", mult.name, a, b, (*mult.calculate)(a,b));
+printf("%s(%f, %f) => %f\n", div.name, a, b, (*div.calculate)(a,b));
 

 

 Output:

 

-
-pbuetow ~/git/blog/source [38268]% gcc oop-c-example.c -o oop-c-example
-pbuetow ~/git/blog/source [38269]% ./oop-c-example
-Multiplication(3.000000, 2.000000) => 6.000000
-Division(3.000000, 2.000000) => 1.500000
+
+
pbuetow ~/git/blog/source [38268]% gcc oop-c-example.c -o oop-c-example
+pbuetow ~/git/blog/source [38269]% ./oop-c-example
+Multiplication(3.000000, 2.000000) => 6.000000
+Division(3.000000, 2.000000) => 1.500000
 

 

 Not complicated at all, but nice to know and helps to make the code easier to read!

@@ -90,8 +102,11 @@ Division(3.000000, 2.000000) => 1.500000
 

 However, that's not really how it works in object-oriented languages such as Java and C++. The method call in this example is not a method call as "mult" and "div" in this example are not "message receivers". I mean that the functions can not access the state of the "mult" and "div" struct objects. In C, you would need to do something like this instead if you wanted to access the state of "mult" from within the calculate function, you would have to pass it as an argument:

 

-
-mult.calculate(mult,a,b));
+
+
mult.calculate(mult,a,b));
 

 

 
Real object oriented programming with C


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