add methods in c post

2 files changed, 88 insertions, 1 deletions

diff --git a/content/gemtext/gemfeed/2016-11-20-methods-in-c.gmi b/content/gemtext/gemfeed/2016-11-20-methods-in-c.gmi
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+> Written by Paul Buetow 2016-11-20
+
+=> ../ Go back to the main site
+
+# Methods in C
+
+You can do some sort of object oriented programming in the C Programming Language. However, that is very limited. But also very easy and straight forward to use.
+
+## Example
+
+Lets take a look at the following sample program. Basically 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>
+
+typedef struct {
+    double (*calculate)(const double, const double);
+    char *name;
+} something_s;
+
+double multiplication(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"
+    };
+
+    something_s div = (something_s) {
+        .calculate = division,
+        .name = "Division"
+    };
+
+    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));
+}
+```
+
+As you can see you can call the function (pointed by the function pointer) the same way as in C++ or Java via:
+
+```
+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));
+```
+
+Output:
+
+```
+pbuetow ~/git/blog/source [38268]% gcc methods-in-c.c -o methods-in-c
+pbuetow ~/git/blog/source [38269]% ./methods-in-c
+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!
+
+## Taking it further
+
+If you want to get a bit further type "Object-Oriented Programming with ANSI-C" into your favourite internet search engine, you will find some crazy stuff. Some go as far as writing a C preprocessor in AWK, which takes some object oriented pseudo-C and transforms it to plain C so that the C compiler can compile it to machine code. This is actually similar to how the C++ language had its origins.
+
+E-Mail me your throughts at comments@mx.buetow.org!
diff --git a/content/gemtext/gemfeed/atom.xml b/content/gemtext/gemfeed/atom.xml
index 8d28fd1d..1403a85e 100644
--- a/content/gemtext/gemfeed/atom.xml
+++ b/content/gemtext/gemfeed/atom.xml
@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <feed xmlns="http://www.w3.org/2005/Atom">
-    <updated>2021-05-01T13:24:15+01:00</updated>
+    <updated>2021-05-01T18:36:51+01:00</updated>
     <title>buetow.org feed</title>
     <subtitle>Having fun with computers!</subtitle>
     <link href="gemini://buetow.org/gemfeed/atom.xml" rel="self" />
@@ -29,6 +29,17 @@
         </author>
     </entry>
     <entry>
+        <title>Methods in C</title>
+        <link href="gemini://buetow.org/gemfeed/2016-11-20-methods-in-c.gmi" />
+        <id>gemini://buetow.org/gemfeed/2016-11-20-methods-in-c.gmi</id>
+        <updated>2021-05-01T18:36:51+01:00</updated>
+        <summary>You can do some sort of object oriented programming in the C Programming Language. However, that is very limited. But also very easy and straight forward to use.. .....to read on please visit my site.</summary>
+        <author>
+            <name>Paul Buetow</name>
+            <email>comments@mx.buetow.org</email>
+        </author>
+    </entry>
+    <entry>
         <title>Offsite backup with ZFS (Part 2)</title>
         <link href="gemini://buetow.org/gemfeed/2016-04-16-offsite-backup-with-zfs-part2.gmi" />
         <id>gemini://buetow.org/gemfeed/2016-04-16-offsite-backup-with-zfs-part2.gmi</id>