D: add countLettersInTextFile.d

.gitignore

@@ -1,6 +1,7 @@
 # ---> C
 # Prerequisites
 *.d
+!d-programming/**.d
 
 # Object files
 *.o
@@ -213,3 +214,35 @@ cython_debug/
 #  and can be added to the global gitignore or merged into this file.  For a more nuclear
 #  option (not recommended) you can uncomment the following to ignore the entire idea folder.
 #.idea/
+
+# ---> D
+# Compiled Object files
+*.o
+*.obj
+
+# Compiled Dynamic libraries
+*.so
+*.dylib
+*.dll
+
+# Compiled Static libraries
+*.a
+*.lib
+
+# Executables
+*.exe
+
+# DUB
+.dub
+docs.json
+__dummy.html
+docs/
+
+# Code coverage
+*.lst
+
+# Swap files of editors
+*.*~
+
+# Build directory
+build/

d-programming/countLettersInTextFile.d

@@ -0,0 +1,16 @@
+import std.algorithm.iteration : filter;
+import std.algorithm.searching : count;
+import std.ascii : isAlpha, isWhite;
+import std.file : read;
+import std.stdio : writefln;
+
+void main()
+{
+	auto fileContent = cast(string)read("file.txt");
+	auto totalLetters =
+		count(filter!(a => isAlpha(a) || isWhite(a))(fileContent));
+	auto percentage = (totalLetters * 100) / cast(double)fileContent.length;
+
+	writefln("Percentage of letters: %.0f", percentage);
+}
+