Survey analytics, mixins!

Currently I'm working on my Degree in ICT industry project. For this I am using D.
I'm currently in the requirements phase and doing some requirements gathering. To make sense of all this data I'm writing a tool in D to analyse it.

Unfortunately I had code such as:

	YesNoSometimes assmtfdbkParse(string text) {
	string[] stes = text.split(",");
	foreach(ste; stes) {
	switch(ste) {
	case "Yes definately":
	return YesNoSometimes.Yes;
	case "Depends on the student":
	return YesNoSometimes.Sometimes;
	default:
	return YesNoSometimes.No;
	}
	}
	return YesNoSometimes.No;
	}

view raw gistfile1.d hosted with ❤ by GitHub

	mixin template QParse(string name, string defaultv, RET, ARGS...) if ((EnumMembers!RET).length-1 == ARGS.length) {
	mixin("""RET " ~ name ~ "(string text) {
	string[] stes = text.split(\",\");
	foreach(ste; stes) {
	switch(ste) {
	" ~ QParseGrabCases!(RET, ARGS) ~ "
	default:
	return RET." ~ defaultv ~ ";
	}
	}
	return RET." ~ defaultv ~ ";
	}""");
	}
	mixin template QParseOther(string name, RET, ARGS...) if ((EnumMembers!RET).length-1 == ARGS.length) {
	mixin("""RET " ~ name ~ "(string text, ref string other) {
	string[] stes = text.split(\",\");
	foreach(ste; stes) {
	switch(ste) {
	" ~ QParseGrabCases!(RET, ARGS) ~ "
	case \"Other\":
	continue;
	default:
	other = ste;
	return RET.Other;
	}
	}
	return RET.Other;
	}""");
	}
	pure string QParseGrabCases(RET, ARGS...)() {
	string ret;
	enum members = EnumMembers!RET;
	foreach(i, arg; ARGS) {
	ret ~= " case \"" ~ arg ~ "\":\n";
	ret ~= " return " ~ members[i].stringof ~ ";\n";
	}
	return ret;
	}
	mixin template QParseOtherBitwise(string name, RET, ARGS...) if ((EnumMembers!RET).length-2 == ARGS.length) {
	mixin("""size_t " ~ name ~ "(string text, ref string other) {
	size_t ret;
	string[] stes = text.split(\",\");
	foreach(ste; stes) {
	switch(ste) {
	" ~ QParseGrabCasesBitwise!(RET, ARGS) ~ "
	case \"Other\":
	continue;
	default:
	other = ste;
	ret |= RET.Other;
	break;
	}
	}
	return ret;
	}""");
	}
	pure string QParseGrabCasesBitwise(RET, ARGS...)() {
	string ret;
	enum members = (EnumMembers!RET)[1 .. $];
	foreach(i, arg; ARGS) {
	ret ~= " case \"" ~ arg ~ "\":\n";
	ret ~= " ret |= " ~ members[i].stringof ~ ";\n";
	ret ~= " break;\n";
	}
	return ret;
	}

view raw gistfile2.d hosted with ❤ by GitHub

Because I love templates, I created mixin templates called QParse, QParseOther and QParseOtherBitwise. These had "business rules" mixed in it e.g. a bitwised enum for RET must include None and Other in it.

Code like the top example could then be replaced by:

mixin QParseOther!("yesNoOther", YesNoOther, "Yes", "No");

One line instead of like 15 lines. I really don't feel like a code monkey anymore.

This blog post really does just show how much I love D's templates and compile time functionality.