For as builtin and new example that plays primes

examples/arithmetic.mq

@@ -1,3 +0,0 @@
-say (1 + 3);
-say (3 * 10);
-say 42

examples/arrays.mq

@@ -1,11 +0,0 @@
-var numbers = [1;2;3;4;5];
-
-var for = [array iteration |
-	var iter = [i | if (i < (len array)) [
-		iteration (numbers.i);
-		iter (i+1)
-	]];
-	iter 0
-];
-
-for numbers say;

examples/rhythm-of-primes.mq

@@ -0,0 +1,16 @@
+------------------------------------------------------------
+Inspired by Marc Evanstein video "The Rythm of The Primes"
+Link: https://www.youtube.com/watch?v=8x374slJGuo
+------------------------------------------------------------
+
+var Length = 20;
+
+var cmajor = [c;d;e;f;g];
+var scale = reverse cmajor;
+var primes = nprimes (len scale);
+var indicies = up (len scale);
+
+oct 3;
+len (1/16);
+
+for (2 + up Length) [ i | play (chord scale.(indicies.(i % primes == 0))); ];

src/builtin_functions.cc

@@ -349,7 +349,7 @@ static Result<Value> builtin_primes(Interpreter&, std::vector<Value> args)
 	return Error {
 		.details = errors::Unsupported_Types_For {
 			.type = errors::Unsupported_Types_For::Function,
-			.name = "primes",
+			.name = "nprimes",
 			.possibilities = {
 				"(number) -> array of number"
 			}
@@ -357,6 +357,18 @@ static Result<Value> builtin_primes(Interpreter&, std::vector<Value> args)
 	};
 }
 
+static Result<Value> builtin_for(Interpreter &i, std::vector<Value> args)
+{
+	if (is_indexable(args[0].type)) {
+		for (size_t n = 0; n < args[0].size(); ++n) {
+			Try(args[1](i, { Try(args[0].index(i, n)) }));
+		}
+		return Value{};
+	}
+
+	unimplemented();
+}
+
 void Interpreter::register_builtin_functions()
 {
 	auto &global = *Env::global;
@@ -609,5 +621,6 @@ error:
 	global.force_define("up",    builtin_range<Range_Direction::Up>);
 	global.force_define("down",  builtin_range<Range_Direction::Down>);
 
-	global.force_define("primes", builtin_primes);
+	global.force_define("nprimes", builtin_primes);
+	global.force_define("for", builtin_for);
 }