dmath: init directory

.gitignore

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 result
+.*.~undo-tree~
+*~

dmath/README.md

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+D programs that calculate various mathematical values
+
+## factors.d - calculate the factors of a number
+
+To work out the factors of 31:
+
+    ldc2 -run factors.d 31
+
+## isfactor.d - determine whether a number is a factor of another
+
+To determine whether 8 is a factor of 32:
+
+    ldc2 -run isfactor.d 8 32
+
+## hcf.d - calculate the highest common factor of two numbers
+
+To work out the HCF of 12 and 28:
+
+    ldc2 -run hcf.d 12 28
+
+To keep it simple this program will write out a list of factors
+for each number side-by-side.
+
+## lcm.d - calculate the lowest common multiple of two numbers
+
+To work out the LCM of 28 and 42:
+
+    ldc2 -run lcm.d 28 42
+
+To keep it simple this program will write out a list of multiples
+for each number side-by-side.
+
+## primes.d - generate a list of prime numbers up to a maximum value
+
+To generate a list of primes up to 100:
+
+    ldc2 -run primes.d
+
+If an argument is supplied, the program will calculate primes up to that number:
+
+    ldc2 -run primes.d 10
+
+(outputs 2, 3, 5, and 7)
+Two arguments can be supplied to specify a minimum as well:
+
+    ldc2 -run primes.d 1 20
+
+(outputs primes from 1 to 20)

dmath/factors.d

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+import std.conv : to;
+import std.stdio : stderr, write, writeln;
+
+int
+main(string[] args)
+{
+	int n;
+
+	if (args.length == 1) {
+		stderr.writeln("usage: factors.d number");
+		return 1;
+	}
+
+	n = args[1].to!int();
+	foreach (int factor; factorsOf(n)) {
+		writeln(factor);
+	}
+
+	return 0;
+}
+
+int[]
+factorsOf(int x)
+{
+	int[] a;
+
+	foreach (int i; 1 .. x + 1) {
+		if (x % i == 0)
+			a ~= i;
+	}
+
+	return a;
+}

dmath/hcf.d

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+import std.conv : to;
+import std.stdio : write, writeln;
+
+void
+main(string[] args)
+{
+	int i, x, y;
+	int[] xf, yf;
+
+	x = args[1].to!int();
+	y = args[2].to!int();
+
+	xf = factorsOf(x);
+	yf = factorsOf(y);
+	for (i = 0; xf.length > i || yf.length > i; i++) {
+		if (i < xf.length)
+			write(xf[i]);
+		write("	");
+		if (i < yf.length)
+			write(yf[i]);
+		writeln();
+	}
+}
+
+int[]
+factorsOf(int x)
+{
+	int[] a;
+
+	foreach (int i; 1 .. x + 1) {
+		if (x % i == 0)
+			a ~= i;
+	}
+
+	return a;
+}

dmath/isfactor.d

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+import std.conv : to;
+import std.stdio : stderr, writeln;
+
+int
+main(string[] args)
+{
+	int f, i, n;
+
+	if (args.length < 3) {
+		stderr.writeln("usage: isfactor.d fac num");
+		return 1;
+	}
+
+	f = args[1].to!int();
+	n = args[2].to!int();
+
+	i = f;
+	while (i < n) {
+		i += f;
+	}
+
+	if (i == n) {
+		writeln(f, " is a factor of ", n);
+		return 0;
+	}
+
+	writeln(f, " is NOT a factor of ", n);
+	return 1;
+}

dmath/lcm.d

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+import std.conv : to;
+import std.stdio : writeln;
+
+void
+main(string[] args)
+{
+	int x, y;
+
+	x = args[1].to!int();
+	y = args[2].to!int();
+
+	foreach (int i; 1 .. 12) {
+		writeln(x * i, "	", y * i);
+	}
+}

dmath/primes.d

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+import std.conv : to;
+import std.stdio : write, writeln;
+
+void
+main(string[] args)
+{
+	int min, max;
+
+	min = 1;
+	max = 100;
+
+	if (args.length == 2) {
+		max = args[1].to!int();
+	}
+	if (args.length == 3) {
+		min = args[1].to!int();
+		max = args[2].to!int();
+	}
+
+	foreach (int i; min .. max + 1) {
+		if (factorsOf(i).length == 2)
+			writeln(i);
+	}
+}
+
+int[]
+factorsOf(int x)
+{
+	int[] a;
+
+	foreach (int i; 1 .. x + 1) {
+		if (x % i == 0)
+			a ~= i;
+	}
+
+	return a;
+}