2 files changed, 111 insertions, 2 deletions
diff --git a/clformat/src/main/java/bjc/utils/ioutils/format/CLFormatter.java b/clformat/src/main/java/bjc/utils/ioutils/format/CLFormatter.java
index 9263beb..db137a5 100644
--- a/clformat/src/main/java/bjc/utils/ioutils/format/CLFormatter.java
+++ b/clformat/src/main/java/bjc/utils/ioutils/format/CLFormatter.java
@@ -70,6 +70,8 @@ public class CLFormatter {
 		builtinDirectives.put("`[", new InflectDirective());
 
 		builtinDirectives.put("T", new TabulateDirective());
+
+		builtinDirectives.put("`D", new DecimalDirective());
 	}
 
 	/**
@@ -101,14 +103,32 @@ public class CLFormatter {
 	 */
 	public static void checkItem(Object itm, char directive) {
 		if (itm == null) {
-			String msg
-					= String.format("No argument provided for %c directive", directive);
+			String msg = String.format("No argument provided for %c directive", directive);
 
 			throw new IllegalArgumentException(msg);
 		}
 	}
 
 	/**
+	 * Check that an item is valid for a directive.
+	 *
+	 * @param itm
+	 *                  The item to check.
+	 *
+	 * @param directive
+	 *                  The directive to check for.
+	 *
+	 * @throws IllegalArgumentException
+	 *                                  if itm is null.
+	 */
+	public static void checkItem(Object itm, String directive) {
+		if (itm == null) {
+			String msg = String.format("No argument provided for %s directive", directive);
+
+			throw new IllegalArgumentException(msg);
+		}
+	}
+	/**
 	 * Format a string in the style of CL's FORMAT.
 	 *
 	 * @param format
diff --git a/clformat/src/main/java/bjc/utils/ioutils/format/directives/DecimalDirective.java b/clformat/src/main/java/bjc/utils/ioutils/format/directives/DecimalDirective.java
new file mode 100644
index 0000000..1130a85
--- /dev/null
+++ b/clformat/src/main/java/bjc/utils/ioutils/format/directives/DecimalDirective.java
@@ -0,0 +1,89 @@
+package bjc.utils.ioutils.format.directives;
+
+import java.io.*;
+import java.text.*;
+
+import bjc.esodata.*;
+import bjc.utils.ioutils.format.*;
+
+/**
+ * Implementation of the `D directive.
+ *
+ * This is the most general directive for printing out decimal-numbers (floating
+ * point).
+ *
+ * @author Ben Culkin
+ */
+public class DecimalDirective implements Directive {
+	@Override
+	public Edict compile(CompileContext compCTX) {
+		CLParameters params = compCTX.decr.parameters;
+		CLModifiers mods = compCTX.decr.modifiers;
+
+		CLValue decForm = CLValue.nil();
+
+		switch(params.length()) {
+		case 0:
+			// Use the default
+			break;
+		case 1:
+			// Use the specified format
+			params.mapIndices("format");
+
+			decForm = params.resolveKey("format");
+			break;
+		default:
+			// @TODO 16 Oct, 2020 - Ben Culkin - :Preformat
+			// Add ability to specify a common/fixed set of formats
+			//
+			// @TODO 16 Oct, 2020 - Ben Culkin - :ErrorFix
+			// Instead of using IllegalArgumentException here, use a custom
+			// subtype of it with an appropriate name/auto-message forming
+			throw new IllegalArgumentException("Must provide 0 or 1 arguments to `D directive");
+		}
+
+		return new DecimalEdict(decForm);
+	}
+}
+
+class DecimalEdict implements Edict {
+	private static final FieldPosition ZERO_FIELD = new FieldPosition(0);
+
+	private CLValue decFormat;
+
+	public DecimalEdict(CLValue decForm) {
+		this.decFormat = decForm;
+	}
+
+	@Override
+	public void format(FormatContext formCTX) throws IOException {
+		Tape<Object> itemTape = formCTX.items;
+
+		CLFormatter.checkItem(itemTape.item(), "`D");
+
+		NumberFormat numForm = NumberFormat.getInstance();
+
+		String decFormString = decFormat.getValue(itemTape);
+
+		if (decFormString == null || decFormString.equals("")) {
+			// Use the default if not provided.
+		} else {
+			if (numForm instanceof DecimalFormat) {
+				((DecimalFormat)numForm).applyPattern(decFormString);
+			} else {
+				String clsName = numForm.getClass().getName();
+
+				String msg = String.format("INTERNAL ERROR: Unknown NumberFormat type %s, expected DecimalFormat or compatible", clsName);
+
+				throw new UnsupportedOperationException(msg);
+			}
+		}
+
+		StringBuffer work = new StringBuffer();
+
+		numForm.format(itemTape.item(), work, ZERO_FIELD);
+
+		formCTX.writer.write(work.toString());
+		itemTape.right();
+	}
+}