MLKFloat: Explicitly declare the contract for subclasses.

2 files changed, 42 insertions, 2 deletions

diff --git a/MLKFloat.h b/MLKFloat.h
index fe9ed48..bd8c3e4 100644
--- a/MLKFloat.h
+++ b/MLKFloat.h
@@ -20,7 +20,12 @@
 
 #import <Foundation/NSString.h>
 
-
+// An MLKFloat can represent any kind of CL floating-point number.
+//
+// MLKFloat itself is not instantiable.  It is a class cluster whose
+// instances are of one of its subclasses (currently MLKSingleFloat und
+// MLKDoubleFloat; an arbitrary-precision, GMP-backed type is planned
+// for the future).
 @interface MLKFloat : MLKLispValue
 +(MLKFloat *) floatWithExponentMarker:(unichar)exponentMarker
                           integerPart:(NSString *)intPart
@@ -28,4 +33,15 @@
                        fractionalPart:(NSString *)fractPart
                              exponent:(NSString *)exponent
                      exponentNegative:(BOOL)exponentNegative;
+
+// Abstract methods.
+-(float) floatValue;
+-(double) doubleValue;
+
+-(MLKFloat *) add:(MLKFloat *)arg;
+-(MLKFloat *) subtract:(MLKFloat *)arg;
+-(MLKFloat *) multiplyWith:(MLKFloat *)arg;
+-(MLKFloat *) divideBy:(MLKFloat *)arg;
+
+-(NSString *) description;
 @end
diff --git a/MLKFloat.m b/MLKFloat.m
index 4083146..4fc2144 100644
--- a/MLKFloat.m
+++ b/MLKFloat.m
@@ -21,6 +21,7 @@
 #import "MLKDoubleFloat.h"
 #import "MLKPackage.h"
 #import "MLKDynamicContext.h"
+#import "MLKError.h"
 
 
 @implementation MLKFloat : MLKLispValue
@@ -32,9 +33,13 @@
                      exponentNegative:(BOOL)exponentNegative
 {
   MLKSymbol *defaultFormat;
-  MLKPackage *cl = [MLKPackage findPackage:@"COMMON-LISP"];
+  MLKPackage *cl;
+
+  cl = [MLKPackage findPackage:@"COMMON-LISP"];
   defaultFormat = [[MLKDynamicContext currentContext]
                     valueForBinding:[cl intern:@"*READ-DEFAULT-FLOAT-FORMAT*"]];
+
+  // FIXME: Shouldn't the readtable decide which exponent markers do what?
   if (exponentMarker == 'd' || exponentMarker == 'D'
       || exponentMarker == 'l' || exponentMarker == 'L'
       || ((exponentMarker == 'e' || exponentMarker == 'E')
@@ -52,4 +57,23 @@
                            exponent:exponent
                            exponentNegative:exponentNegative];
 }
+
+#define DECLARE_ABSTRACT(SIGNATURE, RETURN_VALUE)                       \
+  SIGNATURE                                                             \
+  {                                                                     \
+    [[MLKError errorWithMessage:@"Tried to invoke an abstract method."] raise]; \
+    return RETURN_VALUE;                                                \
+  }
+
+DECLARE_ABSTRACT (-(float) floatValue, 0.0)
+DECLARE_ABSTRACT (-(double) doubleValue, 0.0)
+DECLARE_ABSTRACT (-(MLKFloat *) add:(MLKFloat *)arg, nil)
+DECLARE_ABSTRACT (-(MLKFloat *) subtract:(MLKFloat *)arg, nil)
+DECLARE_ABSTRACT (-(MLKFloat *) multiplyWith:(MLKFloat *)arg, nil)
+DECLARE_ABSTRACT (-(MLKFloat *) divideBy:(MLKFloat *)arg, nil)
+
+-(NSString *) description
+{
+  return [super description];
+}
 @end