Bug 1275043

3 files changed, 103 insertions, 11 deletions

diff --git a/ChangeLog b/ChangeLog
index 5ed5e36..7127890 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2005-08-29  Kevin Kenny  <kennykb@acm.org>
+
+	* generic/tclBasic.c (ExprMathFunc): Restored "round away from
+	* tests/expr.test (expr-39.*):       zero" behaviour to the
+	                                     "round" function.  Added 
+	test cases for the behavior, including the awkward case of a
+	number whose fractional part is 1/2-1/2ulp. [Bug 1275043]
+	
 2005-08-25  Donal K. Fellows  <donal.k.fellows@man.ac.uk>
 
 	* generic/tclListObj.c (UpdateStringOfList): Stop uncontrolled and
diff --git a/generic/tclExecute.c b/generic/tclExecute.c
index 82aaf62..5161b17 100644
--- a/generic/tclExecute.c
+++ b/generic/tclExecute.c
@@ -11,7 +11,7 @@
  * See the file "license.terms" for information on usage and redistribution
  * of this file, and for a DISCLAIMER OF ALL WARRANTIES.
  *
- * RCS: @(#) $Id: tclExecute.c,v 1.94.2.13 2005/08/05 19:19:11 kennykb Exp $
+ * RCS: @(#) $Id: tclExecute.c,v 1.94.2.14 2005/08/29 16:37:42 kennykb Exp $
  */
 
 #include "tclInt.h"
@@ -5462,7 +5462,7 @@ ExprRoundFunc(interp, eePtr, clientData)
     Tcl_Obj **stackPtr;        /* Cached evaluation stack base pointer. */
     register int stackTop;	/* Cached top index of evaluation stack. */
     Tcl_Obj *valuePtr, *resPtr;
-    double d;
+    double d, f, i;
     int result;
 
     /*
@@ -5488,22 +5488,35 @@ ExprRoundFunc(interp, eePtr, clientData)
 	result = TCL_OK;
 	resPtr = valuePtr;
     } else {
+
+	/* 
+	 * Round the number to the nearest integer.  I'd like to use round(),
+	 * but it's C99 (or BSD), and not yet universal.
+	 */
+	
 	d = valuePtr->internalRep.doubleValue;
+	f = modf(d, &i);
 	if (d < 0.0) {
-	    if (d <= Tcl_WideAsDouble(LLONG_MIN)-0.5) {
+	    if (f <= -0.5) {
+		i += -1.0;
+	    }
+	    if (i <= Tcl_WideAsDouble(LLONG_MIN)) {
 		goto tooLarge;
-	    } else if (d <= (((double) (long) LONG_MIN) - 0.5)) {
-		resPtr = Tcl_NewWideIntObj(Tcl_DoubleAsWide(d - 0.5));
+	    } else if (d <= (double) LONG_MIN) {
+		resPtr = Tcl_NewWideIntObj(Tcl_DoubleAsWide(i));
 	    } else {
-		resPtr = Tcl_NewLongObj((long) (d - 0.5));
+		resPtr = Tcl_NewLongObj((long) i);
 	    }			    
 	} else {
-	    if (d >= Tcl_WideAsDouble(LLONG_MAX)+0.5) {
+	    if (f >= 0.5) {
+		i += 1.0;
+	    }
+	    if (i >= Tcl_WideAsDouble(LLONG_MAX)) {
 		goto tooLarge;
-	    } else if (d >= (((double) LONG_MAX + 0.5))) {
-		resPtr = Tcl_NewWideIntObj(Tcl_DoubleAsWide(d + 0.5));
+	    } else if (i >= (double) LONG_MAX) {
+		resPtr = Tcl_NewWideIntObj(Tcl_DoubleAsWide(i));
 	    } else {
-		resPtr = Tcl_NewLongObj((long) (d + 0.5));
+		resPtr = Tcl_NewLongObj((long) i);
 	    }
 	}
     }
diff --git a/tests/expr.test b/tests/expr.test
index b3707b8..af9b55c 100644
--- a/tests/expr.test
+++ b/tests/expr.test
@@ -10,7 +10,7 @@
 # See the file "license.terms" for information on usage and redistribution
 # of this file, and for a DISCLAIMER OF ALL WARRANTIES.
 #
-# RCS: @(#) $Id: expr.test,v 1.17.2.5 2005/08/05 19:19:14 kennykb Exp $
+# RCS: @(#) $Id: expr.test,v 1.17.2.6 2005/08/29 16:37:45 kennykb Exp $
 
 if {[lsearch [namespace children] ::tcltest] == -1} {
     package require tcltest
@@ -827,6 +827,77 @@ test expr-38.1 {abs of smallest 32-bit integer [Bug 1241572]} {wideIs64bit} {
     expr {abs(int(-2147483648))}
 } 2147483648
 
+test expr-39.1 {round() rounds to +-infinity} {
+    expr round(0.5)
+} 1
+test expr-39.2 {round() rounds to +-infinity} {
+    expr round(1.5)
+} 2
+test expr-39.3 {round() rounds to +-infinity} {
+    expr round(-0.5)
+} -1
+test expr-39.4 {round() rounds to +-infinity} {
+    expr round(-1.5)
+} -2
+test expr-39.5 {round() overflow} {
+    list [catch {expr round(9.2233720368547758e+018)} result] $result
+} {1 {integer value too large to represent}}
+test expr-39.6 {round() overflow} {
+    list [catch {expr round(-9.2233720368547758e+018)} result] $result
+} {1 {integer value too large to represent}}
+test expr-39.7 {round() bad value} {
+    set x trash
+    list [catch {expr {round($x)}} result] $result
+} {1 {argument to math function didn't have numeric value}}
+test expr-39.8 {round() already an integer} {
+    set x 123456789012
+    incr x
+    expr round($x)
+} 123456789013
+test expr-39.9 {round() boundary case - 1/2 - 1 ulp} {
+    set x 0.25
+    set bit 0.125
+    while 1 {
+	set newx [expr {$x + $bit}]
+	if { $newx == $x || $newx == 0.5 } break
+	set x $newx
+	set bit [expr { $bit / 2.0 }]
+    }
+    expr {round($x)}
+} 0
+test expr-39.10 {round() boundary case - 1/2 + 1 ulp} {
+    set x 0.75
+    set bit 0.125
+    while 1 {
+	set newx [expr { $x - $bit }]
+	if { $newx == $x || $newx == 0.5 } break
+	set x $newx
+	set bit [expr { $bit / 2.0 }]
+    }
+    expr {round($x)}
+} 1
+test expr-39.11 {round() boundary case - -1/2 - 1 ulp} {
+    set x -0.75
+    set bit 0.125
+    while 1 {
+	set newx [expr { $x + $bit }]
+	if { $newx == $x || $newx == -0.5 } break
+	set x $newx
+	set bit [expr { $bit / 2.0 }]
+    }
+    expr {round($x)}
+} -1
+test expr-39.10 {round() boundary case - -1/2 + 1 ulp} {
+    set x -0.25
+    set bit 0.125
+    while 1 {
+	set newx [expr { $x - $bit }]
+	if { $newx == $x || $newx == -0.5 } break
+	set x $newx
+	set bit [expr { $bit / 2.0 }]
+    }
+    expr {round($x)}
+} 0
 
 # cleanup
 if {[info exists a]} {