--- branches/vis12/src/compiler/fields/rational.sml	2012/07/07 04:35:18	1949
+++ branches/vis12/src/compiler/fields/rational.sml	2012/07/07 19:03:02	1950
@@ -37,6 +37,8 @@
     val <= : rat * rat -> bool
 *)
 
+    val isZero : rat -> bool
+
     val compare : rat * rat -> order
 
     val / : LargeInt.int * LargeInt.int -> rat
@@ -70,6 +72,8 @@
 
     val zero = R{num=0, denom=1}
 
+    fun isZero (R{num, ...}) = (num = 0)
+
     fun gcd (a : II.int, 0) = a
       | gcd (a, b) = if (a > b)
 	  then gcd(a-b, b)

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	<div class="error">does not end with &lt;/html&gt; tag</div>
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	<div class="info">The output has ended thus: = (num = 0)
+
     fun gcd (a : II.int, 0) = a
       | gcd (a, b) = if (a &gt; b)
 	  then gcd(a-b, b)</div>
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