fix setting an invalid epsilon

Setting an invalid epsilon via the epsilon(value) or confiv("epsilon",
value) triggers an error.  The epsilon value must be: 0 < epsilon < 1.

CHANGES

@@ -86,6 +86,9 @@ The following are the changes from calc version 2.14.3.5 to date:
     The len element in a ZVALUE is of type LEN.  LEN type is SB32 when
     MAJOR_VER < 3, or a uintptr_t otherwise.
 
+    Setting an invalid epsilon via the epsilon(value) or confiv("epsilon",
+    value) triggers an error.  The epsilon value must be: 0 < epsilon < 1.
+
 
 The following are the changes from calc version 2.14.3.4 to 2.14.3.5:
 

qfunc.c

@@ -43,6 +43,29 @@ STATIC long E_num;
 
 #define QALLOCNUM 64
 
+
+/*
+ * verify_epsilon - verify that 0 < epsilon < 1
+ *
+ * This function is called via the OP_SETEPSILON op code, config("epsilon",
+ * and from various builtin functions that take an epsilon argument.
+ *
+ * If all is well, this function just returns.  If the arg passed is
+ * out of range, then a math_error() is triggered causing this function
+ * to not return.
+ */
+void
+verify_epsilon(NUMBER *q)
+{
+	/* verify that 0 < epsilon < 1 */
+	if (q == NULL || qisneg(q) || qiszero(q) || qisone(q) || qreli(q, 1) > 0) {
+		math_error("Invalid value for epsilon: must be: 0 < epsilon < 1");
+		not_reached();
+	}
+	return;
+}
+
+
 /*
  * Set the default epsilon for approximate calculations.
  * This must be greater than zero.
@@ -55,10 +78,7 @@ setepsilon(NUMBER *q)
 {
 	NUMBER *old;
 
-	if (qisneg(q) || qiszero(q)) {
-		math_error("Epsilon value must be greater than zero");
-		not_reached();
-	}
+	verify_epsilon(q);
 	old = conf->epsilon;
 	conf->epsilonprec = qprecision(q);
 	conf->epsilon = qlink(q);

qmath.h

@@ -167,6 +167,7 @@ E_FUNC long qprecision(NUMBER *q);
 E_FUNC long qplaces(NUMBER *q, ZVALUE base);
 E_FUNC long qdecplaces(NUMBER *q);
 E_FUNC long qdigits(NUMBER *q, ZVALUE base);
+E_FUNC void verify_epsilon(NUMBER *q);
 E_FUNC void setepsilon(NUMBER *q);
 E_FUNC NUMBER *qbitvalue(long i);
 E_FUNC NUMBER *qtenpow(long i);