Merge pull request #21 from PetrPytelka/improved_round_function

Round function was extended with optional parameter numdecimalplaces

Author: verhas

src/main/java/com/scriptbasic/utility/functions/MathFunctions.java

@@ -1,5 +1,9 @@
 package com.scriptbasic.utility.functions;
 
+import java.math.BigDecimal;
+import java.math.MathContext;
+import java.math.RoundingMode;
+
 import com.scriptbasic.api.BasicFunction;
 import com.scriptbasic.api.ScriptBasicException;
 import com.scriptbasic.interfaces.BasicRuntimeException;
@@ -21,6 +25,11 @@
 @SuppressWarnings({"SameReturnValue", "UnusedReturnValue"})
 public class MathFunctions {
 
+    /**
+     * Rounding mode used by round function
+     */
+    static public RoundingMode roundingMode = RoundingMode.HALF_EVEN;
+
     private MathFunctions() {
         NoInstance.isPossible();
     }
@@ -216,9 +225,28 @@ public static double rint(final double a) {
         return 0.0;
     }
 
-    @BasicFunction(substituteClass = java.lang.Math.class, classification = com.scriptbasic.classification.Math.class)
-    static public double round(final double x) {
-        return 0.0;
+    /**
+     * Returns a number rounded to a specified number of decimal places.
+     * 
+     * This function returns something commonly referred to as bankers rounding. 
+     * So be careful before using this function. Same behavior has 'round' in VBA.
+     * 
+     * @param value Numeric value being rounded
+     * @param numdecimalplaces Number indicating how many places to the right of the decimal 
+     *        are included in the rounding.
+     * @return rounded value
+     */
+    @BasicFunction(classification = com.scriptbasic.classification.Math.class)
+    static public Number round(final double value, Integer numdecimalplaces) {
+        
+        final BigDecimal bd = BigDecimal.valueOf(value);
+
+        if (numdecimalplaces == null || numdecimalplaces == 0) {
+            return bd.setScale(0, roundingMode).intValue();
+        } else {
+            final MathContext mc = new MathContext(numdecimalplaces, roundingMode);
+            return bd.round(mc).doubleValue();
+        }
     }
 
     @BasicFunction(substituteClass = java.lang.Math.class, classification = com.scriptbasic.classification.Math.class)

src/test/java/com/scriptbasic/test/auxilliary/TestMathFunctions.java

@@ -87,7 +87,7 @@ public void testExMethods() throws
 
         pow(x, y);
 
-        round(x);
+        round(x, 0);
 
         tan(x);
 

src/test/resources/com/scriptbasic/testprograms/TestMath.bas

@@ -6,4 +6,8 @@ assert("cos(0)=1", cos(0.0)=1.0)
 assert("sin(0)=0", sin(0.0)=0.0)
 assert("acos(1.0)=0", acos(1.0)=0.0)
 assert("asin(0)=0",asin(0.0)=0.0)
-assert("strrev",strreverse("abc")="cba")
+assert("round0_5",round(0.5)=0)
+assert("round1_5",round(1.5)=2)
+assert("round0_14",round(0.14,1)=0.1)
+assert("round0_15",round(0.15,1)=0.2)
+assert("round0_16",round(0.16,1)=0.2)

src/test/resources/com/scriptbasic/testprograms/TestStringFunctions.bas

@@ -2,3 +2,5 @@ v = "0123456789"
 PRINT left(v,2)
 PRINT RIGHT(v,2)
 PRINT Mid(v,2,3)
+
+assert("strrev",strreverse("abc")="cba")