Fix up Absolute value #abs (#491)

* Fix up Absolute value #abs
Defines #abs in Num
Implement #abs in UInt
Change #abs in SInt to return an SInt
Change #abs in FixedPoint to return a FixedPoint
Added  a couple of tests
Add some scala style suppression to Bits so I can read code in IntelliJ

* Per review
Add tests that abs works for positive values
Added SInt and UInt tests for abs to new underpopulated IntegerMathSpec
Used fixed point literals in fixed points abs definition

1 files changed, 33 insertions, 0 deletions

diff --git a/src/test/scala/chiselTests/IntegerMathSpec.scala b/src/test/scala/chiselTests/IntegerMathSpec.scala
new file mode 100644
index 00000000..3ccade8e
--- /dev/null
+++ b/src/test/scala/chiselTests/IntegerMathSpec.scala
@@ -0,0 +1,33 @@
+// See LICENSE for license details.
+
+package chiselTests
+
+import chisel3._
+import chisel3.testers.BasicTester
+
+//scalastyle:off magic.number
+class IntegerMathTester extends BasicTester {
+
+  //TODO: Add more operators
+
+  /* absolute values tests */
+
+  val uint = 3.U(4.W)
+  val sint = (-3).S()
+  val sintpos = 3.S()
+  val wrongSIntPos = 4.S()
+
+  assert(uint.abs() === uint)
+  assert(sint.abs() === sintpos)
+  assert(sintpos.abs() === sintpos)
+
+  assert(sint.abs() =/= wrongSIntPos)
+
+  stop()
+}
+
+class IntegerMathSpec extends ChiselPropSpec {
+  property("All integer ops should return the correct result") {
+    assertTesterPasses{ new IntegerMathTester }
+  }
+}