vam: round() (#5598)

Author: mattnibs

runtime/sam/expr/function/math.go

@@ -139,9 +139,14 @@ type Round struct {
 func (r *Round) Call(_ super.Allocator, args []super.Value) super.Value {
 	val := args[0]
 	switch id := val.Type().ID(); {
+	case id == super.IDNull:
+		return val
 	case super.IsUnsigned(id) || super.IsSigned(id):
 		return val
 	case super.IsFloat(id):
+		if val.IsNull() {
+			return val
+		}
 		return super.NewFloat(val.Type(), math.Round(val.Float()))
 	}
 	return r.zctx.WrapError("round: not a number", val)

runtime/vam/expr/function/function.go

@@ -65,6 +65,8 @@ func New(zctx *super.Context, name string, narg int) (expr.Function, field.Path,
 	case "replace":
 		argmin, argmax = 3, 3
 		f = &Replace{zctx}
+	case "round":
+		f = &Round{zctx}
 	case "rune_len":
 		f = &RuneLen{zctx}
 	case "split":

runtime/vam/expr/function/math.go

@@ -179,6 +179,29 @@ func (l *Log) Call(args ...vector.Any) vector.Any {
 	return out
 }
 
+// https://github.com/brimdata/super/blob/main/docs/language/functions.md#round
+type Round struct {
+	zctx *super.Context
+}
+
+func (r *Round) Call(args ...vector.Any) vector.Any {
+	vec := args[0]
+	switch id := vec.Type().ID(); {
+	case id == super.IDNull:
+		return vec
+	case super.IsUnsigned(id) || super.IsSigned(id):
+		return vec
+	case super.IsFloat(id):
+		vals := make([]float64, vec.Len())
+		for i := range vec.Len() {
+			v, _ := vector.FloatValue(vec, i)
+			vals[i] = math.Round(v)
+		}
+		return vector.NewFloat(vec.Type(), vals, vector.NullsOf(vec))
+	}
+	return vector.NewWrappedError(r.zctx, "round: not a number", vec)
+}
+
 // https://github.com/brimdata/super/blob/main/docs/language/functions.md#sqrt
 type Sqrt struct {
 	zctx *super.Context

runtime/ztests/expr/function/round.yaml

@@ -0,0 +1,21 @@
+zed: "round(this)"
+
+vector: true
+
+input: |
+  -1
+  2(uint64)
+  1.5
+  2.4
+  null(float64)
+  null
+  "foo"
+
+output: |
+  -1
+  2(uint64)
+  2.
+  2.
+  null(float64)
+  null
+  error({message:"round: not a number",on:"foo"})