Add support for the Round() functional operator.

PiperOrigin-RevId: 677032631

interpreter/operator_arithmetic.go

@@ -603,6 +603,55 @@ func evalNegateQuantity(m model.IUnaryExpression, obj result.Value) (result.Valu
 	return result.New(val)
 }
 
+// Round(argument Decimal) Decimal
+// Round(argument Decimal, argument Integer) Decimal
+// https://cql.hl7.org/09-b-cqlreference.html#round
+// If a precision is specified but is null then the default precision is 0.
+// If a precision is specified but is negative then an error is returned. This is technically
+// undefined behavior in the CQL spec, but we choose to throw an error here.
+func evalRound(_ model.INaryExpression, operands []result.Value) (result.Value, error) {
+	// if len(operands) == 1 {
+	// 	return roundValue(operands[0])
+	// }
+	decimalVal := operands[0]
+	var precisionVal result.Value
+	var err error
+	// retrieve the precision if it exists, otherwise default to 0.
+	if len(operands) == 2 {
+		precisionVal = operands[1]
+	} else {
+		precisionVal, err = result.New(0)
+		if err != nil {
+			return result.Value{}, err
+		}
+	}
+	if result.IsNull(decimalVal) {
+		return result.New(nil)
+	}
+
+	p, err := result.ToInt32(precisionVal)
+	if err != nil {
+		p = 0
+	}
+	if p < 0 {
+		return result.Value{}, fmt.Errorf("internal error - precision must be non-negative, got %v", p)
+	}
+	d, err := result.ToFloat64(decimalVal)
+	if err != nil {
+		return result.Value{}, err
+	}
+	ratio := math.Pow10(int(p))
+	// CQL currently implements its own special version of rounding for now (which will be changed in
+	// the future). For now if the value is negative we round towards zero.
+	ratioedDecimal := d * ratio
+	_, frac := math.Modf(ratioedDecimal)
+	if frac == -0.5 {
+		// force go to round towards zero
+		ratioedDecimal += 0.1
+	}
+	return result.New(math.Round(ratioedDecimal) / ratio)
+}
+
 // predecessor of<T>(obj T) T
 // https://cql.hl7.org/09-b-cqlreference.html#predecessor
 func (i *interpreter) evalPredecessor(m model.IUnaryExpression, obj result.Value) (result.Value, error) {

interpreter/operator_dispatcher.go

@@ -1049,6 +1049,17 @@ func (i *interpreter) naryOverloads(m model.INaryExpression) ([]convert.Overload
 				Result:   i.evalCombine,
 			},
 		}, nil
+	case *model.Round:
+		return []convert.Overload[evalNarySignature]{
+			{
+				Operands: []types.IType{types.Decimal},
+				Result:   evalRound,
+			},
+			{
+				Operands: []types.IType{types.Decimal, types.Integer},
+				Result:   evalRound,
+			},
+		}, nil
 	default:
 		return nil, fmt.Errorf("unsupported Nary Expression %v", m.GetName())
 	}

model/model.go

@@ -1067,6 +1067,9 @@ type DateTime struct{ *NaryExpression }
 // one of those at that point.
 type Now struct{ *NaryExpression }
 
+// Round ELM Expression https://cql.hl7.org/04-logicalspecification.html#round
+type Round struct{ *NaryExpression }
+
 // TimeOfDay is https://cql.hl7.org/04-logicalspecification.html#timeofday
 // Note: in the future we may implement the OperatorExpression, and should convert this to
 // one of those at that point.
@@ -1325,6 +1328,9 @@ func (a *Modulo) GetName() string { return "Modulo" }
 // GetName returns the name of the system operator.
 func (a *Power) GetName() string { return "Power" }
 
+// GetName returns the name of the system operator.
+func (a *Round) GetName() string { return "Round" }
+
 // GetName returns the name of the system operator.
 func (a *TruncatedDivide) GetName() string { return "TruncatedDivide" }
 

parser/operators.go

@@ -19,10 +19,10 @@ import (
 	"fmt"
 	"strings"
 
-	"github.com/antlr4-go/antlr/v4"
 	"github.com/google/cql/internal/convert"
 	"github.com/google/cql/model"
 	"github.com/google/cql/types"
+	"github.com/antlr4-go/antlr/v4"
 )
 
 // parseFunction uses the reference resolver to resolve the function, visits the operands, and sets
@@ -881,6 +881,28 @@ func (p *Parser) loadSystemOperators() error {
 				}
 			},
 		},
+		{
+			name:     "Round",
+			operands: [][]types.IType{{types.Decimal, types.Integer}},
+			model: func() model.IExpression {
+				return &model.Round{
+					NaryExpression: &model.NaryExpression{
+						Expression: model.ResultType(types.Decimal),
+					},
+				}
+			},
+		},
+		{
+			name:     "Round",
+			operands: [][]types.IType{{types.Decimal}},
+			model: func() model.IExpression {
+				return &model.Round{
+					NaryExpression: &model.NaryExpression{
+						Expression: model.ResultType(types.Decimal),
+					},
+				}
+			},
+		},
 		{
 			name: "Successor",
 			operands: [][]types.IType{

parser/operators_test.go

@@ -615,6 +615,31 @@ func TestBuiltInFunctions(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "Round 1.42",
+			cql:  "Round(1.42)",
+			want: &model.Round{
+				NaryExpression: &model.NaryExpression{
+					Operands: []model.IExpression{
+						model.NewLiteral("1.42", types.Decimal),
+					},
+					Expression: model.ResultType(types.Decimal),
+				},
+			},
+		},
+		{
+			name: "Round 3.14159 to 3 decimal places",
+			cql:  "Round(3.14159, 3)",
+			want: &model.Round{
+				NaryExpression: &model.NaryExpression{
+					Operands: []model.IExpression{
+						model.NewLiteral("3.14159", types.Decimal),
+						model.NewLiteral("3", types.Integer),
+					},
+					Expression: model.ResultType(types.Decimal),
+				},
+			},
+		},
 		{
 			name: "Predecessor for Date",
 			cql:  "Predecessor(@2023)",

tests/enginetests/operator_arithmetic_test.go

@@ -973,6 +973,147 @@ func TestMultiply(t *testing.T) {
 	}
 }
 
+func TestRound(t *testing.T) {
+	tests := []struct {
+		name       string
+		cql        string
+		wantModel  model.IExpression
+		wantResult result.Value
+	}{
+		{
+			name:       "Simple",
+			cql:        "Round(42.101)",
+			wantResult: newOrFatal(t, 42.0),
+		},
+		{
+			name:       "Negative decimal",
+			cql:        "Round(-101.42)",
+			wantResult: newOrFatal(t, -101.0),
+		},
+		{
+			name: "Integers",
+			cql:  "Round(2)",
+			wantModel: &model.Round{
+				NaryExpression: &model.NaryExpression{
+					Operands: []model.IExpression{
+						&model.ToDecimal{
+							UnaryExpression: &model.UnaryExpression{
+								Operand:    model.NewLiteral("2", types.Integer),
+								Expression: model.ResultType(types.Decimal),
+							},
+						},
+					},
+					Expression: model.ResultType(types.Decimal),
+				},
+			},
+			wantResult: newOrFatal(t, 2.0),
+		},
+		{
+			name:       "Negative, round up",
+			cql:        "Round(-0.5)",
+			wantResult: newOrFatal(t, 0.0),
+		},
+		{
+			name:       "Negative, round down",
+			cql:        "Round(-0.6)",
+			wantResult: newOrFatal(t, -1.0),
+		},
+		{
+			name:       "Zero",
+			cql:        "Round(0.0)",
+			wantResult: newOrFatal(t, 0.0),
+		},
+		{
+			name:       "Null",
+			cql:        "Round(null as Decimal)",
+			wantResult: newOrFatal(t, nil),
+		},
+		// With precision
+		{
+			name:       "Simple with precision",
+			cql:        "Round(42.101, 1)",
+			wantResult: newOrFatal(t, 42.1),
+		},
+		{
+			name:       "Negative decimal with precision round up",
+			cql:        "Round(-101.45, 1)",
+			wantResult: newOrFatal(t, -101.4),
+		},
+		{
+			name:       "Negative decimal with precision round down",
+			cql:        "Round(-101.46, 1)",
+			wantResult: newOrFatal(t, -101.5),
+		},
+		{
+			name:       "Precision is 0",
+			cql:        "Round(2.123, 0)",
+			wantResult: newOrFatal(t, 2.0),
+		},
+		{
+			name:       "Precision is null",
+			cql:        "Round(2.123, null)",
+			wantResult: newOrFatal(t, 2.0),
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			p := newFHIRParser(t)
+			parsedLibs, err := p.Libraries(context.Background(), wrapInLib(t, tc.cql), parser.Config{})
+			if err != nil {
+				t.Fatalf("Parse returned unexpected error: %v", err)
+			}
+			if diff := cmp.Diff(tc.wantModel, getTESTRESULTModel(t, parsedLibs)); tc.wantModel != nil && diff != "" {
+				t.Errorf("Parse diff (-want +got):\n%s", diff)
+			}
+
+			results, err := interpreter.Eval(context.Background(), parsedLibs, defaultInterpreterConfig(t, p))
+			if err != nil {
+				t.Fatalf("Eval returned unexpected error: %v", err)
+			}
+			if diff := cmp.Diff(tc.wantResult, getTESTRESULT(t, results), protocmp.Transform()); diff != "" {
+				t.Errorf("Eval diff (-want +got)\n%v", diff)
+			}
+		})
+	}
+}
+
+func TestRound_EvalErrors(t *testing.T) {
+	tests := []struct {
+		name                string
+		cql                 string
+		wantModel           model.IExpression
+		wantEvalErrContains string
+	}{
+		{
+			name:                "Round with a negative precision",
+			cql:                 "Round(2.123, -1)",
+			wantEvalErrContains: "precision must be non-negative",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			p := newFHIRParser(t)
+			parsedLibs, err := p.Libraries(context.Background(), wrapInLib(t, tc.cql), parser.Config{})
+			if err != nil {
+				t.Fatalf("Parse returned unexpected error: %v", err)
+			}
+			if diff := cmp.Diff(tc.wantModel, getTESTRESULTModel(t, parsedLibs)); tc.wantModel != nil && diff != "" {
+				t.Errorf("Parse diff (-want +got):\n%s", diff)
+			}
+
+			_, err = interpreter.Eval(context.Background(), parsedLibs, defaultInterpreterConfig(t, p))
+			if err == nil {
+				t.Fatalf("Evaluate Expression expected an error to be returned, got nil instead")
+			}
+			if !strings.Contains(err.Error(), tc.wantEvalErrContains) {
+				t.Errorf("Unexpected evaluation error contents got (%v) want (%v)", err.Error(), tc.wantEvalErrContains)
+			}
+		})
+	}
+}
+
 func TestTruncate(t *testing.T) {
 	tests := []struct {
 		name       string

tests/spectests/exclusions/exclusions.go

@@ -60,17 +60,11 @@ func XMLTestFileExclusionDefinitions() map[string]XMLTestFileExclusions {
 				"HighBoundary",
 				"Log",
 				"LowBoundary",
-				"Round",
 			},
 			NamesExcludes: []string{
 				// TODO: b/342061715 - Unsupported operator.
-				"Divide103",
 				"Multiply1CMBy2CM",
 				"Power2DToNeg2DEquivalence",
-				"Exp1",    // Require Round support.
-				"ExpNeg1", // Require Round support.
-				"Ln1000",  // Require Round support.
-				"Ln1000D", // Require Round support.
 				// TODO: b/342061606 - Unit conversion is not supported.
 				"Divide1Q1",
 				"Divide10Q5I",