Add support for Precision() functional operator.

interpreter/operator_arithmetic.go

@@ -300,6 +300,63 @@ func arithmetic[t float64 | int64 | int32](m model.IBinaryExpression, l, r t) (r
 	return result.Value{}, fmt.Errorf("internal error - unsupported Binary Arithmetic Expression %v", m)
 }
 
+// Precision(arg Date) Integer
+// Precision(arg DateTime) Integer
+// https://cql.hl7.org/09-b-cqlreference.html#precision
+// TODO: b/301606416 - Precision for Decimals is not yet supported due to needing to handle
+// trailing zeros.
+func evalPrecisionDateTime(_ model.IUnaryExpression, obj result.Value) (result.Value, error) {
+	if result.IsNull(obj) {
+		return result.New(nil)
+	}
+	dt, err := result.ToDateTime(obj)
+	if err != nil {
+		return result.Value{}, err
+	}
+	switch dt.Precision {
+	case model.YEAR:
+		return result.New(4)
+	case model.MONTH:
+		return result.New(6)
+	case model.DAY:
+		return result.New(8)
+	case model.HOUR:
+		return result.New(10)
+	case model.MINUTE:
+		return result.New(12)
+	case model.SECOND:
+		return result.New(14)
+	case model.MILLISECOND:
+		return result.New(17)
+	default:
+		return result.Value{}, fmt.Errorf("internal error - unsupported DateTime precision %v", dt.Precision)
+	}
+}
+
+// Precision(arg Time) Integer
+// https://cql.hl7.org/09-b-cqlreference.html#precision
+func evalPrecisionTime(_ model.IUnaryExpression, obj result.Value) (result.Value, error) {
+	if result.IsNull(obj) {
+		return result.New(nil)
+	}
+	dt, err := result.ToDateTime(obj)
+	if err != nil {
+		return result.Value{}, err
+	}
+	switch dt.Precision {
+	case model.HOUR:
+		return result.New(2)
+	case model.MINUTE:
+		return result.New(4)
+	case model.SECOND:
+		return result.New(6)
+	case model.MILLISECOND:
+		return result.New(9)
+	default:
+		return result.Value{}, fmt.Errorf("internal error - unsupported Time precision %v", dt.Precision)
+	}
+}
+
 // ^(left Integer, right Integer) Integer
 // ^(left Long, right Long) Long
 // ^(left Decimal, right Decimal) Decimal

interpreter/operator_dispatcher.go

@@ -157,6 +157,21 @@ func (i *interpreter) unaryOverloads(m model.IUnaryExpression) ([]convert.Overlo
 				Result:   evalLn,
 			},
 		}, nil
+	case *model.Precision:
+		return []convert.Overload[evalUnarySignature]{
+			{
+				Operands: []types.IType{types.Date},
+				Result:   evalPrecisionDateTime,
+			},
+			{
+				Operands: []types.IType{types.DateTime},
+				Result:   evalPrecisionDateTime,
+			},
+			{
+				Operands: []types.IType{types.Time},
+				Result:   evalPrecisionTime,
+			},
+		}, nil
 	case *model.Exists:
 		return []convert.Overload[evalUnarySignature]{
 			{

model/model.go

@@ -663,6 +663,9 @@ type Floor struct{ *UnaryExpression }
 // Ln  is https://cql.hl7.org/04-logicalspecification.html#ln.
 type Ln struct{ *UnaryExpression }
 
+// Precision  is https://cql.hl7.org/04-logicalspecification.html#precision.
+type Precision struct{ *UnaryExpression }
+
 // SingletonFrom is https://cql.hl7.org/04-logicalspecification.html#singletonfrom.
 type SingletonFrom struct{ *UnaryExpression }
 
@@ -1140,6 +1143,9 @@ func (a *Floor) GetName() string { return "Floor" }
 // GetName returns the name of the system operator.
 func (a *Ln) GetName() string { return "Ln" }
 
+// GetName returns the name of the system operator.
+func (a *Precision) GetName() string { return "Precision" }
+
 // GetName returns the name of the system operator.
 func (a *As) GetName() string { return "As" }
 

parser/operators.go

@@ -700,6 +700,21 @@ func (p *Parser) loadSystemOperators() error {
 			operands: [][]types.IType{{types.Quantity}},
 			model:    negateModel(types.Quantity),
 		},
+		{
+			name:     "Precision",
+			operands: [][]types.IType{{types.Date}},
+			model:    precisionModel(),
+		},
+		{
+			name:     "Precision",
+			operands: [][]types.IType{{types.DateTime}},
+			model:    precisionModel(),
+		},
+		{
+			name:     "Precision",
+			operands: [][]types.IType{{types.Time}},
+			model:    precisionModel(),
+		},
 		{
 			name:     "Subtract",
 			operands: [][]types.IType{{types.Integer, types.Integer}},
@@ -2142,6 +2157,16 @@ func powerModel(resultType types.System) func() model.IExpression {
 	}
 }
 
+func precisionModel() func() model.IExpression {
+	return func() model.IExpression {
+		return &model.Precision{
+			UnaryExpression: &model.UnaryExpression{
+				Expression: model.ResultType(types.Integer),
+			},
+		}
+	}
+}
+
 func (v *visitor) parseCoalesce(m *model.Coalesce, operands []model.IExpression) (model.IExpression, error) {
 	if len(operands) == 1 {
 		// This is the list overload.

parser/operators_test.go

@@ -515,6 +515,16 @@ func TestBuiltInFunctions(t *testing.T) {
 				},
 			},
 		},
+		{
+			name: "Arithmetic Precision",
+			cql:  "Precision(@2014)",
+			want: &model.Precision{
+				UnaryExpression: &model.UnaryExpression{
+					Operand:    model.NewLiteral("@2014", types.Date),
+					Expression: model.ResultType(types.Integer),
+				},
+			},
+		},
 		{
 			name: "Arithmetic Addition",
 			cql:  "Add(1, 2)",

tests/enginetests/operator_arithmetic_test.go

@@ -422,6 +422,104 @@ func TestLn(t *testing.T) {
 	}
 }
 
+func TestPrecision(t *testing.T) {
+	tests := []struct {
+		name       string
+		cql        string
+		wantModel  model.IExpression
+		wantResult result.Value
+	}{
+		{
+			name: "Decimal",
+			cql:  "Precision(@2014)",
+			wantModel: &model.Precision{
+				UnaryExpression: &model.UnaryExpression{
+					Operand:    model.NewLiteral("@2014", types.Date),
+					Expression: model.ResultType(types.Integer),
+				},
+			},
+			wantResult: newOrFatal(t, 4),
+		},
+		{
+			name:       "Date Year",
+			cql:        "Precision(@2014)",
+			wantResult: newOrFatal(t, 4),
+		},
+		{
+			name:       "Date Month",
+			cql:        "Precision(@2014-02)",
+			wantResult: newOrFatal(t, 6),
+		},
+		{
+			name:       "Date Day",
+			cql:        "Precision(@2014-01-01)",
+			wantResult: newOrFatal(t, 8),
+		},
+		{
+			name:       "DateTime Hour",
+			cql:        "Precision(@2014-01-01T10)",
+			wantResult: newOrFatal(t, 10),
+		},
+		{
+			name:       "DateTime Minute",
+			cql:        "Precision(@2014-01-01T10:10)",
+			wantResult: newOrFatal(t, 12),
+		},
+		{
+			name:       "DateTime Second",
+			cql:        "Precision(@2014-01-01T10:10:30)",
+			wantResult: newOrFatal(t, 14),
+		},
+		{
+			name:       "DateTime Millisecond",
+			cql:        "Precision(@2014-01-01T10:10:30.000Z)",
+			wantResult: newOrFatal(t, 17),
+		},
+		{
+			name:       "Time Hour",
+			cql:        "Precision(@T10)",
+			wantResult: newOrFatal(t, 2),
+		},
+		{
+			name:       "Time Millisecond",
+			cql:        "Precision(@T01:01:00.000)",
+			wantResult: newOrFatal(t, 9),
+		},
+		{
+			name:       "Time Millisecond",
+			cql:        "Precision(@2014-01-02T01:01:00.000Z)",
+			wantResult: newOrFatal(t, 17),
+		},
+		{
+			name:       "Null",
+			cql:        "Precision(null as Date)",
+			wantResult: newOrFatal(t, nil),
+		},
+	}
+
+	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 TestAdd(t *testing.T) {
 	tests := []struct {
 		name       string

tests/spectests/exclusions/exclusions.go

@@ -55,7 +55,6 @@ func XMLTestFileExclusionDefinitions() map[string]XMLTestFileExclusions {
 				"HighBoundary",
 				"Log",
 				"LowBoundary",
-				"Precision",
 				"Round",
 			},
 			NamesExcludes: []string{
@@ -71,6 +70,7 @@ func XMLTestFileExclusionDefinitions() map[string]XMLTestFileExclusions {
 				// TODO: b/342061783 - Got unexpected result.
 				"Subtract2And11D",
 				"TruncatedDivide10d1ByNeg3D1Quantity",
+				"PrecisionDecimal", // Does not yet support trailing zeros.
 				// TODO: b/344002938 - xml test is wrong, asserts with a time zone.
 				"DateTimeMinValue",
 				"DateTimeMaxValue",