Add ceil(), floor() and round() function

Fixes #476

Author: antonmedv

Diff for: builtin/builtin.go

@@ -126,6 +126,48 @@ var Builtins = []*ast.Function{
 			return anyType, fmt.Errorf("invalid argument for abs (type %s)", args[0])
 		},
 	},
+	{
+		Name: "ceil",
+		Fast: Ceil,
+		Validate: func(args []reflect.Type) (reflect.Type, error) {
+			if len(args) != 1 {
+				return anyType, fmt.Errorf("invalid number of arguments (expected 1, got %d)", len(args))
+			}
+			switch kind(args[0]) {
+			case reflect.Float32, reflect.Float64, reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Interface:
+				return floatType, nil
+			}
+			return anyType, fmt.Errorf("invalid argument for ceil (type %s)", args[0])
+		},
+	},
+	{
+		Name: "floor",
+		Fast: Floor,
+		Validate: func(args []reflect.Type) (reflect.Type, error) {
+			if len(args) != 1 {
+				return anyType, fmt.Errorf("invalid number of arguments (expected 1, got %d)", len(args))
+			}
+			switch kind(args[0]) {
+			case reflect.Float32, reflect.Float64, reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Interface:
+				return floatType, nil
+			}
+			return anyType, fmt.Errorf("invalid argument for floor (type %s)", args[0])
+		},
+	},
+	{
+		Name: "round",
+		Fast: Round,
+		Validate: func(args []reflect.Type) (reflect.Type, error) {
+			if len(args) != 1 {
+				return anyType, fmt.Errorf("invalid number of arguments (expected 1, got %d)", len(args))
+			}
+			switch kind(args[0]) {
+			case reflect.Float32, reflect.Float64, reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64, reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Interface:
+				return floatType, nil
+			}
+			return anyType, fmt.Errorf("invalid argument for floor (type %s)", args[0])
+		},
+	},
 	{
 		Name: "int",
 		Fast: Int,

Diff for: builtin/builtin_test.go

@@ -36,6 +36,13 @@ func TestBuiltin(t *testing.T) {
 		{`abs(-5)`, 5},
 		{`abs(.5)`, .5},
 		{`abs(-.5)`, .5},
+		{`ceil(5.5)`, 6.0},
+		{`ceil(5)`, 5.0},
+		{`floor(5.5)`, 5.0},
+		{`floor(5)`, 5.0},
+		{`round(5.5)`, 6.0},
+		{`round(5)`, 5.0},
+		{`round(5.49)`, 5.0},
 		{`int(5.5)`, 5},
 		{`int(5)`, 5},
 		{`int("5")`, 5},

Diff for: builtin/func.go

@@ -2,6 +2,7 @@ package builtin
 
 import (
 	"fmt"
+	"math"
 	"reflect"
 	"strconv"
 
@@ -138,6 +139,42 @@ func Abs(x any) any {
 	panic(fmt.Sprintf("invalid argument for abs (type %T)", x))
 }
 
+func Ceil(x any) any {
+	switch x := x.(type) {
+	case float32:
+		return math.Ceil(float64(x))
+	case float64:
+		return math.Ceil(x)
+	case int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64:
+		return Float(x)
+	}
+	panic(fmt.Sprintf("invalid argument for ceil (type %T)", x))
+}
+
+func Floor(x any) any {
+	switch x := x.(type) {
+	case float32:
+		return math.Floor(float64(x))
+	case float64:
+		return math.Floor(x)
+	case int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64:
+		return Float(x)
+	}
+	panic(fmt.Sprintf("invalid argument for floor (type %T)", x))
+}
+
+func Round(x any) any {
+	switch x := x.(type) {
+	case float32:
+		return math.Round(float64(x))
+	case float64:
+		return math.Round(x)
+	case int, int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64:
+		return Float(x)
+	}
+	panic(fmt.Sprintf("invalid argument for round (type %T)", x))
+}
+
 func Int(x any) any {
 	switch x := x.(type) {
 	case float32:

Diff for: docs/Language-Definition.md

@@ -380,6 +380,30 @@ min(5, 7) == 5
 
 Returns the absolute value of a number.
 
+### ceil(n)
+
+Returns the least integer value greater than or equal to x.
+
+```expr
+ceil(1.5) == 2.0
+```
+
+### floor(n)
+
+Returns the greatest integer value less than or equal to x.
+
+```expr
+floor(1.5) == 1.0
+```
+
+### round(n)
+
+Returns the nearest integer, rounding half away from zero.
+
+```expr
+round(1.5) == 2.0
+```
+
 ## Array Functions
 
 ### all(array, predicate)