version 0.6.0

* Check for zero step value to void infinite loops
* Add `new()` fn for creating ranges with checks
* Add `to_array()` method
* Add `is_empty()` method
* Add more tests

ranges.v

@@ -7,14 +7,17 @@ struct Range[T] {
 	start  T
 	end    T
 	step   T
-	is_neg bool
+	is_rev bool // Is set to true if range end value is lesser than start value.
 mut:
 	cur T
 }
 
 // next returns the new element from range or none if range end is reached.
 pub fn (mut r Range[T]) next() ?T {
-	if (r.is_neg && r.cur < r.end) || (!r.is_neg && r.cur > r.end) {
+	if r.step == $zero(T) {
+		return none
+	}
+	if (r.is_rev && r.cur < r.end) || (!r.is_rev && r.cur > r.end) {
 		return none
 	}
 	defer {
@@ -29,6 +32,11 @@ pub fn (mut r Range[T]) reset() {
 	r.cur = r.start
 }
 
+// bounds returns the start, end and step values of range.
+pub fn (r Range[T]) bounds() (T, T, T) {
+	return r.start, r.end, r.step
+}
+
 // with_step returns copy of the range with new step value.
 pub fn (r Range[T]) with_step[T](step T) Range[T] {
 	return Range[T]{
@@ -38,6 +46,33 @@ pub fn (r Range[T]) with_step[T](step T) Range[T] {
 	}
 }
 
+// to_array returns an array of elements from the range.
+pub fn (r Range[T]) to_array() []T {
+	if r.is_empty() {
+		return []T{}
+	}
+
+	mut cap := 0
+
+	$if T is $int || T is $float {
+		cap = int((r.end - r.start) / r.step + T(1))
+	} $else $if T is big.Integer {
+		cap = ((r.end - r.start) / r.step + big.one_int).int()
+	}
+
+	mut arr := []T{cap: cap}
+	for el in r {
+		arr << el
+	}
+	return arr
+}
+
+// is_empty reports is the range instance empty (has no values).
+pub fn (r Range[T]) is_empty() bool {
+	empty := $zero(Range[T])
+	return r == empty
+}
+
 // range creates new Range iterator with given start, end and step values.
 //
 // Generally numbers are expected. If type is a struct the following operators
@@ -46,14 +81,34 @@ pub fn (r Range[T]) with_step[T](step T) Range[T] {
 //
 // The range includes the end value.
 //
-// Note: Zero step value will cause an infitite loop!
+// Note: If range cannot be created the empty range will be returned. See also `new()`.
 pub fn range[T](start T, end T, step T) Range[T] {
+	return new(start, end, step) or { Range[T]{} }
+}
+
+// new creates new range with given start, end and step values.
+// Unlike `range`, this function will return an error if:
+//
+// * step value is zero;
+// * step > 0, but start value is greather than end value;
+// * step < 0, but start value is lesser than end value.
+pub fn new[T](start T, end T, step T) !Range[T] {
+	zero := $zero(T)
+	if step == zero {
+		return error('step value is zero')
+	}
+	if step > zero && start > end {
+		return error('step is positive, but start value is greather than end value')
+	}
+	if step < zero && start <= end {
+		return error('step is negative, but start value is lesser than or equals end value')
+	}
 	return Range[T]{
 		start:  start
 		end:    end
 		step:   step
 		cur:    start
-		is_neg: start > end
+		is_rev: start > end
 	}
 }
 
@@ -69,28 +124,28 @@ pub:
 // Use from_string_custom if you want to use custom type with special string
 // convertion rules.
 //
-// Supported string formats are `start-end` and `start[:step]end`. start and end
+// Supported string formats are `start-end[/step]` and `start[:step]:end`. start
-// values are sepatared by 'sep' which is hypen (`-`) by default. Single number
+// and end values are sepatared by 'sep' which is hypen (`-`) by default. Single
-// will be interpreted as range of one element. Several ranges can be specified
+// number will be interpreted as range of one element. Several ranges can be
-// in a line, separated by 'group_sep' (comma by default). 'sep' and 'group_sep'
+// specified in a line, separated by 'group_sep' (comma by default). 'sep' and
-// can be overrided by user.
+// 'group_sep' can be overrided by user.
 //
 // Some example input strings:
 //
 // * `5` - range from 5 to 5 (single element).
 // * `0-10` - range from 0 to 10.
+// * `0-100/5` - range in Cron-style syntax from 0 to 100 with step 5.
 // * `15:-1:0` - range in MathLab-style syntax from 15 to 0 with negative step -1.
 // * `1..8` - range from 1 to 8 with '..' sep.
 // * `0-7,64-71` - multiple ranges: from 0 to 7 and from 64 to 71.
 //
-// Only MathLab-style syntax allows you to specify a step directly in the string.
+// If the step value is not specified, it will be set to one.
-// For all other cases, the step is equal to one.
 //
 // Example: assert ranges.from_string[int]('1-7')! == [ranges.range(1, 7, 1)]
 pub fn from_string[T](s string, config RangeFromStringConfig) ![]Range[T] {
 	mut result := []Range[T]{}
 	for i in s.split(config.group_sep) {
-		range_str := parse_string(i, config.sep)!
+		range_str := split_string(i, config.sep)!
 		// vfmt off
 		result << range[T](
 			convert_string[T](range_str[0])!,
@@ -133,7 +188,7 @@ pub type StringConvertFn[T] = fn (s string) !T
 pub fn from_string_custom[T](s string, conv StringConvertFn[T], config RangeFromStringConfig) ![]Range[T] {
 	mut result := []Range[T]{}
 	for i in s.split(config.group_sep) {
-		range_str := parse_string(i, config.sep)!
+		range_str := split_string(i, config.sep)!
 		start := conv[T](range_str[0])!
 		end := conv[T](range_str[1])!
 		step := conv[T](range_str[2])!
@@ -142,7 +197,7 @@ pub fn from_string_custom[T](s string, conv StringConvertFn[T], config RangeFrom
 	return result
 }
 
-fn parse_string(s string, sep string) ![]string {
+fn split_string(s string, sep string) ![]string {
 	parts := s.split(sep)
 	if parts.any(|x| x.is_blank()) || parts.len !in [1, 2, 3] {
 		return error('`start${sep}end` or `start[:step]:end`' +
@@ -150,12 +205,19 @@ fn parse_string(s string, sep string) ![]string {
 	}
 	if parts.len == 1 {
 		return [parts[0], parts[0], '1']
-	} else if parts.len == 2 {
+	}
+	if parts.len == 2 {
+		if parts[1].contains('/') {
+			end, step := parts[1].split_once('/') or { '', '' }
+			return [parts[0], end, step]
+		}
 		return [parts[0], parts[1], '1']
-	} else if sep == ':' && parts.len == 3 {
+	}
+	if sep == ':' && parts.len == 3 {
 		return [parts[0], parts[2], parts[1]]
 	}
-	return error('invalid range string: ${s}')
+	return error('invalid range string: expected `start[${sep}step]${sep}end` ' +
+		'or `start${sep}end[/step]` format, got `${s}`')
 }
 
 fn convert_string[T](s string) !T {

ranges_test.v

@@ -69,10 +69,15 @@ fn test_range_bigint() {
 
 fn test_range_from_string() {
 	assert ranges.from_string[int]('0-10')! == [ranges.range(0, 10, 1)]
-	assert ranges.from_string[int]('0-7,8-15')! == [ranges.range(0, 7, 1),
+	assert ranges.from_string[int]('0-7,8-15')! == [
-		ranges.range(8, 15, 1)]
+		ranges.range(0, 7, 1),
-	assert ranges.from_string[int]('0-6,7,8-15')! == [ranges.range(0, 6, 1),
+		ranges.range(8, 15, 1),
-		ranges.range(7, 7, 1), ranges.range(8, 15, 1)]
+	]
+	assert ranges.from_string[int]('0-6,7,8-15')! == [
+		ranges.range(0, 6, 1),
+		ranges.range(7, 7, 1),
+		ranges.range(8, 15, 1),
+	]
 	assert ranges.from_string[i64]('5:2:15', sep: ':')! == [ranges.range[i64](5, 15, 2)]
 	assert ranges.from_string[int]('100:-1:0', sep: ':')! == [
 		ranges.range(100, 0, -1),
@@ -87,6 +92,7 @@ fn test_range_from_string() {
 	assert ranges.from_string[f32]('0.0..99.99', sep: '..')! == [
 		ranges.range[f32](0.0, 99.99, 1),
 	]
+	assert ranges.from_string[int]('0-100/5')! == [ranges.range(0, 100, 5)]
 }
 
 struct Int {
@@ -110,23 +116,29 @@ fn (a Int) == (b Int) bool {
 }
 
 fn test_range_custom_type() {
-	// vfmt off
 	mut result := []Int{}
-	for i in ranges.range[Int](Int{ val: 0 }, Int{ val: 5 }, Int{ val: 1 }) {
+	start := Int{0}
+	end := Int{5}
+	step := Int{1}
+	for i in ranges.range[Int](start, end, step) {
 		result << i
 	}
-	assert result == [Int{0}, Int{1}, Int{2}, Int{3}, Int{4}, Int{5}]
+	assert result == [
-	// vfmt on
+		Int{0},
+		Int{1},
+		Int{2},
+		Int{3},
+		Int{4},
+		Int{5},
+	]
 }
 
-//
-// Note this bug: https://github.com/vlang/v/issues/26156
-//
-
 fn test_range_from_string_custom_type() {
 	assert ranges.from_string_custom[Int]('0-5', fn (s string) !Int {
 		if s.is_int() {
-			return Int{ val: s.int() }
+			return Int{
+				val: s.int()
+			}
 		} else {
 			return error('invalid integer value: ${s}')
 		}
@@ -178,3 +190,119 @@ fn test_range_new_with_step() {
 	}
 	assert result == [0, 2, 4]
 }
+
+fn test_range_bounds() {
+	r := ranges.range(0, 10, 2)
+	a, b, c := r.bounds()
+	assert a == 0
+	assert b == 10
+	assert c == 2
+}
+
+fn test_range_to_array_int() {
+	r := ranges.range(0, 5, 1)
+	assert r.to_array() == [0, 1, 2, 3, 4, 5]
+}
+
+fn test_range_to_array_float() {
+	r := ranges.range[f64](3.0, 3.14, 0.01)
+	assert r.to_array() == [
+		f64(3.0),
+		3.01,
+		3.0199999999999996,
+		3.0299999999999994,
+		3.039999999999999,
+		3.049999999999999,
+		3.0599999999999987,
+		3.0699999999999985,
+		3.0799999999999983,
+		3.089999999999998,
+		3.099999999999998,
+		3.1099999999999977,
+		3.1199999999999974,
+		3.1299999999999972,
+		3.139999999999997,
+	]
+}
+
+fn test_range_to_array_bigint() {
+	r := ranges.range(big.zero_int, big.three_int, big.one_int)
+	assert r.to_array() == [big.zero_int, big.one_int, big.two_int, big.three_int]
+}
+
+fn test_range_empty() {
+	r := ranges.range(0, 0, 0)
+	assert r.to_array() == []
+}
+
+fn test_range_empty_bigint() {
+	r := ranges.range(big.zero_int, big.zero_int, big.zero_int)
+	assert r.to_array() == []
+}
+
+fn test_range_is_empty() {
+	r := ranges.range(0, 0, -9000)
+	assert r.is_empty()
+	assert r.to_array() == []
+}
+
+fn test_new() {
+	r := ranges.new(0, 10, 1)!
+	a, b, c := r.bounds()
+	assert a == 0
+	assert b == 10
+	assert c == 1
+	assert r.to_array() == [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+}
+
+fn test_new_with_step() {
+	r := ranges.new(0, 10, 2)!
+	assert r.to_array() == [0, 2, 4, 6, 8, 10]
+}
+
+fn test_new_reversed() {
+	r := ranges.new(10, 0, -1)!
+	assert r.to_array() == [10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
+}
+
+fn test_new_with_negative_step() {
+	r := ranges.new(10, 0, -2)!
+	assert r.to_array() == [10, 8, 6, 4, 2, 0]
+}
+
+fn test_new_single_item() {
+	r := ranges.new(5, 5, 1)!
+	assert r.to_array() == [5]
+}
+
+fn test_new_error_zero_step() {
+	if _ := ranges.new(0, 10, 0) {
+		assert false, 'expected error for zero step'
+	} else {
+		assert err.msg() == 'step value is zero'
+	}
+}
+
+fn test_new_error_positive_step_start_gt_end() {
+	if _ := ranges.new(10, 0, 1) {
+		assert false, 'expected error for positive step with start > end'
+	} else {
+		assert err.msg() == 'step is positive, but start value is greather than end value'
+	}
+}
+
+fn test_new_error_negative_step_start_lt_end() {
+	if _ := ranges.new(0, 10, -1) {
+		assert false, 'expected error for negative step with start <= end'
+	} else {
+		assert err.msg() == 'step is negative, but start value is lesser than or equals end value'
+	}
+}
+
+fn test_new_error_negative_step_start_eq_end() {
+	if _ := ranges.new(5, 5, -1) {
+		assert false, 'expected error for negative step with start <= end'
+	} else {
+		assert err.msg() == 'step is negative, but start value is lesser than or equals end value'
+	}
+}

v.mod

@@ -1,7 +1,7 @@
 Module {
 	name: 'ranges'
 	description: 'Operating with ranges of numbers'
-	version: '0.3.0'
+	version: '0.6.0'
 	license: 'Unlicense'
 	dependencies: []
 }