diff --git a/vlib/builtin/js/byte.js.v b/vlib/builtin/js/byte.js.v
index 5dfcc50f9c..9ba4e6cf05 100644
--- a/vlib/builtin/js/byte.js.v
+++ b/vlib/builtin/js/byte.js.v
@@ -39,7 +39,7 @@ pub fn (c u8) is_digit() bool {
 // Example: assert u8(`F`) == true
 @[inline]
 pub fn (c u8) is_hex_digit() bool {
-	return (c >= `0` && c <= `9`) || (c >= `a` && c <= `f`) || (c >= `A` && c <= `F`)
+	return c.is_digit() || (c >= `a` && c <= `f`) || (c >= `A` && c <= `F`)
 }
 
 // is_oct_digit returns `true` if the byte is in range 0-7 and `false` otherwise.
diff --git a/vlib/builtin/js/string.js.v b/vlib/builtin/js/string.js.v
index e6d09a5565..983361bb09 100644
--- a/vlib/builtin/js/string.js.v
+++ b/vlib/builtin/js/string.js.v
@@ -952,7 +952,7 @@ pub fn (s string) is_capital() bool {
 // Example: assert 'Hello. World.'.starts_with_capital() == true
 @[direct_array_access]
 pub fn (s string) starts_with_capital() bool {
-	if s.len == 0 || !(s[0] >= `A` && s[0] <= `Z`) {
+	if s.len == 0 || !s[0].is_capital() {
 		return false
 	}
 	return true
diff --git a/vlib/builtin/string.v b/vlib/builtin/string.v
index 4dcb9f6ac9..6cf1b50e1f 100644
--- a/vlib/builtin/string.v
+++ b/vlib/builtin/string.v
@@ -1518,7 +1518,7 @@ pub fn (s string) to_lower() string {
 	unsafe {
 		mut b := malloc_noscan(s.len + 1)
 		for i in 0 .. s.len {
-			if s.str[i] >= `A` && s.str[i] <= `Z` {
+			if s.str[i].is_capital() {
 				b[i] = s.str[i] + 32
 			} else {
 				b[i] = s.str[i]
@@ -1637,7 +1637,7 @@ pub fn (s string) is_capital() bool {
 // Example: assert 'Hello. World.'.starts_with_capital() == true
 @[direct_array_access]
 pub fn (s string) starts_with_capital() bool {
-	if s.len == 0 || !(s[0] >= `A` && s[0] <= `Z`) {
+	if s.len == 0 || !s[0].is_capital() {
 		return false
 	}
 	return true
@@ -2043,7 +2043,7 @@ pub fn (c u8) is_digit() bool {
 // Example: assert u8(`F`).is_hex_digit() == true
 @[inline]
 pub fn (c u8) is_hex_digit() bool {
-	return (c >= `0` && c <= `9`) || (c >= `a` && c <= `f`) || (c >= `A` && c <= `F`)
+	return c.is_digit() || (c >= `a` && c <= `f`) || (c >= `A` && c <= `F`)
 }
 
 // is_oct_digit returns `true` if the byte is in range 0-7 and `false` otherwise.
@@ -2652,9 +2652,9 @@ pub fn (s string) camel_to_snake() string {
 	}
 	mut b := unsafe { malloc_noscan(2 * s.len + 1) }
 	mut prev_is_upper := false
-	first_char, second_char := if s[0] >= `A` && s[0] <= `Z` {
-		lower_first_c := if s[0] >= `A` && s[0] <= `Z` { s[0] + 32 } else { s[0] }
-		lower_second_c := if s[1] >= `A` && s[1] <= `Z` {
+	first_char, second_char := if s[0].is_capital() {
+		lower_first_c := s[0] + 32
+		lower_second_c := if s[1].is_capital() {
 			prev_is_upper = true
 			s[1] + 32
 		} else {
@@ -2663,7 +2663,7 @@ pub fn (s string) camel_to_snake() string {
 		lower_first_c, lower_second_c
 	} else {
 		lower_first_c := s[0]
-		second_c := if s[1] >= `A` && s[1] <= `Z` { u8(`_`) } else { s[1] }
+		second_c := if s[1].is_capital() { u8(`_`) } else { s[1] }
 		lower_first_c, second_c
 	}
 	unsafe {
@@ -2676,7 +2676,7 @@ pub fn (s string) camel_to_snake() string {
 	mut c_is_upper := false
 	for i in pos .. s.len {
 		c := s[i]
-		c_is_upper = c >= `A` && c <= `Z`
+		c_is_upper = c.is_capital()
 		lower_c = if c_is_upper { c + 32 } else { c }
 		if !prev_is_upper && c_is_upper {
 			// aB => a_b, if prev has `_`, then do not add `_`
diff --git a/vlib/net/http/cookie.v b/vlib/net/http/cookie.v
index ef49a251c2..ed4328ef04 100644
--- a/vlib/net/http/cookie.v
+++ b/vlib/net/http/cookie.v
@@ -248,7 +248,7 @@ pub fn is_cookie_domain_name(_s string) bool {
 	mut part_len := 0
 	for i, _ in s {
 		c := s[i]
-		if (`a` <= c && c <= `z`) || (`A` <= c && c <= `Z`) {
+		if c.is_letter() {
 			// No '_' allowed here (in contrast to package net).
 			ok = true
 			part_len++
diff --git a/vlib/net/urllib/urllib.v b/vlib/net/urllib/urllib.v
index 94927d9024..4ed8bb6b25 100644
--- a/vlib/net/urllib/urllib.v
+++ b/vlib/net/urllib/urllib.v
@@ -38,7 +38,7 @@ fn error_msg(message string, val string) string {
 // reserved characters correctly. See golang.org/issue/5684.
 fn should_escape(c u8, mode EncodingMode) bool {
 	// §2.3 Unreserved characters (alphanum)
-	if (`a` <= c && c <= `z`) || (`A` <= c && c <= `Z`) || (`0` <= c && c <= `9`) {
+	if c.is_alnum() {
 		return false
 	}
 	if mode == .encode_host || mode == .encode_zone {
@@ -388,9 +388,9 @@ fn (u &Userinfo) str() string {
 fn split_by_scheme(rawurl string) ![]string {
 	for i in 0 .. rawurl.len {
 		c := rawurl[i]
-		if (`a` <= c && c <= `z`) || (`A` <= c && c <= `Z`) {
+		if c.is_letter() {
 			// do nothing
-		} else if (`0` <= c && c <= `9`) || (c == `+` || c == `-` || c == `.`) {
+		} else if c.is_digit() || c in [`+`, `-`, `.`] {
 			if i == 0 {
 				return ['', rawurl]
 			}
@@ -1016,13 +1016,7 @@ pub fn split_host_port(hostport string) (string, string) {
 // It doesn't validate pct-encoded. The caller does that via fn unescape.
 pub fn valid_userinfo(s string) bool {
 	for r in s {
-		if `A` <= r && r <= `Z` {
-			continue
-		}
-		if `a` <= r && r <= `z` {
-			continue
-		}
-		if `0` <= r && r <= `9` {
+		if r.is_alnum() {
 			continue
 		}
 		match r {
diff --git a/vlib/strings/strings.v b/vlib/strings/strings.v
index df08a26dbe..4f18e22fa8 100644
--- a/vlib/strings/strings.v
+++ b/vlib/strings/strings.v
@@ -134,7 +134,7 @@ pub fn split_capital(s string) []string {
 	mut res := []string{}
 	mut word_start := 0
 	for idx, c in s {
-		if c >= `A` && c <= `Z` {
+		if c.is_capital() {
 			if word_start != idx {
 				res << s#[word_start..idx]
 			}
diff --git a/vlib/toml/util/util.v b/vlib/toml/util/util.v
index a4a9e24d4d..479c84b159 100644
--- a/vlib/toml/util/util.v
+++ b/vlib/toml/util/util.v
@@ -6,7 +6,7 @@ module util
 // is_key_char returns true if the given u8 is a valid key character.
 @[inline]
 pub fn is_key_char(c u8) bool {
-	return (c >= `a` && c <= `z`) || (c >= `A` && c <= `Z`) // || c == `_`  || c == `-` <- these are identified when tokenizing
+	return c.is_letter() // || c == `_`  || c == `-` <- these are identified when tokenizing
 }
 
 // is_ascii_control_character returns true if `byte_char` is an ASCII control character.
diff --git a/vlib/v/scanner/scanner.v b/vlib/v/scanner/scanner.v
index ec0f2eda2f..ec56a76e7b 100644
--- a/vlib/v/scanner/scanner.v
+++ b/vlib/v/scanner/scanner.v
@@ -239,7 +239,7 @@ fn (mut s Scanner) ident_name() string {
 	s.pos++
 	for s.pos < s.text.len {
 		c := s.text[s.pos]
-		if (c >= `a` && c <= `z`) || (c >= `A` && c <= `Z`) || (c >= `0` && c <= `9`) || c == `_` {
+		if c.is_alnum() || c == `_` {
 			s.pos++
 			continue
 		}
diff --git a/vlib/v/util/scanning.v b/vlib/v/util/scanning.v
index cb312d8f3c..e6eeac7c68 100644
--- a/vlib/v/util/scanning.v
+++ b/vlib/v/util/scanning.v
@@ -2,17 +2,17 @@ module util
 
 @[inline]
 pub fn is_name_char(c u8) bool {
-	return (c >= `a` && c <= `z`) || (c >= `A` && c <= `Z`) || c == `_`
+	return c.is_letter() || c == `_`
 }
 
 @[inline]
 pub fn is_func_char(c u8) bool {
-	return (c >= `a` && c <= `z`) || (c >= `A` && c <= `Z`) || c == `_` || (c >= `0` && c <= `9`)
+	return c.is_letter() || c == `_` || c.is_digit()
 }
 
 pub fn contains_capital(s string) bool {
 	for c in s {
-		if c >= `A` && c <= `Z` {
+		if c.is_capital() {
 			return true
 		}
 	}
diff --git a/vlib/v2/scanner/scanner.v b/vlib/v2/scanner/scanner.v
index 9177b9a502..bd20b22c8e 100644
--- a/vlib/v2/scanner/scanner.v
+++ b/vlib/v2/scanner/scanner.v
@@ -131,8 +131,7 @@ pub fn (mut s Scanner) scan() token.Token {
 		}
 		for s.offset < s.src.len {
 			c3 := s.src[s.offset]
-			if (c3 >= `a` && c3 <= `z`) || (c3 >= `A` && c3 <= `Z`)
-				|| (c3 >= `0` && c3 <= `9`) || c3 == `_` {
+			if c3.is_alnum() || c3 == `_` {
 				s.offset++
 				continue
 			}