all: new string interpolation in pure V (#10181)

vlib/strconv/utilities.v

@@ -81,7 +81,9 @@ fn get_string_special(neg bool, expZero bool, mantZero bool) string {
  32 bit functions
 
 */
-fn decimal_len_32(u u32) int {
+// decimal_len_32 return the number of decimal digits of the input
+[deprecated]
+pub fn decimal_len_32(u u32) int {
 	// Function precondition: u is not a 10-digit number.
 	// (9 digits are sufficient for round-tripping.)
 	// This benchmarked faster than the log2 approach used for u64.
@@ -172,7 +174,9 @@ fn pow5_bits(e int) int {
  64 bit functions
 
 */
-fn decimal_len_64(u u64) int {
+[deprecated]
+// decimal_len_64 return the number of decimal digits of the input
+pub fn decimal_len_64(u u64) int {
 	// http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
 	log2 := 64 - bits.leading_zeros_64(u) - 1
 	t := (log2 + 1) * 1233 >> 12
@@ -227,15 +231,44 @@ f64 to string with string format
 
 */
 
+// TODO: Investigate precision issues
 // f32_to_str_l return a string with the f32 converted in a string in decimal notation
-pub fn f32_to_str_l(f f64) string {
-	return f64_to_str_l(f32(f))
+[manualfree]
+pub fn f32_to_str_l(f f32) string {
+	s := f32_to_str(f,6)
+	res := fxx_to_str_l_parse(s)
+	unsafe{s.free()}
+	return res
 }
 
-// f64_to_str_l return a string with the f64 converted in a string in decimal notation
+[manualfree]
+pub fn f32_to_str_l_no_dot(f f32) string {
+	s := f32_to_str(f,6)
+	res := fxx_to_str_l_parse_no_dot(s)
+	unsafe{s.free()}
+	return res
+}
+
+[manualfree]
 pub fn f64_to_str_l(f f64) string {
 	s := f64_to_str(f,18)
+	res := fxx_to_str_l_parse(s)
+	unsafe{s.free()}
+	return res
+}
 
+[manualfree]
+pub fn f64_to_str_l_no_dot(f f64) string {
+	s := f64_to_str(f,18)
+	res := fxx_to_str_l_parse_no_dot(s)
+	unsafe{s.free()}
+	return res
+}
+
+
+// f64_to_str_l return a string with the f64 converted in a string in decimal notation
+[manualfree]
+pub fn fxx_to_str_l_parse(s string) string {
 	// check for +inf -inf Nan
 	if s.len > 2 && (s[0] == `n` || s[1] == `i`) {
 		return s
@@ -287,8 +320,11 @@ pub fn f64_to_str_l(f f64) string {
 		exp_sgn = 1
 		i++
 	}
-	for c in s[i..] {
-		exp = exp * 10 + int(c-`0`)
+
+	mut c := i
+	for c < s.len {
+		exp = exp * 10 + int(s[c]-`0`)
+		c++
 	}
 
 	// allocate exp+32 chars for the return string
@@ -296,7 +332,7 @@ pub fn f64_to_str_l(f f64) string {
 	mut r_i := 0  // result string buffer index
 
 	//println("s:${sgn} b:${b[0]} es:${exp_sgn} exp:${exp}")
-
+	
 	if sgn == 1 {
 		if m_sgn_flag {
 			res[r_i] = `+`
@@ -344,6 +380,136 @@ pub fn f64_to_str_l(f f64) string {
 			i++
 		}
 	}
+/*
+	// remove the dot form the numbers like 2.
+	if r_i > 1 && res[r_i-1] == `.` {
+		r_i--
+	}
+*/	
+	res[r_i] = 0
+	return unsafe { tos(res.data,r_i) }
+}
+
+// f64_to_str_l return a string with the f64 converted in a string in decimal notation
+[manualfree]
+pub fn fxx_to_str_l_parse_no_dot(s string) string {
+	// check for +inf -inf Nan
+	if s.len > 2 && (s[0] == `n` || s[1] == `i`) {
+		return s
+	}
+
+	m_sgn_flag := false
+	mut sgn        := 1
+	mut b          := [26]byte{}
+	mut d_pos      := 1
+	mut i          := 0
+	mut i1         := 0
+	mut exp        := 0
+	mut exp_sgn    := 1
+
+	// get sign and decimal parts
+	for c in s {
+		if c == `-` {
+			sgn = -1
+			i++
+		} else if c == `+` {
+			sgn = 1
+			i++
+		}
+		else if c >= `0` && c <= `9` {
+			b[i1] = c
+			i1++
+			i++
+		} else if c == `.` {
+			if sgn > 0 {
+				d_pos = i
+			} else {
+				d_pos = i-1
+			}
+			i++
+		} else if c == `e` {
+			i++
+			break
+		} else {
+			return "Float conversion error!!"
+		}
+	}
+	b[i1] = 0
+
+	// get exponent
+	if s[i] == `-` {
+		exp_sgn = -1
+		i++
+	} else if s[i] == `+` {
+		exp_sgn = 1
+		i++
+	}
+
+	mut c := i
+	for c < s.len {
+		exp = exp * 10 + int(s[c]-`0`)
+		c++
+	}
+
+	// allocate exp+32 chars for the return string
+	mut res := []byte{len: exp+32, init: 0}
+	mut r_i := 0  // result string buffer index
+
+	//println("s:${sgn} b:${b[0]} es:${exp_sgn} exp:${exp}")
+	
+	if sgn == 1 {
+		if m_sgn_flag {
+			res[r_i] = `+`
+			r_i++
+		}
+	} else {
+		res[r_i] = `-`
+		r_i++
+	}
+
+	i = 0
+	if exp_sgn >= 0 {
+		for b[i] != 0 {
+			res[r_i] = b[i]
+			r_i++
+			i++
+			if i >= d_pos && exp >= 0 {
+				if exp == 0 {
+					res[r_i] = `.`
+					r_i++
+				}
+				exp--
+			}
+		}
+		for exp >= 0 {
+			res[r_i] = `0`
+			r_i++
+			exp--
+		}
+	} else {
+		mut dot_p := true
+		for exp > 0 {
+			res[r_i] = `0`
+			r_i++
+			exp--
+			if dot_p  {
+				res[r_i] = `.`
+				r_i++
+				dot_p = false
+			}
+		}
+		for b[i] != 0 {
+			res[r_i] = b[i]
+			r_i++
+			i++
+		}
+	}
+
+	// remove the dot form the numbers like 2.
+	if r_i > 1 && res[r_i-1] == `.` {
+		r_i--
+	}
+
 	res[r_i] = 0
 	return unsafe { tos(res.data,r_i) }
 }