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strconv: cleanup atof.c.v - use a ParserState enum, clarify comments
This commit is contained in:
Delyan Angelov
parent
e4dfffd70b
commit
843ce43077
@ -1,26 +1,47 @@
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module strconv
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/*
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atof util
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// Copyright (c) 2019-2022 Dario Deledda. All rights reserved.
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// Use of this source code is governed by an MIT license
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// that can be found in the LICENSE file.
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//
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// This file contains utilities for converting a string to a f64 variable.
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// IEEE 754 standard is used.
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// Know limitation: limited to 18 significant digits
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//
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// The code is inspired by:
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// Grzegorz Kraszewski krashan@teleinfo.pb.edu.pl
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// URL: http://krashan.ppa.pl/articles/stringtofloat/
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// Original license: MIT
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// 96 bit operation utilities
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//
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// Note: when u128 will be available, these function can be refactored.
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Copyright (c) 2019-2022 Dario Deledda. All rights reserved.
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Use of this source code is governed by an MIT license
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that can be found in the LICENSE file.
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// f32 constants
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pub const (
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single_plus_zero = u32(0x0000_0000)
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single_minus_zero = u32(0x8000_0000)
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single_plus_infinity = u32(0x7F80_0000)
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single_minus_infinity = u32(0xFF80_0000)
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)
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This file contains utilities for convert a string in a f64 variable
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IEEE 754 standard is used
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// f64 constants
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pub const (
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digits = 18
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double_plus_zero = u64(0x0000000000000000)
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double_minus_zero = u64(0x8000000000000000)
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double_plus_infinity = u64(0x7FF0000000000000)
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double_minus_infinity = u64(0xFFF0000000000000)
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)
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Know limitation:
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- limited to 18 significant digits
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The code is inspired by:
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Grzegorz Kraszewski krashan@teleinfo.pb.edu.pl
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URL: http://krashan.ppa.pl/articles/stringtofloat/
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Original license: MIT
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96 bit operation utilities
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Note: when u128 will be available these function can be refactored
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*/
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// char constants
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pub const (
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c_dpoint = `.`
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c_plus = `+`
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c_minus = `-`
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c_zero = `0`
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c_nine = `9`
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c_ten = u32(10)
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)
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// right logical shift 96 bit
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fn lsr96(s2 u32, s1 u32, s0 u32) (u32, u32, u32) {
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@ -78,48 +99,7 @@ fn sub96(s2 u32, s1 u32, s0 u32, d2 u32, d1 u32, d0 u32) (u32, u32, u32) {
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return r2, r1, r0
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}
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// Constants
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pub const (
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//
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// f32 constants
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//
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single_plus_zero = u32(0x0000_0000)
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single_minus_zero = u32(0x8000_0000)
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single_plus_infinity = u32(0x7F80_0000)
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single_minus_infinity = u32(0xFF80_0000)
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//
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// f64 constants
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//
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digits = 18
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double_plus_zero = u64(0x0000000000000000)
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double_minus_zero = u64(0x8000000000000000)
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double_plus_infinity = u64(0x7FF0000000000000)
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double_minus_infinity = u64(0xFFF0000000000000)
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//
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// Possible parser return values.
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//
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parser_ok = 0 // parser finished OK
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parser_pzero = 1 // no digits or number is smaller than +-2^-1022
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parser_mzero = 2 // number is negative, module smaller
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parser_pinf = 3 // number is higher than +HUGE_VAL
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parser_minf = 4 // number is lower than -HUGE_VAL
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parser_invalid_number = 5 // invalid number, used for '#@%^' for example
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//
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// char constants
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// Note: Modify these if working with non-ASCII encoding
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//
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c_dpoint = `.`
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c_plus = `+`
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c_minus = `-`
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c_zero = `0`
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c_nine = `9`
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c_ten = u32(10)
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)
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// Utility functions
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// NOTE: Modify these if working with non-ASCII encoding
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fn is_digit(x byte) bool {
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return (x >= strconv.c_zero && x <= strconv.c_nine) == true
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}
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@ -132,14 +112,21 @@ fn is_exp(x byte) bool {
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return (x == `E` || x == `e`) == true
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}
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/*
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String parser
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NOTE: #TOFIX need one char after the last char of the number
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*/
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// Possible parser return values.
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enum ParserState {
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ok // parser finished OK
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pzero // no digits or number is smaller than +-2^-1022
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mzero // number is negative, module smaller
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pinf // number is higher than +HUGE_VAL
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minf // number is lower than -HUGE_VAL
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invalid_number // invalid number, used for '#@%^' for example
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}
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fn parser(s string) (int, PrepNumber) {
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// parser tries to parse the given string into a number
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// NOTE: #TOFIX need one char after the last char of the number
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fn parser(s string) (ParserState, PrepNumber) {
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mut digx := 0
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mut result := strconv.parser_ok
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mut result := ParserState.ok
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mut expneg := false
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mut expexp := 0
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mut i := 0
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@ -216,45 +203,45 @@ fn parser(s string) (int, PrepNumber) {
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pn.exponent += expexp
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if pn.mantissa == 0 {
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if pn.negative {
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result = strconv.parser_mzero
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result = .mzero
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} else {
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result = strconv.parser_pzero
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result = .pzero
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}
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} else if pn.exponent > 309 {
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if pn.negative {
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result = strconv.parser_minf
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result = .minf
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} else {
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result = strconv.parser_pinf
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result = .pinf
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}
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} else if pn.exponent < -328 {
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if pn.negative {
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result = strconv.parser_mzero
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result = .mzero
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} else {
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result = strconv.parser_pzero
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result = .pzero
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}
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}
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if i == 0 && s.len > 0 {
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return strconv.parser_invalid_number, pn
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return ParserState.invalid_number, pn
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}
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return result, pn
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}
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/*
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Converter to the bit form of the f64 number
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*/
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// converter return a u64 with the bit image of the f64 number
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// converter returns a u64 with the bit image of the f64 number
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fn converter(mut pn PrepNumber) u64 {
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mut binexp := 92
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mut s2 := u32(0) // 96-bit precision integer
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// s0,s1,s2 are the parts of a 96-bit precision integer
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mut s2 := u32(0)
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mut s1 := u32(0)
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mut s0 := u32(0)
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mut q2 := u32(0) // 96-bit precision integer
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// q0,q1,q2 are the parts of a 96-bit precision integer
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mut q2 := u32(0)
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mut q1 := u32(0)
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mut q0 := u32(0)
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mut r2 := u32(0) // 96-bit precision integer
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// r0,r1,r2 are the parts of a 96-bit precision integer
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mut r2 := u32(0)
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mut r1 := u32(0)
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mut r0 := u32(0)
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//
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mask28 := u32(u64(0xF) << 28)
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mut result := u64(0)
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// working on 3 u32 to have 96 bit precision
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@ -404,35 +391,30 @@ fn converter(mut pn PrepNumber) u64 {
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return result
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}
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// Public functions
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// atof64 return a f64 from a string doing a parsing operation
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// atof64 parses the string `s`, and if possible, converts it into a f64 number
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pub fn atof64(s string) ?f64 {
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if s.len == 0 {
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return error('expected a number found an empty string')
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}
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mut pn := PrepNumber{}
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mut res_parsing := 0
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mut res := Float64u{}
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res_parsing, pn = parser(s)
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mut res_parsing, mut pn := parser(s)
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match res_parsing {
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strconv.parser_ok {
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.ok {
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res.u = converter(mut pn)
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}
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strconv.parser_pzero {
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.pzero {
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res.u = strconv.double_plus_zero
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}
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strconv.parser_mzero {
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.mzero {
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res.u = strconv.double_minus_zero
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}
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strconv.parser_pinf {
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.pinf {
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res.u = strconv.double_plus_infinity
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}
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strconv.parser_minf {
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.minf {
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res.u = strconv.double_minus_infinity
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}
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else {
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.invalid_number {
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return error('not a number')
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}
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}
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