parse(text: string) -- Модуль
- std.
decimal → - Получатель
- Неприменимо
- Минимальное число аргументов
- 1
- Максимальное число аргументов
- 1
Declaration and parameters
СсылкаДоступность
Включено по умолчанию · Не определено
Import std.decimal in language mode 5.21.
The current compiler selects std/decimal.tpz for this language mode. Availability in other released editions and inclusion in each installed distribution are Pending.
Получатель
Ограничения параметров
Decimal.parse reads the complete input string. Text starts with an optional ASCII plus or minus sign. The remaining text contains ASCII digits and at most one decimal point.
Without a decimal point, at least one digit is required. With a decimal point, at least one digit must follow it and the integer digits may be absent. The strings .5 and -.5 are accepted. The strings 1. and . are rejected.
Leading integer zeros and trailing fractional zeros are accepted. Their exact numeric value is normalized by the decimal value rule. An accepted sign on zero does not survive normalization.
The input may contain at most 4294967295 fractional digits before normalization. A larger fractional digit count returns None(). The integer digit count has no fixed numeric precision limit.
Whitespace, non-ASCII digits, separators, radix prefixes, exponents, NaN and infinity spellings are rejected. Parsing does not trim, remove separators, stop at a valid prefix, or convert through a binary float.
Valid text returns Some containing the exact Decimal. Every malformed spelling returns None() without a numeric conversion fault or replacement value.
This grammar describes text data passed to Decimal.parse. Numeric literal spelling follows the language literal rules.
Связанное правило · Parse complete finite decimal text →Результат
The declared result type is Option<Decimal>.
Эффекты
Ошибки
Result and effects
СсылкаAccept an optional plus or minus sign, ASCII digits and an optional decimal point followed by digits. A missing integer part is accepted. Invalid text or too many fractional digits returns None().
Why
СсылкаComplete input parsing preserves exact decimal data and makes malformed spellings visible.
Resolved contracts
СсылкаRelated entries
СсылкаParse complete finite decimal text
СсылкаParse complete finite decimal text
Decimal.parse reads the complete input string. Text starts with an optional ASCII plus or minus sign. The remaining text contains ASCII digits and at most one decimal point.
Without a decimal point, at least one digit is required. With a decimal point, at least one digit must follow it and the integer digits may be absent. The strings .5 and -.5 are accepted. The strings 1. and . are rejected.
Leading integer zeros and trailing fractional zeros are accepted. Their exact numeric value is normalized by the decimal value rule. An accepted sign on zero does not survive normalization.
The input may contain at most 4294967295 fractional digits before normalization. A larger fractional digit count returns None(). The integer digit count has no fixed numeric precision limit.
Whitespace, non-ASCII digits, separators, radix prefixes, exponents, NaN and infinity spellings are rejected. Parsing does not trim, remove separators, stop at a valid prefix, or convert through a binary float.
Valid text returns Some containing the exact Decimal. Every malformed spelling returns None() without a numeric conversion fault or replacement value.
This grammar describes text data passed to Decimal.parse. Numeric literal spelling follows the language literal rules.
Причина
A complete decimal data grammar makes accepted input predictable and preserves every digit. Optional signs and a missing integer zero are accepted input conventions. Canonical output still gives each value one serialized spelling.
Accept explicit signs and fractional decimal text
Ссылкаimport std.decimal { Decimal }import std.testimport std.iofunction read(text: string) -> Decimal {let parsed: Option<Decimal> = Decimal.parse(text)let value: Decimal = test.assertSome(parsed)return value}for text in (["7", "+7", "-7", "0007", ".5", "-.5", "+.5", "01.0200"]) {let value: Decimal = read(text)io.writeLine(value.toString())}
7
7
-7
7
0.5
-0.5
0.5
1.02
Ожидаемый результат
Ожидаемый результат
Выполнение завершается. Код завершения 0.
77-770.5-0.50.51.02
Reject incomplete and nondecimal spellings
Ссылкаimport std.decimal { Decimal }import std.iofor text in (["", "+", "-", ".", "+.", "-.", "1.", "1.2.3", "1e2", "1E+2", "0x10", "1_000", "1,2", "NaN", "Infinity", " 1", "1 ", "１.２", "١.٢", "1\n2", "\t1"]) {match (Decimal.parse(text)) {case None() => io.writeLine("rejected")case Some(_) => io.writeLine("accepted")}}
rejected
rejected
rejected
rejected
rejected
rejected
rejected
rejected
rejected
rejected
rejected
rejected
rejected
rejected
rejected
rejected
rejected
rejected
rejected
rejected
rejected
Ожидаемый результат
Ожидаемый результат
Выполнение завершается. Код завершения 0.
rejectedrejectedrejectedrejectedrejectedrejectedrejectedrejectedrejectedrejectedrejectedrejectedrejectedrejectedrejectedrejectedrejectedrejectedrejectedrejectedrejected