---
title: "init(_:)"
framework: swift
role: symbol
role_heading: Initializer
path: "swift/float/init(_:)-h2f4"
---

# init(_:)

Creates a new instance from the given string.

## Declaration

```swift
init?<S>(_ text: S) where S : StringProtocol
```

## Parameters

- `text`: An input string to convert to a Float? instance.

## Discussion

Discussion The string passed as text can represent a real number in decimal or hexadecimal format or can be in a special format representing infinity or NaN (“not a number”). If text is not in a recognized format, the optional initializer will fail and return nil. The text string consists of an optional plus or minus sign character (+ or -) followed by one of the following: A decimal string contains a significand consisting of one or more decimal digits that may include a decimal point: let c = Float("-1.0") // c == -1.0

let d = Float("28.375") // d == 28.375 A decimal string may also include an exponent following the significand, indicating the power of 10 by which the significand should be multiplied. If included, the exponent is separated by a single character, e or E, and consists of an optional plus or minus sign character and a sequence of decimal digits. let e = Float("2837.5e-2") // e == 28.375 A hexadecimal string contains a significand consisting of 0X or 0x followed by one or more hexadecimal digits that may include a decimal point. let f = Float("0x1c.6") // f == 28.375 A hexadecimal string may also include an exponent indicating the power of 2 by which the significand should be multiplied. If included, the exponent is separated by a single character, p or P, and consists of an optional plus or minus sign character and a sequence of decimal digits. let g = Float("0x1.c6p4") // g == 28.375 The input strings "inf" or "infinity" (case insensitive) are converted to an infinite result: let i = Float("inf") // i == Float.infinity

let j = Float("-Infinity") // j == -Float.infinity An input string of "nan" (case insensitive) is converted into a NaN value: let n = Float("-nan") // n?.isNaN == true // n?.sign == .minus A NaN string may also include a payload in parentheses following the "nan" keyword. The payload consists of a sequence of decimal digits, or the characters 0X or 0x followed by a sequence of hexadecimal digits. If the payload contains any other characters, it is ignored. If the value of the payload is larger than can be stored as the payload of a Float.nan, the least significant bits are used. let p = Float("nan(0x10)") // p?.isNaN == true // String(p!) == "nan(0x10)" An input string of "snan" (case insensitive) is converted into a signaling NaN value.  This form permits an optional payload in the same format as for a non-signaling NaN. A string in any other format than those described above or containing additional characters results in a nil value. For example, the following conversions result in nil:   Float(" 5.0")      // Includes whitespace   Float("±2.0")      // Invalid character   Float("0x1.25e4")  // Incorrect exponent format A decimal or hexadecimal string is converted to a Float instance using the IEEE 754 roundTiesToEven (default) rounding attribute. Values with absolute value smaller than one-half of Float.leastNonzeroMagnitude are rounded to plus or minus zero. Values with absolute value larger than Float.greatestFiniteMagnitude are rounded to plus or minus infinity.   let y = Float("1.23e-9999")   // y == 0.0   // y?.sign == .plus

let z = Float("-7.89e-7206")   // z == -0.0   // z?.sign == .minus

let r = Float("1.23e17802")   // r == Float.infinity

let s = Float("-7.89e7206")   // s == Float.-infinity note: Prior to Swift 5.4, a decimal or hexadecimal input string whose value was too large to represent as a finite Float instance returned nil instead of Float.infinity.

## See Also

### Converting Strings

- [init(_:)](swift/float/init(_:)-4xsj6.md)