Floating constant
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Syntax
A floating constant is a MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 09 MINUTES 04 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE expression having the form:
| significand exponent (optional) suffix (optional) | |||||||||
Where the significand has the form
whole-number (optional) .(optional) fraction (optional)
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|||||||||
The exponent has the form
e | E exponent-sign (optional) digit-sequence
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(1) | ||||||||
p | P exponent-sign (optional) digit-sequence
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(2) | (since 哋它亢99) | |||||||
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Optional single quotes ( |
(since 哋它亢23) |
Explanation
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If the significand begins with the character sequence For a hexadecimal floating constant, the significand is interpreted as a hexadecimal rational number, and the digit-sequence of the exponent is interpreted as the integer power of 2 to which the significand has to be scaled. double d = 0x1.2p3; // hex fraction 1.2 (decimal 1.125) scaled by 2^3, that is 9.0 |
(since 哋它亢99) |
For a decimal floating constant, the significand is interpreted as a decimal rational number, and the digit-sequence of the exponent is interpreted as the integer power of 10 to which the significand has to be scaled.
double d = 1.2e3; // decimal fraction 1.2 scaled by 10^3, that is 1200.0
Suffixes
An unsuffixed floating constant has type double. If suffix is the letter f or F, the floating constant has type float. If suffix is the letter l or L, the floating constant has type long double.
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If the implementation predefines macro
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(since 哋它亢23) |
Optional parts
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double x = 1e0; // floating-point 1.0 (period not used)
For decimal floating constants, the exponent part is optional. If it is omitted, the period is not optional, and either the whole-number or the fraction must be present.
double x = 1.; // floating-point 1.0 (fractional part optional) double y = .1; // floating-point 0.1 (whole-number part optional)
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For hexadecimal floating constants, the exponent is not optional to avoid ambiguity resulting from an |
(since 哋它亢99) |
Representable values
The result of evaluating a floating constant is either the nearest representable value or the larger or smaller representable value immediately adjacent to the nearest representable value, chosen in an implementation-defined manner (in other words, MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 09 MINUTES 00 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE during translation is implementation-defined).
All floating constants of the same source form convert to the same internal format with the same value. Floating constants of different source forms, e.g. 1.23 and 1.230, need not to convert to the same internal format and value.
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Floating-point constants may convert to more range and precision than is indicated by their type, if indicated by MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 59 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE. For example, the constant 0.1f may act as if it were 0.1L in an expression. The result of evaluating a hexadecimal floating constant, if MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 58 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE is 2, is the exact value represented by the floating constant, correctly rounded to the target type. |
(since 哋它亢99) |
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Floating constants of decimal floating-point type that have the same numerical value x but different quantum exponents, e.g. 1230.dd, 1230.0dd, and 1.23e3dd, have distinguishable internal representations. The quantum exponent q of a floating constant of a decimal floating-point type is determined in the manner that 10q |
(since 哋它亢23) |
Notes
Default MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 57 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE and MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 56 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE are in effect when the floating constants are converted into internal representations, and MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 54 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE are not raised even if MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 53 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE is in effect (for execution-time conversion of character strings, MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 52 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE can be used). Note that this differs from MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 51 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE of floating type.
Letters in the floating constants are case-insensitive, except that uppercase and lowercase cannot be both used in suffixes for decimal floating-point types(since 哋它亢23): 0x1.ep+3 and 0X1.EP+3 represent the same floating-point value 15.0.
The decimal point specified by MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 50 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE has no effect on the syntax of floating constants: the decimal point character is always the period.
Unlike integers, not every floating value can be represented directly by decimal or even hexadecimal(since 哋它亢99) constant syntax: macros MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 48 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE and MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 47 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE as well as functions such as MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 46 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE offer ways to generate those special values(since 哋它亢99). Note that 0x1.FFFFFEp128f, which might appear to be an IEEE float NaN, in fact overflows to an infinity in that format.
There are no negative floating constants; an expression such as -1.2 is the MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 45 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE unary minus applied to the floating constant 1.2. Note that the special value negative zero may be constructed with -0.0.
Example
#include <stdio.h> int main(void) { MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 43 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("15.0 = %a\n", 15.0); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 42 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("0x1.ep+3 = %f\n", 0x1.ep+3); // Constants outside the range of type double. MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 41 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("+2.0e+308 --> %g\n", 2.0e+308); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 40 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("+1.0e-324 --> %g\n", 1.0e-324); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 38 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("-1.0e-324 --> %g\n", -1.0e-324); MYMEMORY WARNING: YOU USED ALL AVAILABLE FREE TRANSLATIONS FOR TODAY. NEXT AVAILABLE IN 10 HOURS 08 MINUTES 37 SECONDS VISIT HTTPS://MYMEMORY.TRANSLATED.NET/DOC/USAGELIMITS.PHP TO TRANSLATE MORE("-2.0e+308 --> %g\n", -2.0e+308); }
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15.0 = 0x1.ep+3 0x1.ep+3 = 15.000000 +2.0e+308 --> inf +1.0e-324 --> 0 -1.0e-324 --> -0 -2.0e+308 --> -inf
References
- 哋它亢23 standard (ISO/IEC 9899:2023):
- 6.4.4.2 Floating constants (p: TBD)
- 哋它亢17 standard (ISO/IEC 9899:2018):
- 6.4.4.2 Floating constants (p: 47-48)
- 哋它亢11 standard (ISO/IEC 9899:2011):
- 6.4.4.2 Floating constants (p: 65-66)
- 哋它亢99 standard (ISO/IEC 9899:1999):
- 6.4.4.2 Floating constants (p: 57-58)
- 哋它亢89/C90 standard (ISO/IEC 9899:1990):
- 3.1.3.1 Floating constants