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      trunc, truncf, truncl

      From cppreference.com
      <c‎ |numeric‎ |math
       
       
       
      Common mathematical functions
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      Nearest integer floating-point
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      trunc
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      Defined in header<math.h>
      float       truncf(float arg);
      (1)(since C99)
      double      trunc(double arg);
      (2)(since C99)
      longdouble truncl(longdouble arg);
      (3)(since C99)
      Defined in header<tgmath.h>
      #define trunc( arg )
      (4)(since C99)
      1-3) Computes the nearest integer not greater in magnitude thanarg.
      4) Type-generic macro: Ifarg has typelongdouble,truncl is called. Otherwise, ifarg has integer type or the typedouble,trunc is called. Otherwise,truncf is called.

      Contents

      [edit]Parameters

      arg - floating-point value

      [edit]Return value

      If no errors occur, the nearest integer value not greater in magnitude thanarg (in other words,arg rounded towards zero), is returned.

      Return value
      math-trunc.svg
      Argument

      [edit]Error handling

      Errors are reported as specified inmath_errhandling.

      If the implementation supports IEEE floating-point arithmetic (IEC 60559):

      • The currentrounding mode has no effect.
      • Ifarg is ±∞, it is returned, unmodified.
      • Ifarg is ±0, it is returned, unmodified.
      • Ifarg is NaN, NaN is returned.

      [edit]Notes

      FE_INEXACT may be (but isn't required to be) raised when truncating a non-integer finite value.

      The largest representable floating-point values are exact integers in all standard floating-point formats, so this function never overflows on its own; however the result may overflow any integer type (includingintmax_t), when stored in an integer variable.

      The implicit conversion from floating-point to integral types also rounds towards zero, but is limited to the values that can be represented by the target type.

      [edit]Example

      Run this code
      #include <math.h>#include <stdio.h> int main(void){printf("trunc(+2.7) = %+.1f\n", trunc(+2.7));printf("trunc(-2.7) = %+.1f\n", trunc(-2.7));printf("trunc(-0.0) = %+.1f\n", trunc(-0.0));printf("trunc(-Inf) = %+f\n",   trunc(-INFINITY));}

      Possible output:

      trunc(+2.7) = +2.0trunc(-2.7) = -2.0trunc(-0.0) = -0.0trunc(-Inf) = -inf

      [edit]References

      • C23 standard (ISO/IEC 9899:2024):
      • 7.12.9.8 The trunc functions (p: TBD)
      • 7.25 Type-generic math <tgmath.h> (p: TBD)
      • F.10.6.8 The trunc functions (p: TBD)
      • C17 standard (ISO/IEC 9899:2018):
      • 7.12.9.8 The trunc functions (p: TBD)
      • 7.25 Type-generic math <tgmath.h> (p: TBD)
      • F.10.6.8 The trunc functions (p: TBD)
      • C11 standard (ISO/IEC 9899:2011):
      • 7.12.9.8 The trunc functions (p: 253-254)
      • 7.25 Type-generic math <tgmath.h> (p: 373-375)
      • F.10.6.8 The trunc functions (p: 528)
      • C99 standard (ISO/IEC 9899:1999):
      • 7.12.9.8 The trunc functions (p: 234)
      • 7.22 Type-generic math <tgmath.h> (p: 335-337)
      • F.9.6.8 The trunc functions (p: 464)

      [edit]See also

      computes largest integer not greater than the given value
      (function)[edit]
      (C99)(C99)
      computes smallest integer not less than the given value
      (function)[edit]
      (C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)(C99)
      rounds to nearest integer, rounding away from zero in halfway cases
      (function)[edit]
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