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floattolong

Coerces values of type float to values of type long.

Prototype

	function floattolong (
		float_val  : float   
	)

	return_val [dimsizes(float_val)] :  long

Arguments

float_val

A float variable of any dimension.

Return value

Returns longs obtained by truncating any fractional part of the input values. The dimensionality of the output matches that of the input.

Description

This function converts float values to long values by truncating any fractional part of the input values.

For example:
    -1.9 is truncated to -1
    -1.1 is truncated to -1
     2.1 is truncated to 2
    2.9 is truncated to 2.

On most machines longs are 32-bit quantities, the same as integers. On 64-bit machines, longs are sometimes 64-bit quantities.

Any input value that is out of range for a long is returned as a missing value.

This function performs coercion that is not automatically available through the NCL grammar. See the section on coercion of types for details on NCL's automatic type conversions.

Attributes, with the exception of _FillValue, are not propagated by the conversion functions. See Example 2 below.

Special considerations apply to how missing values and out-of-range values are handled in the conversion functions. For this function an out-of-range value is a valid float that is not in the valid range of a long, or a numeric value that is outside the range of a valid long. An out-of-range value is converted to a missing value, but what that missing value is depends on the circumstances of the particular conversion being performed. For example, determination has to be made whether a missing value for a variable to be converted is in the range of the type of the target variable. Example 2 below illustrates most of the many possibilities; its output should provide convincing evidence that care must be taken when making assumptions about the results returned from a conversion function when the original variable has missing or out-of-range values.

See Also

floattointeger, floattobyte, floattoshort, tolong

Examples

Example 1

Converts an array of floats to longs.


begin
  a = (/ -1.123456712345, -1.91234567891234, 2.823456712345, 22. /)
  print(floattolong(a))
end

Example 2

Shows how missing values and out-of-range values are handled.


begin
;
;  Conversion does not preserve attributes, except missing value.
;
  a = (/ -1.1, 2.5, 3.9/)
  a@T = "string"
  a@_FillValue = -444.
  b = floattolong(a)
  print (b)
  delete(a)
  delete(b)
;
;  The missing value of the target variable is retained if
;  the missing value of the original variable is out of
;  the range of the target variable.  Note that this can
;  turn a value that is not a missing value in the original
;  variable into a missing value in the target variable if
;  a value in the original variable equals the missing value
;  in the target variable.  For example, if -444. were a
;  value in "a" below, it would become a missing value in "b".
;
  a = (/ -1, -2., 3./)
  a@_FillValue = 1.e40
  b = new(3,long)
  b@_FillValue = -444
  b = floattolong(a)
  print (b)
  delete(a)
  delete(b)
;
;  Values to be converted that are out of the range
;  of the target variable are converted to the default missing value
;  of the target variable if neither the original variable nor
;  the target variable has a missing value specified.
;
  a = (/ -1, 2., 3.e20/)
  b = floattolong(a)
  print (b)
  delete(a)
  delete(b)
;
;  Values to be converted that are out of the range
;  of the target variable are converted to the missing value
;  of the original variable, if that missing value is in
;  the range of the target variable and the target variable
;  has no missing value specified.
;
  a = (/ -1, 2., 3.e20/)
  a@_FillValue = -444.
  b = floattolong(a)
  print (b)
  delete(a)
  delete(b)
;
;  Values to be converted that are out of the range
;  of the target variable are converted to the missing value
;  of the target variable if the missing value of the
;  original variable is out of the range of the target variable
;  and the target variable has no missing value specified.
;
  a = (/ -1, 2., 3.e20/)
  a@_FillValue = 1.e50
  b = floattolong(a)
  print (b)
  delete(a)
  delete(b)
;
;  If the target variable has no missing value
;  specified, the missing value of the target
;  variable inherits the missing value of the
;  original variable and the missing values
;  of the original variable are retained in
;  the target variable.
;
  a = (/ -1, 2., -444./)
  a@_FillValue = -444.
  b = floattolong(a)
  print (b)
  delete(a)
  delete(b)
;
;  If the target variable has a missing
;  value specified and the original variable
;  has a missing value specified, the missing
;  value of the target variable is retained
;  even when the missing value of the original 
;  variable is in the range of the type of the 
;  target variable.  Missing values in the
;  original variable are converted to the 
;  missing value of the target variable.
;
  a = (/ -1, 2., -444./)
  a@_FillValue = -444.
  b = new(3,long,-666)
  b = floattolong(a)
  print (b)
  delete(a)
  delete(b)
end