Legacy Document

-

You can use the - symbol to subtract one real number from another.

x - y

x

Any floating-point number.

y

Any floating-point number.

DESCRIPTION

The - operator performs the standard subtraction of two floating-point numbers.

EXCEPTIONS

When x and y are both finite and nonzero, either the result of x - y is exact or it raises one of the following exceptions:

• inexact (if the result must be rounded or if an overflow or underflow occurs)
• overflow (if the result is outside the range of the data type)
• underflow (if the result is inexact and must be represented as a denormalized number or 0)

SPECIAL CASES

Table 6-4 shows the results when one of the operands of the subtraction operation is a zero, a NaN, or an Infinity. In this table, x is any floating-point number.

Table 6-4 Special cases for floating-point subtraction

Operation	Result	Exceptions raised
$x+-(+0)$	x	None
$(+0)+-x$	-x	None
$(+0)+-(-0)$	+0	None
$x+-(-0)$	x	None
$(-0)+-x$	-x	None
$(-0)+-(+0)$	$-0$	None
$(-0)+-(-0)$	+0	None
x - NaN	NaN	None[6]
NaN - x	NaN	None[6]
$x+-(+$ )	$-$	None
$(+$ )+-x	+	None
$(+$ )+-(+ )	NaN	Invalid
$x+-(-$ )	+	None
$(-$ )+-x	$-$	None
$(-$ )+-(- )	NaN	Invalid

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[6] If the NaN is a signaling NaN, the invalid exception is raised.