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Safely computing the sign of a sum of two real numbers represented using integer powers of a base

**[Specification]**
**[Arguments]**
**[Method]**
**[References]**
**[Comments]**
**[Example]**
**Purpose**

To compute, without over- or underflow, the sign of the sum of two
real numbers represented using integer powers of a base (usually,
the machine base). Any base can be used, but it should the same
for both numbers. The result is an integer with value 1, 0, or -1,
depending on the sum being found as positive, zero, or negative,
respectively.

**Specification**
INTEGER FUNCTION MA01CD( A, IA, B, IB )
C .. Scalar Arguments ..
INTEGER IA, IB
DOUBLE PRECISION A, B

**Function Value**
MA01CD INTEGER
The sign of the sum of the two numbers, which is usually
either 1, or -1. If both numbers are 0, or if they have
the same exponent and their sum is 0, the returned value
is 0.

**Arguments**
**Input/Output Parameters**

A (input) DOUBLE PRECISION
The first real scalar.
IA (input) INTEGER
Exponent of the base for the first real scalar. The scalar
is represented as A * BASE**(IA).
B (input) DOUBLE PRECISION
The first real scalar.
IB (input) INTEGER
Exponent of the base for the first real scalar. The scalar
is represented as B * BASE**(IB).

**Further Comments**
None

**Example**
**Program Text**

None

**Program Data**
None

**Program Results**
None

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