## MA01CD

### 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).

```
```  None
```
Example

Program Text

```  None
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Program Data
```  None
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Program Results
```  None
```