2.1.16.1.6 is_equal

Description

Compare two double values and see if they are equal or not.

Syntax

BOOL is_equal( double x, double y, int nCode = '=' )

Parameters

x

[input] first compare value

y

[input] second compare value

nCode

[input] '=' for testing equality, '!' for testing inequality, any other value will return FALSE.

Return

Return true if equal when testing equality or unequal when testing inequality, else false.

Examples

EX1

void    is_equal_ex1()
{
    double        a = 1.;
    
    // add 1.e-17:
    a += 1.e-17;
    
    // Compare with 1.:
    if (is_equal(a, 1.))
    {
        // If @ND still has the default value, which is 1.e-16, this will be true.
        out_str("a is 1.");
    }
    else
    {
        out_str("a is not 1.");
    }
    
    // add 1.e-14
    a += 1.e-14;
    if (is_equal(a, 1.))
    {
        // If @ND still has the default value, which is 1.e-16, this will be false.
        out_str("a is 1.");
    }
    else
    {
        out_str("a is not 1.");
    }
}

Remark

compare two double values and see if they are equal or not equal in the same sense as in LabTalk.

This function uses the LabTalk system variable @ND to test if (abs(x)-abs(y))/((abs(x)+abs(y)) is less then @ND or not. If @ND = 0, it does standard arithmetic comparison x == y.

See Also

Header to Include

origin.h

Reference