Relational operators

Description

Relational refers to the relationship one value can have with another. For example, is one value equal (=) to another value? Or, is one value greater than (>) another value? The relational operators produce a result that is either true (1) or false (0).

The JB relational operators list:

Operator		Meaning
>		greater than
<		less than
>=		greater than or equal to
<=		less than or equal to
=		equal
<>		not equal

Syntax

expression operator expression

Expressions compared should be of the same type (both strings or both numeric).

For details on string comparison order (> < >= <=), see String comparison.

Result is boolean (logical). For JB, result happens to be 1 for TRUE and 0 for FALSE.

Hints

They are normally used as a condition in conditional statements and loops.

The fact that the result of relational operators is strictly 0 or 1 allows some hacks and shortcuts, see Useful Procedures

When comparing, if one of the numbers is a double-precision floating point number, and second number is an integer, both will be converted to double-precision. This could bring unexpected results or overflow error, see Examples.

Example

When comparing, if one of numbers is double and second integer, both converted to double.

This could show values equal if difference exceeds double precision (16 digits)

longInt=12345678901234567890  '20 digits
  fmt$="####################"  'format for using
doubleVal = longInt + 0.1   'adding fraction will make number double
print doubleVal         'double prints in exponential form, 1.23456789e19
'now print initial longInt and doubleVal using fmt$
print longInt                   '12345678901234567890
print using(fmt$,doubleVal)     '12345678901234567168
'They are obviously not equal
'BUT
if longInt>doubleVal then print "more"
if longInt=doubleVal then print "equal"
if longInt<doubleVal then print "less"
'prints "equal"

'BECAUSE when comparing, both values were converted to double (16 digits only)

Also, if comparing long integer with double, we can get runtime error - float overflow exception.

longInt = 10^400
Int2 = 10
double = 2.5

print longInt>Int2        'both integer - Ok
print Int2>double        'small integer, converts to double - Ok
print longInt>double    'JB tries to convert longInt to double - get float overflow exception (double range about +/-1e307)

Useful Procedures

'returns 0 for 0, 1 otherwise (that is, normalized TRUE or FALSE)
function normalize(num)
    normalize=num<>0
end function

'sign function: +1 for x>0, 0 for x=0, -1 for x<0
function sign(x)
    sign = (x>0) - (x<0)
end function