Comparison Functions

The comparison operators (<, <=, >, >=) work for numbers, strings, and matrices. For matrices, they produce a matrix of results. If you compare mixed arguments, such as strings with numbers or matrices, the result is a missing value. Comparisons involving lists are not allowed and also return missing values.

The equality operators (== and !=) work for numbers, strings, matrices, and lists. For matrices, they produce a matrix of results; for lists, they produce a single result. If you test equality of mixed results (for example. strings with numbers or matrices) the result is 0 or unequal.

Range check operators let you check whether something falls between two specified values:

a = 1;

Show( 1 <= a < 3 );

b = 2;

Show( 2 < b <= 3 );

1 <= a < 3 = 1;

2 < b <= 3 = 0;

Expressions with comparison operators are evaluated all at once, not in sequence

All the comparison operators are eliding operators. That means JMP treats arguments joined by comparison operators as one big clause, as opposed to the way most expressions are evaluated one operator at a time. Evaluating as a single clause produces different results than the more usual method of evaluating in pieces. For example, the following two statements are different:

12 < a < 13;

(12 < a) < 13;

The first statement checks whether a is between 12 and 13, because all three arguments and both operators are read and evaluated together. The second statement uses parentheses to regroup the operations explicitly to evaluate from left to right, which would be the normal way to evaluate most expressions. Thus it first checks whether 12 is less than a, returning 1 if true or 0 if false. Then it checks whether the result is less than 13, which is always true because 0 and 1 are both less than 13.

All the comparison operators are elided when they are used in matched pairs or in the unmatched pairs <... <= and <=... <. What this means is that if you want a comparison statement to be evaluated one comparison operator at a time, you should use parentheses ( ) to control the order of operations explicitly.

Equal(a, b, ...)

a==b==...

Description

Compares all the listed values and tests if they are all equal to each other.

Returns

1 (true) if all arguments evaluate to the same value.

0 (false) otherwise.

Arguments

Two or more variables, references, matrices, or numbers.

Notes

If more than two arguments are specified, a 1 is returned only if all arguments are exactly the same. This is typically used in conditional statements and to control loops.

The comparison is case-sensitive for string comparisons.

Greater(a, b, ...)

a>b>...

Description

Compares all the list values and tests if, in each pair, the left value is greater than the right.

Returns

1 (true) if a evaluates strictly greater than b (and b evaluates strictly greater than c, and so on).

0 (false) otherwise.

Arguments

Two or more variables, references, matrices, or numbers.

Notes

If more than two arguments are specified, a 1 is returned only if each argument is greater than the one that follows it. This is typically used in conditional statements and to control loops.

Greater, Less, GreaterOrEqual, and LessOrEqual can also be strung together. If you do not group with parentheses, JMP evaluates each pair left to right. You can also use parentheses to explicitly tell JMP how to evaluate the expression.

Greater or Equal(a, b, ...)

a>=b>=...

Description

Compares all the list values and tests if, in each pair, the left value is greater than or equal to the right.

Returns

1 (true) if a evaluates strictly greater than or equal to b (and b evaluates strictly greater than or equal to c, and so on).

0 (false) otherwise.

Arguments

Two or more variables, references, matrices, or numbers.

Notes

If more than two arguments are specified, a 1 is returned only if each argument is greater than or equal to the one that follows it. This is typically used in conditional statements and to control loops.

Is Missing(expr)