Comparative expressions
Comparative expressions are a subdomain of the Logical expressions and return a truth value ('true' or 'false'). The following operators can be used for comparative expressions:
- greater than '>'
- less than '<'
- greater than or equal to '>='
- less than or equal to '<='
- equal to '=='
- not equal to '!=='
Comparative operations can be used within the template syntax. One option for output them is by using the instruction $CMS_VALUE(...)$.
'==' operator
The check for equality can be carried out using the operator '=='.
a==b
The evaluation of the expression checks whether a equals b.
Example:
$CMS_SET(a, 2)$
$CMS_SET(b, a)$
$CMS_VALUE(a==b)$
returns the value 'true'.
'!=' operator
The check for inequality can be carried out using the operator '!=='.
a!=b
The evaluation of the expression checks whether a is not equal to b.
Example:
$CMS_SET(a, 2)$
$CMS_SET(b, a)$
$CMS_VALUE(a!=b)$
returns the value 'false'.
'<' operator
The check for "less than" can be carried out using the operator '<'.
a<b
The evaluation of the expression checks whether a is less than b.
Example:
$CMS_SET(a,2)$
$CMS_SET(b,a)$
$CMS_VALUE(a<b)$
returns the value 'false'.
'<=' operator
The check for "less than or equal to" can be carried out using the operator '<='.
a<=b
The evaluation of the expression checks whether a is less than b or whether a is equal to b. If one of the conditions applies the expression returns the value 'true'.
Example:
$CMS_SET(a,2)$
$CMS_SET(b,a)$
$CMS_VALUE(a<=b)$
returns the value 'true'.
'>' operator
The check for "greater than" can be carried out using the operator '>'.
a<b
The evaluation of the expression checks whether a is greater than b.
Example:
$CMS_SET(a,2)$
$CMS_SET(b,a)$
$CMS_VALUE(a>b)$
returns the value 'false'.
'>=' operator
The check for "greater than or equal to" can be carried out using the operator '>='.
a>=b
The evaluation of the expression checks whether a is greater than b or whether a is equal to b. If one of the conditions applies the expression returns the value 'true'.
Example:
$CMS_SET(a,2)$
$CMS_SET(b,a)$
$CMS_VALUE(a>=b)$
returns the value 'true'.
Operator precedence
In FirstSpirit combinations of several operators within logical or comparative expressions are evaluated, like in other programming languages (e.g. Java), in a specific order.
In a logical AND operation (conjunction) a && b b is not evaluated if a returns already the Boolean value 'false'. In a logical OR operation (disjunction) a || b b is not evaluated if a returns already the Boolean value 'true'.
In addition there is a ranking order of operators: Comparative expressions ("==", "!=", "<", ">", "<=", ">=") have higher precedence than Logical expressions ("&&", "||"). This means that comparative expressions are evaluated before logical expressions, special use of parentheses is not necessary.
Furthermore, within comparative expressions the operators "<", ">", "<=" and ">=" have higher precedence than the operators "==" and "!=" and are evaluated first. Within the logical expressions "&&" has higher precedence than "||".
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Before logical and comparative expressions are evaluated, first of all Arithmetical operations are performed. Consequently the following operator precedence results:
Operators with the same precedence are evaluated from left to right. Using parentheses can alter the order of evaluation determined by operator precedence. |
Example:
The text "The value of the variable a begins with b or B." is to be output if a is not null and the value (here Ball) begins with the character "b" (in upper or lower case).
$CMS_SET(a, "Ball")$
$CMS_IF(a != null && a.charAt(0).toString.lowerCase == "b")$
The value of the variable a begins with b or B.
$CMS_END_IF$
In this example the expression a != null as well as the expression a.charAt(0).toString.lowerCase == "b" return the Boolean value 'true'. Result: The text will be output.
In a second example the text "The value of the variable a begins with b or B." is to be output if a is not null and the value begins with the character "b" (in upper or lower case).
$CMS_SET(a, null)$
$CMS_IF(a != null && a.charAt(0).toString.lowerCase == "b")$
The value of the variable a begins with b or B.
$CMS_END_IF$
In this case the text will not be output because first the expression a != null is evaluated. It returns the value 'false' so that the operator with the lower priority (here: &&) takes no effect at all.