The Dollar and Semicolon Expression Operators

The dollar and semicolon expression operators allow for more advanced syntax constructs.

$-operator

The $-operator is an alias for the buffer.get() vipermethod. It must be followed by a buffer name. The buffer name can optionally be enclosed in quotes. When using quotes, you have the possibility of including the buffer scope.

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$varname is equivalent to buffer.get(varname) $'varname' is equivalent to buffer.get('varname') $'page:varname' is equivalent to buffer.get('page:varname') which can also be written as buffer.get('varname, page)

Example usage:

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{buffer.set(a,16)} <se:if expression="$a GT 10">Greater than 10</se:if> => Greater than 10 {sys.eval( $a * 4 )} => 64

;-operator

The ;-operator is a statement separator. It can be used to separate multiple expressions. Only the expression to the right of the semicolon will be used for the expression result. The left part of the expression can be used to manipulate internal state.

The left part of the expression is always be executed before the right part.

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{sys.eval(buffer.set(a,3); math.pow($a,2) + math.pow($a+1,2) )} => 25 {sys.eval(buffer.set(a,3); (buffer.get(a)+1) * buffer.get(a) )} => 12 {sys.eval(buffer.set(a,3); ($a+1) * $a )} => 12

Viper syntax constraints

Note that a viper is defined as a single vipermethod enclosed in curly braces {}.

Therefore, these contructs are not valid:

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{$b} => Not valid: vipermethod missing {buffer.set(year,2008); datetime.getdaysinyear($year)} => Not valid: semicolon not allowed here

To make them valid, enclose them in a vipermethod like sys.eval().

Example

An example that displays the number of days until new-year:

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{sys.eval( buffer.set(dt,datetime.now()); buffer.set(ny,convert.todate((datetime.getyear($dt)+1)+'-01-01')); math.floor(datetime.daysbetween($ny,$dt))+' days until new-year !' )}