Substituting 4GL variables for constants

You may want your expression to depend on a data variable rather than on the constant string, such as "HELLO".

For this, we use RTL expressions embedded in curly braces.

Note: We are now mixing two languages. The content within the braces is RTL, the content outside the braces is a PXML expression.

The rules for embedding RTL in PXML are:

wherever a numeric constant is allowed in PXML, you can insert an RTL numeric expression (enclosed in curly braces) instead.
wherever a string constant is allowed in PXML, you can insert a RTL string expression (enclosed in curly braces) instead.

For example, consider this expression:

max(10cm,width("HELLO"))

This PXML expression contains one numeric constant ("10") and one string constant ("HELLO"). These constants can be replaced by data variables, enclosed in curly braces:

max({order_line.titlewidth}cm,width({order_line.title}))

For this expression to be legal, the variable order_line.titlewidth has to be of type Numeric, and the variable order_line.title has to be of type String.

Note: You cannot construct a dynamic expression where the function names (such as max or width) or the unit names (such as cm) are dynamic.