If you want to do numeric operations with numbers, that are considered a string, then you need to explicit tell XPath, that a value is numeric with the function number(). That is e.g. the case, if you want to extract data from an input spooled file and use that in a numeric calculation.

This XPath expression e.g. fails in the designer (even though positions 57-60 in line 13 in the sample spooled file is 1004):

ng:spoolMap(//page[1], 57, 60, 13, 13)+100

It fails with the error message: Cannot evaluate string+integer.

The solution is to convert the string from the spooled file into numeric like so:

number(ng:spoolMap(//page[1], 57, 60, 13, 13))+100

You can also do normal calculations as adding, subtracting, multiplicating, dividing in XPath. This can e.g. also be stated as an XPath expression:

substring(/Data/Header/Type, 4,3)*5 div 6

 (you need blanks around ‘div’)

With the value (‘VDA4902') as mentioned above (for /Data/Header/Type)  this will be calculated as 490 multiplied with 5 (equal 2450) divided by 6 making the result: ‘408.3333333333333'.

So as you can see divide is stated as ‘div’ and modulo is ‘mod’.

A numeric result is converted to a string when returning the value so you can e.g. combine substring functions to the result, so we can even limit the number above to 2 decimals in this manner:

concat(substring-before(substring(/Data/Header/Type, 4,3)*5 div 6,'.') ,'.',substring(substring-after(substring(/Data/Header/Type, 4,3)*5 div 6,'.'),1,2))

Numbers must be written with a dot as decimal point without any thousand separator. To convert a decimal comma into a dot and to remove any dots (used as 1000 delimiter) you can use the translate function like this: translate(string,”,.”,”.”). Assuming you are using a dot as a decimal point and a comma as thousand separator you can remove the commas with this expression: translate(string,”,”,”“).

The result can then be used in numeric expressions.

The explaination of the above is, that we concatenate the substrings consisting of:

1. The part of the amount, that is in front of the ‘.’ i.e. ‘408' in this case.
   
2. The ‘.’.
   

3. Only the 2 first characters of the part of the amount, that is after the ‘.’ i.e. ‘33' in this case.

   - making the final result: ‘408.33'.

A more simple round of can also be done if you set the data type (in the text element) to numeric and then use this formula:

round(100*(/Data/Header/Type*5 div 6)) div 100

The round() function will round off to the nearest integer. round(1.234) outputs 1 and round(0.5) also outputs 1.

The standard format-number Xpath function has these parameters:

format-number(number ,pattern [,decimal-format] )

number

The number to format. The number must be in the correct format i.e. no thousand separator and the optional decimal point must be dot. You can use the translate() function to remove or replace specific characters.

pattern

The pattern of the number. You can use these options:

decimal-format (optional)

This is not covered in this manual. Refer to standard XPath descriptions for full details.

Examples of the format-number.

The specifications on the left results in the output on the right:

The boolean function returns a boolean i.e. either true() or false() depending on the argument. In InterFormNG2 it can e.g. be used for verifying if a nodeset is empty e.g. before using the same nodeset in a Repeat element.

If the nodeset /abc/node is empty, then this expression returns false():

boolean(/abc/node)

and true() if the nodeset exists.

An example of where is useful is included in the section "Iteration & Grouping" -> "Avoiding warnings in job logs when repeats select no nodes".