[jboss-jira] [JBoss JIRA] (DROOLS-4812) DMN FEEL warn if en-dash is present as a character in expression

[Matteo Mortari (Jira)]

Matteo Mortari created DROOLS-4812:
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             Summary: DMN FEEL warn if en-dash is present as a character in expression
                 Key: DROOLS-4812
                 URL: https://issues.jboss.org/browse/DROOLS-4812
             Project: Drools
          Issue Type: Enhancement
          Components: dmn engine
            Reporter: Matteo Mortari
            Assignee: Matteo Mortari


This is taken from the DMN spec :

{code:java}
(amount *rate/12) / (1 – (1 + rate/12)**-term)
{code}


however this would fail to parse correctly as the first subtraction sign is an "en-dash" (0x2013) and not a minus/hyphen sign (0x2D)

{code:java}
(amount *rate/12) / (1 – (1 + rate/12)**-term)
                       ^ 
(amount *rate/12) / (1 - (1 + rate/12)**-term)
{code}

while an "em-dash" is much more noticeable, this "en-dash" can be confused more easily, especially depending on the font used:
 {code:java}
– en-dash                     
- minus, or hyphen (standard)
— em-dash (much more noticeable in the difference)
{code}

It is suggested for the parser/compile to emit a warning if the en-dash is used in an expression --or potentially if it's the last character in a viable alternative.

A good way to check for the behavior is to use the wrong expression above to exhibit the behavior when the en-dash is misplaced for a minus sign for a subtraction operation.



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