Question

I’m trying to write a regular expression that will validate a variable assignments in a BB style code that I’m currently developing.

Variable assignments look like this

[assign {var_name} = "string value"]

You can assign to multiple variables like

[assign {var1} = {var2} = true]

Or add to a variable with

[assign {var_name} .= " more..."]

Increment/decrement variables

[assign {var}++] or [assign {var}--]

Assign a negated value

[assign {var1} = !{var2}]

So far I’ve come up with the following regex with doesn’t work very well

     /
       \[assign
         (?:
           [\s]*(?:
             [\!]?\{[^\}]+\}(?:(?:\+\+)|(?:\-\-))?
             |
             [0-9]+
             |
             \"[^\"]+\"
             |
             \'[^\']+\'
             |
             true
             |
             false
           )[\s]*(?:\=[\s]*|\.\=[\s]*)?
         )+
       \]
     /

I’m stuck with the following:

• I need to ensure that .= or = is used between each part
• And ensure that values and variables are assigned to variables, but not variables assigned to values
• Finally ensure there is an actual assignment unless the value is incremented or decremented

Update:
working regex

       \[assign(?:\s)* 
         (
           \{[^\}]+\}
           (?:
             \+\+
             |
             --
             |
             (?:\s)*(?:\.)?=(?:\s)*
             (?:(?:!)?\{[^\}]+\}(?:\s)*(?:\.)?=(?:\s)*)*
             (?:
               [0-9]+
               |
               "[^"]+"
               |
               '[^']+'
               |
               true
               |
               false
               |
               (?:!)?\{[^\}]+\}
             )
           )
         )
       (?:\s)*\]

Answer 1

If you only need to match those cases, you could use the following regular expression to parse them:

^(?:assign {var.*?})(\+\+|--| (?:\.)?= ({var.*?} = )*(true|".+"|!{var.*?}))$

It will match the following:

assign {var_name} = "string value"
assign {var1} = {var2} = true
assign {var_name} .= " more..."
assign {var}++
assign {var}--
assign {var1} = !{var2}
assign {var235} = "two"
assign {var1} = {var2} = {var3} = true

And it will not match the following:

assign lol = hi
assign {var3} = {var4}
assign {var5} = !"hi"