Comment Expressions

Comment expressions are a special kind of comment retained for backward compatibility. Unlike ordinary comments, they are executable. Their format is:

#>exp(attr1: value1, attr2: value2, ...)

Here, exp is the expression type. The parentheses contain optional attributes. Many comment expressions must be followed by #>pop to end their scope, which runs from the line where the expression appears to the next #>pop.

End #>pop

#>pop

Ends the scope of the previous comment expression.

Rotate #>rot

#>rot(angle, cx, cy)

• angle (required): angle in radians
• cx, cy (required): center x and y

Translate #>tr

#>tr(dx, dy)

• dx (optional, default 0): horizontal offset
• dy (optional, default 0): vertical offset

Alpha #>alpha

#>alpha(a)

• a (optional, default 0): opacity in [0,1]; 0 transparent, 1 opaque

Matrix #>mat

#>mat(x00, x01, ..., x33)

4×4 matrix entries (default 0). Used for scale, translate, rotate, etc.

Conditional #>if etc.

#>if(condition)
#>elif(condition)
#>else
#>fi

• condition: any expression; 0 is false, non-zero is true. Use #>fi to end, not #>pop.

Legacy compatibility #>if-no-v2

#>if-no-v2

If your UML uses features not in V2, wrap content in this so older clients can be prompted to upgrade. In V1, comment expressions are ignored; #if-no-v2 effectively ignores its block.