Stop being overly dogmatic, it ALSO leads to worse code.
For example, search for "PROCEDURE Scan" here: https://people.inf.ethz.ch/wirth/ProjectOberon/Sources/Texts...
Control structures are deeply nested and this goes on for 64 (very dense) lines. The low line count but is an artifact of how Oberon is conventionally formatted. When reformatted to mimic the conventions of languages like C, Java or Python it works out to more than 120 lines.
When I program in Oberon (recreationally) I tend to follow this style even though I would extract the same code into a separate method were I writing in Java.
It means the compiler knows how much memory the function's activation frame will take and the offset into that for every variable before it encounters any code in the function.
Basically, it makes it easier to write a single-pass compiler. That was important in the 70s but is less important these days.
Does Titania not have/intend to have lexically local subscopes? That would seem very un-Wirthian to me.
I always thought there must be a better solution, like emitting the compiled function body first which just increments the offset whenever a space for a variable is required and emit the function entry after the function exit last, so you can set up the stack frame with full knowledge of it's use. Then the entry can jump to the body. Scoping to blocks would let you decrement the offset upon exiting the block which would result in less stack use which would almost always be more beneficial than the cost of the additional jump.
But this is not meant to be a fully fledged language, it's meant to be a teaching tool. If you want a fully fledged language that allows for out of order declarations, try Odin!
Also, the syntax of Oberon/Pascal doesn't really allow for it in a nice way. It kind of looks really weird when you allow for it out of order.
Variables are at the top because:
- you immediately see them (so, perhaps, easier to reason about a function? I dunno)
- the compiler is significantly simplified (all of Wirths' languages compile superfast and, if I'm not mistaken, all are single-pass compilers)
However, I feel that Wirth was overly dogmatic on his approaches. And "variables must always be at the top" is one of those.
Hint: This about this from a single pass compiler basis and how much memory needs to be reserved from the procedure's stack frame.
Are you sure you actually read my second bullet point?
If you read texts and papers by Wirth you'll see a single theme emerge: simplicity. Everything he didn't consider simple was thrown away and derided.
Unfortunately he got kinda stuck in that, and you can see it in all the Oberon flavors: he was clearly fighting against the limitations he imposed, but couldn't break out if them.
This made me smile; going to use it in the future.
I'm not sure of the value of seeing all of the variables used listed in one place, it has certainly led to me encountering a identifier scrolling up to determine the type then scrolling back down. When the variable is only used on a few consecutive lines it's just adding work to read and adding work to create. I daresay I have written harder to read code than I intended because I didn't want to go up and declare another variable for short term use. The temptation to inline the expression is always there, because you know what all the parts mean when you write it. It's only when you come back later that you get the regret.
It's possible it could be mitigated by defining something like (not sure if this is a valid grammar)
and bring in scoping on statement sequences. maybe call it stmt_block so that stmt_sequence can be a component that really is just a sequence of statements.