Implement the where: and do: to have the result stated at the end (Issue #863)

[ad4mf06]

Changes

• Added block_where_stmt grammar rule supporting lhs = where: <suite> syntax
• Last statement in the suite becomes the result assigned to lhs
• Supports both where: and do: keywords
• Handles variable scoping with name management

Example

out = where:
    x = 1 + 2 + 3
    y = 4 + 5 + 6
    x + y
assert out == 21

Testing

Added comprehensive tests in coconut/tests/src/cocotest/agnostic/primary_1.coco covering:

• Addition: Simple sum operations
• Multiplication: Product calculations
• Division: Division operations
• Chained calculations: Variables depending on previous computations
• String concatenation: Text operations
• Large blocks: Multiple statements with complex expressions

All tests are duplicated to verify both where: and do: syntax work identically.

Fixes #863

[evhub]

This looks pretty good! We should pick only one of these two syntaxes, though, and you should make sure to test that the variables in the where clause are properly hidden from the enclosing scope. I think I probably prefer the where: syntax over the do: syntax since do has a specific meaning in many functional programming languages that is not this.

[ad4mf06]

I agree with you, "where" is a better name for this function. I'll remove the do: syntax and remove the test I added with that syntax. I also added a test to make sure that the variables in the where clause are properly hidden from the enclosing scope.