> can create purely syntactic obstacles to introducing important features, such like multi-line lambdas
The reason that python has problems with multi-line lambdas is that python lambdas are not like other python functions. The "body" of a python lambda is an expression while the body of other python functions is an indented statement block, with an implicit "return None" for fall through, requiring an explicit "return" for some other value.
Your lambdas could be like other functions. Or, horrors, you could define two forms, "anonymous" and "expression", where "expression" is like python lambdas and "anonymous" defines an anonymous function whose body is just like other function bodies (ie multi-line, requiring explicit "return" s).
The reason that python has problems with multi-line lambdas is that python lambdas are not like other python functions. The "body" of a python lambda is an expression while the body of other python functions is an indented statement block, with an implicit "return None" for fall through, requiring an explicit "return" for some other value.
Your lambdas could be like other functions. Or, horrors, you could define two forms, "anonymous" and "expression", where "expression" is like python lambdas and "anonymous" defines an anonymous function whose body is just like other function bodies (ie multi-line, requiring explicit "return" s).
do-while/until may pose bigger problems.