a if c else b // basic case

a if c else b if d else e // is ambiguous
(a if c else b) if d else e // case 1
a if c else (b if d else e) // case 2 (Python's semantics)


case 1 is implemented by:

expr ::= or_expr [ IF expr ELSE or_expr ]*
or_expr ::= and_expr [ OR or_expr ]

case 2 is implemented by:

expr ::= (and_expr OR expr | and_expr) [ IF expr ELSE expr ]

-----------

instructions:

<conditional>
jumpifnot label1
<expr1>
jump label2
label1:
<expr2>
label2: