Editing Dangling else (section)

===Avoiding ambiguity by changing the syntax===
The problem can also be solved by making explicit the link between an else and its if, within the syntax. This usually helps avoid human errors.<ref>[https://code.google.com/archive/p/copute/issues/21#c2 Ambiguity of dangling else: non-context-free grammars are semantically opaque]</ref>

Possible solutions are:
* Having an "end if" symbol delimiting the end of the if construct. Examples of such languages are [[ALGOL 68]], [[Ada (programming language)|Ada]], [[Eiffel (programming language)|Eiffel]], [[PL/SQL]], [[Visual Basic]], [[Modula-2]], and [[AppleScript]].
* Disallowing the statement following a "then" to be an "if" itself (it may however be a pair of statement brackets containing only an if-then-clause). Some implementations of [[ALGOL 60]] follow this approach.<ref>''4.5.1 Conditional Statements — Syntax'' in P. Nauer (ed.), ''Revised Report on the Algorithmic Language ALGOL 60'', CACM 6,1, 1963 pp. 1-17</ref>
* Requiring braces (parentheses) when an "else" follows an "if".<ref>[https://code.google.com/archive/p/copute/issues/21#c1 Ambiguity of dangling else: require braces when else follows if]</ref>
* Requiring every "if" to be paired with an "else". To avoid a similar problem concerning semantics rather than syntax, [[Racket (programming language)|Racket]] deviates from [[Scheme (programming language)|Scheme]] by considering an <code>if</code> without a fallback clause to be an error, effectively distinguishing conditional ''expressions'' (i.e <code>if</code>) from conditional ''statements'' (i.e <code>when</code> and <code>unless</code>, which do not have fallback clauses).
* Using different keywords for the one-alternative and two-alternative "if" statements. [[S-algol]] uses <code>if e do s</code> for the one-alternative case and <code>if e1 then e2 else e3</code> for the general case.<ref>{{citation |last=Davie |first=Antony J. T. |author2=Ronald Morrison |editor=Brian Meek |title=Recursive Descent Compiling |series=Ellis Horwood series in computers and their applications |year=1981 |publisher=Ellis Horwood |location=Chichester, West Sussex |isbn=0-470-27270-8 |page=20}}</ref>
* Requiring braces unconditionally, like [[Swift (programming language)|Swift]] and [[Rust (programming language)|Rust]]. This is effectively true in [[Python (programming language)|Python]] as its indentation rules delimit every block, not just those in "if" statements.