Comment by Zambyte

6 days ago

If takes two or three arguments, but never one. The condition is the one made syntactically obvious in most languages, the consequent is another required argument, and the alternative is optional.

10 comments

Zambyte

dylan604 6 days ago

Huh? if (true) {} takes precisely one argument.

mjburgess 6 days ago
That's an application of `if` with one of the arguments empty.
The semantics of `if` requrie at least, `if(cond, clause)`, though more generally, `if(cond, clause, else-clause)`
- devnullbrain 6 days ago
  
  You and Zambyte are both doing the same thing the top level comment is complaining about.
  e.g. in C:
  https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3220.pdf
  (6.8.5.1) selection-statement: if ( expression ) secondary-block if ( expression ) secondary-block else secondary-block
  in C++:
  https://eel.is/c++draft/gram.stmt
  selection-statement: if constexpropt ( init-statementopt condition ) statement if constexpropt ( init-statementopt condition ) statement else statement if !opt consteval compound-statement if !opt consteval compound-statement else statement
  where
  condition: expression attribute-specifier-seqopt decl-specifier-seq declarator brace-or-equal-initializer structured-binding-declaration initializer
  More examples:
  https://docs.python.org/3/reference/grammar.html
  https://doc.rust-lang.org/reference/expressions/if-expr.html...
  https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...
  expression != argument
  
  5 replies →
andriamanitra 5 days ago

Depends on the language! If "if" wasn't a keyword, in Ruby that would be calling a method that takes one positional argument and one block argument, such as `def if(cond, &body) = cond && body.call`. In PureScript that could be a call to a function with signature `if :: Boolean -> Record () -> _`.
But I assume the comment you were replying to was not referring to the conditional syntax from C-like languages, instead referring to a concept of an if "function", like the `ifelse` function in Julia [1] or the `if` form in Lisps (which shares the syntax of a function/macro call but is actually a special form) [2], neither of which would make sense as one argument function.
[1] https://docs.julialang.org/en/v1/base/base/#Base.ifelse
[2] https://www.gnu.org/software/emacs/manual/html_node/elisp/Co...
Zambyte 4 days ago
I count two: true and void. This becomes obvious in languages that have consistent application syntax like Lisp, which would write this as
(if true '())
Or if you wanted to capture the exact same semantics (rather than returning a null value to the continuation of the if)
(if true (values))
Now it's obvious that if takes two (or three) arguments :)