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This is what golang does. https://go.dev/doc/effective_go#semicolons https://go.dev/doc/effective_go#semicolons

by ilyagr 2y ago

xpl 2y ago
Also, JavaScript.
- gary_0 2y ago
  And Kotlin and Swift.
- xigoi 2y ago
  Except JavaScript does it wrong.
  - trealira 2y ago
    What makes Go's semicolon insertion algorithm different from JavaScript's? They seem similar to me. Isn't it just that the Go compiler requires very strict formatting, which saves you from getting bitten by errors due to unexpected semicolons?
    - xigoi 2y ago
      The following (contrived) JavaScript code does not work: let x = 5 (function() { console.log(x) })() The equivalent Go code works: package main import "fmt" func main() { x := 5 (func() { fmt.Printf("%d", x) })() }
      - trealira 2y ago
        Thanks, that's a good case. Actually, the JavaScript semicolon insertion algorithm [0] seems more complex than I had remembered. I had thought of them as variations on the semicolon insertion in BCPL, but it seems like that's an oversimplification. For reference, these are the BCPL rules: The canonical symbol SEMICOLON is inserted between pairs of items if they appeared on different lines and if the first was from the set of items which may end a command or definition, namely: BREAK RETURN FINISH REPEAT SKET RKET SECTKET NAME STRINGCONST NUMBER TRUE FALSE and the second is from the set of items which may start: a command, namely: TEST FOR IF UNLESS UNTIL WHILE GOTO RESULTIS CASE DEFAULT BREAK RETURN FINISH SECTBRA RBRA VALOF LV RV NAME ... ( ) [ ] § § are used to denote RBRA RKET SBRA SKET SECTBRA and SECTKET. [0]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Lexical_grammar#automatic_semicolon_insertion https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...
- kazinator 2y ago
  Bourne and POSIX shell: for x in *.txt; do echo $x; done for x in *.txt do echo $x done
trealira 2y ago
Haskell also inserts semicolons, but it has a different rule, which I think is a bit interesting. If the current line starts on the same line that the previous expression started on, then a semicolon is inserted at the beginning of the current line. There are also some messy rules about opening and closing braces being inserted. So, this: do expr1 expr2 do expr3 expr4 Ends up being parsed as though it were written like this: do { expr1 ; expr2 do { expr3 ; expr4 } } If the next line is indented, it's just taken as a continuation of the previous line's expression, so nothing needs to happen. [0]: https://amelia.how/posts/parsing-layout.html https://amelia.how/posts/parsing-layout.html

This is what golang does. https://go.dev/doc/effective_go#semicolons https://go.dev/doc/effective_go#semicolons

by ilyagr 2y ago

This is what golang does. https://go.dev/doc/effective_go#semicolons https://go.dev/doc/effective_go#semicolons

xpl 2y ago

Also, JavaScript.

gary_0 2y ago
And Kotlin and Swift.
xigoi 2y ago
Except JavaScript does it wrong.
- trealira 2y ago
  What makes Go's semicolon insertion algorithm different from JavaScript's? They seem similar to me. Isn't it just that the Go compiler requires very strict formatting, which saves you from getting bitten by errors due to unexpected semicolons?
  - xigoi 2y ago
    The following (contrived) JavaScript code does not work: let x = 5 (function() { console.log(x) })() The equivalent Go code works: package main import "fmt" func main() { x := 5 (func() { fmt.Printf("%d", x) })() }
    - trealira 2y ago
      Thanks, that's a good case. Actually, the JavaScript semicolon insertion algorithm [0] seems more complex than I had remembered. I had thought of them as variations on the semicolon insertion in BCPL, but it seems like that's an oversimplification. For reference, these are the BCPL rules: The canonical symbol SEMICOLON is inserted between pairs of items if they appeared on different lines and if the first was from the set of items which may end a command or definition, namely: BREAK RETURN FINISH REPEAT SKET RKET SECTKET NAME STRINGCONST NUMBER TRUE FALSE and the second is from the set of items which may start: a command, namely: TEST FOR IF UNLESS UNTIL WHILE GOTO RESULTIS CASE DEFAULT BREAK RETURN FINISH SECTBRA RBRA VALOF LV RV NAME ... ( ) [ ] § § are used to denote RBRA RKET SBRA SKET SECTBRA and SECTKET. [0]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Lexical_grammar#automatic_semicolon_insertion https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...
kazinator 2y ago
Bourne and POSIX shell: for x in *.txt; do echo $x; done for x in *.txt do echo $x done

trealira 2y ago

Haskell also inserts semicolons, but it has a different rule, which I think is a bit interesting. If the current line starts on the same line that the previous expression started on, then a semicolon is inserted at the beginning of the current line. There are also some messy rules about opening and closing braces being inserted. So, this: do expr1 expr2 do expr3 expr4 Ends up being parsed as though it were written like this: do { expr1 ; expr2 do { expr3 ; expr4 } } If the next line is indented, it's just taken as a continuation of the previous line's expression, so nothing needs to happen. [0]: https://amelia.how/posts/parsing-layout.html https://amelia.how/posts/parsing-layout.html