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Add basic string interpolation / string templates (#743)
Fixes #722 and adds basic support for string templates. There are a few caveats to keep in mind with the current initial implementation: - All arguments already have to be strings. It is basically just syntactic sugar so that you can write `"${a.show} and ${b.show}"` instead of `a.show ++ " and " ++ b.show` where `a` and `b` are some 'showable' values. Internally, however, this is just how it is desugared. - String templates cannot be used to match string literals in pattern matches - The generated JS code looks a bit weird: ``` const v_r_897 = $effekt.println(((((((((("GET ") + (domain_0)))) + (((("/users/") + (user_0))))))) + (((("/resource/") + (('' + resourceId_0)))))))); ``` + If one forgets to call `show` on arguments which are not already of type string, the error messages are hideous and possibly confusing: <details> <summary>error</summary> ``` -There are multiple overloads, which all fail to check: -Possible overload: effekt::println of type Bool => Unit - Expected String but got Int. - Expected Bool but got String. - -Possible overload: list::println of type List[Bool] => Unit - Expected String but got Int. - Expected List[Bool] but got String. - -Possible overload: array::println of type Array[Int] => Unit - Expected String but got Int. - Expected Array[Int] but got String. - -Possible overload: effekt::println of type String => Unit - Expected String but got Int. - -Possible overload: list::println of type List[Int] => Unit - Expected String but got Int. - Expected List[Int] but got String. - -Possible overload: effekt::println of type Byte => Unit - Expected String but got Int. - Expected Byte but got String. - -Possible overload: list::println of type List[String] => Unit - Expected String but got Int. - Expected List[String] but got String. - -Possible overload: list::println of type List[Double] => Unit - Expected String but got Int. - Expected List[Double] but got String. - -Possible overload: array::println of type Array[String] => Unit - Expected String but got Int. - Expected Array[String] but got String. - -Possible overload: effekt::println of type Ordering => Unit - Expected String but got Int. - Expected Ordering but got String. - -Possible overload: array::println of type Array[Bool] => Unit - Expected String but got Int. - Expected Array[Bool] but got String. - -Possible overload: effekt::println of type Unit => Unit - Expected String but got Int. - Expected Unit but got String. - -Possible overload: option::println of type Option[Int] => Unit - Expected String but got Int. - Expected Option[Int] but got String. - -Possible overload: option::println of type Option[Double] => Unit - Expected String but got Int. - Expected Option[Double] but got String. - -Possible overload: array::println of type Array[Double] => Unit - Expected String but got Int. - Expected Array[Double] but got String. - -Possible overload: effekt::println of type Double => Unit - Expected String but got Int. - Expected Double but got String. - -Possible overload: effekt::println of type Int => Unit - Expected String but got Int. - Expected Int but got String. - -Possible overload: option::println of type Option[Bool] => Unit - Expected String but got Int. - Expected Option[Bool] but got String. - - println("GET ${domain}/users/${user}/resource/${resourceId}") ``` </details> Apart from that, the changes are really lightweight because of the early desugaring in the parser. I am looking forward to your feedback and ideas. --------- Co-authored-by: Jiří Beneš <mail@jiribenes.com> Co-authored-by: Marvin <git@marvinborner.de> Co-authored-by: Philipp Schuster <philipp.schuster@uni-tuebingen.de> Co-authored-by: Jonathan Brachthäuser <jonathan@b-studios.de>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,2 @@ | ||
| GET https://api.effekt-lang.org/users/effekt/resource/42 | ||
| Fix point combinator: \ f -> (\ x -> f x x) \ x -> f x x |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,39 @@ | ||
| import stringbuffer | ||
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| type Expr { | ||
| Var(id: String) | ||
| Abs(param: String, body: Expr) | ||
| App(fn: Expr, arg: Expr) | ||
| } | ||
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| def pretty { prog: () => Unit / {literal, splice[Expr]} }: String = { | ||
| with stringBuffer | ||
| try { | ||
| prog() | ||
| do flush() | ||
| } with literal { s => | ||
| resume(do write(s)) | ||
| } with splice[Expr] { expr => | ||
| expr match { | ||
| case Var(id) => | ||
| do write(id) | ||
| case App(Abs(param, body), arg) => | ||
| do write(pretty"(${Abs(param, body)}) ${arg}") | ||
| case App(fn, arg) => | ||
| do write(pretty"${fn} ${arg}") | ||
| case Abs(param, body) => | ||
| do write(s"\\ ${param} -> " ++ pretty"${body}") | ||
| } | ||
| resume(()) | ||
| } | ||
| } | ||
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| def main() = { | ||
| val domain = "https://api.effekt-lang.org" | ||
| val user = "effekt" | ||
| val resourceId = 42 | ||
| println("GET ${domain}/users/${user}/resource/${resourceId.show}") | ||
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| val fixpoint = Abs("f", App(Abs("x", App(Var("f"), App(Var("x"), Var("x")))), Abs("x", App(Var("f"), App(Var("x"), Var("x")))))) | ||
| println(pretty"Fix point combinator: ${fixpoint}") | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,4 +1,5 @@ | ||
| import map | ||
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| import bytearray | ||
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| def counter(words: List[String]): Map[String, Int] = { | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,4 +1,5 @@ | ||
| import set | ||
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| import bytearray | ||
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| def unique(words: List[String]): Set[String] = { | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,65 @@ | ||
| module stringbuffer | ||
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| import bytearray | ||
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| interface StringBuffer { | ||
| def write(str: String): Unit | ||
| def flush(): String | ||
| } | ||
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| def stringBuffer[A] { prog: => A / StringBuffer }: A = { | ||
| val initialCapacity = 128 | ||
| var buffer = bytearray::allocate(initialCapacity) | ||
| // next free index to write to | ||
| var pos = 0 | ||
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| def ensureCapacity(sizeToAdd: Int): Unit = { | ||
| val cap = buffer.size - pos + 1 | ||
| if (sizeToAdd <= cap) () | ||
| else { | ||
| // Double the capacity while ensuring the required capacity | ||
| val newSize = max(buffer.size * 2, buffer.size + sizeToAdd) | ||
| buffer = buffer.resize(newSize) | ||
| } | ||
| } | ||
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| try { prog() } | ||
| with StringBuffer { | ||
| def write(str) = { | ||
| val bytes = fromString(str) | ||
| ensureCapacity(bytes.size) | ||
| bytes.foreach { b => | ||
| buffer.unsafeSet(pos, b) | ||
| pos = pos + 1 | ||
| } | ||
| resume(()) | ||
| } | ||
| def flush() = { | ||
| // resize buffer to strip trailing zeros that otherwise would be converted into 0x00 characters | ||
| val str = bytearray::resize(buffer, pos).toString() | ||
| // after flushing, the stringbuffer should be empty again | ||
| buffer = bytearray::allocate(initialCapacity) | ||
| resume(str) | ||
| } | ||
| } | ||
| } | ||
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| /// Handler for string interpolation using a string buffer | ||
| def s { prog: () => Unit / { literal, splice[String] } }: String = | ||
| stringBuffer { | ||
| try { prog(); do flush() } | ||
| with splice[String] { x => resume(do write(x)) } | ||
| with literal { s => resume(do write(s)) } | ||
| } | ||
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| namespace examples { | ||
| def main() = { | ||
| with stringBuffer | ||
| do write("hello") | ||
| do write(", world") | ||
| // prints `hello, world` | ||
| println(do flush()) | ||
| // prints the empty string | ||
| println(do flush()) | ||
| } | ||
| } |