Hi Sven, Jason and Andrew wrote a string interpolation implementation for Andrew's language, Grace, in the parser. It works rather well and isn't too difficult to implement...
The equivalent would be to add it to RB Parser, and, security wise, it would be as vulnerable as calling Compiler evaluate: 'an unsafe string'. Regards, Thierry 2017-09-28 16:20 GMT+02:00 Sven Van Caekenberghe <[email protected]>: > Hi, > > I got into a little office discussion about string interpolation as it is > done in different programming languages. > > In Pharo we have String>>#format: which is pretty nice. It works as > follows: > > | x y | > x := 123. > y := #foo. > 'x={1} and y={2}' format: { x. y }. > > It is also possible to use a dictionary with keys, like this: > > | x y | > x := 123. > y := #foo. > 'x={x} and y={y}' format: { #x->x. #y->y } asDictionary. > > But this is not true string interpolation as described in [ > https://en.wikipedia.org/wiki/String_interpolation ]. The idea is to > write the value generating expressions directly inside the strings. > > Since in Pharo we add features not by extending the syntax but by adding > messages I wondered if it could be done for string interpolation. The goal > is to make the following work: > > | x y | > x := 123. > y := #foo. > 'It seems x equals {x} and y equals {y} while Pi is still {Float pi}' > interpolate. > > => 'It seems x equals 123 and y equals foo while Pi is still > 3.141592653589793' > > Here is the implementation I came up with: > > String>>#interpolate > "Format the receiver by interpolating the evaluation of expressions > in between curly brackets in the context of the sender as in the > following 3 oneline examples. > 'Today is {Date today}' interpolate. > | x | x := 123. 'x equals {x} and pi equals {Float pi}' interpolate. > 'In {#strings} you can escape \{ by prefixing it with \\' interpolate." > > | senderContext | > senderContext := thisContext sender. > ^ self class new: self size streamContents: [ :out | | stream | > stream := self readStream. > [ stream atEnd ] whileFalse: [ | currentChar | > (currentChar := stream next) == ${ > ifTrue: [ | expression result | > expression := stream upTo: $}. > result := Compiler new > evaluate: expression in: senderContext to: nil notifying: > nil ifFail: [ ^ nil ] logged: false. > out nextPutAll: result asString ] > ifFalse: [ > currentChar == $\ > ifTrue: [ stream atEnd ifFalse: [ out nextPut: stream next ] > ] > ifFalse: [ out nextPut: currentChar ] ] ] ] > > It is a hack that could certainly be improved. And there is of course an > obvious security problem. > > Thoughts ? > > Sven > > >
