This solution will not work for environments without sources too where names like t1, t2 are used for temporary variables. Anyway, nice idea.
-- Pavel Dne čtvrtek 28. září 2017 Sven Van Caekenberghe <[email protected]> napsal(a): > 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 > > >
