Johan,
There's nothing wrong with the function or Poly/ML or SML/NJ's
implementation. I think the difficulty you are having has to do with
differences in way Poly/ML and SML/NJ handle their read-eval-print loops
and the interaction between this and TextIO. From your previous message
to me it was clear that you are running this interactively. If you type
askName();
followed by a carriage return to Poly/ML the read-eval-print loop reads
up to and including the semicolon, leaving the newline introduced by the
carriage return in the buffer. Your call to TextIO.inputLine then reads
this. The next line you type then goes to Poly/ML.
A quick experiment with SML/NJ shows that it does things slightly
differently. It seems to read the whole line into its own buffer and
then compile parts of it. You can see the difference with
Poly/ML
> askName(); fred;
val it = SOME " fred;": string option
joe;
Error-Value or constructor (joe) has not been declared Found near joe
Static Errors
SML/NJ
- askName(); fred;
joe;
val it = SOME "joe;" : string option
stdIn:12.12-12.16 Error: unbound variable or constructor: fred
The handling of the read-eval-print loop is not standardised so
different compilers can perfectly legitimately implement this
differently. If you have two programs both reading the same stream you
need to be clear on exactly what they are doing.
David
Johan wrote:
Hello,
I am trying to learn SML, but drowning in its streams.
The following function does what I want in SML/NJ, but not in PolySML.
Is the function wrong, but SML/NJ lenient and PolySML not?
If the function is wrong, what is the best way to get
input from stdin without a newline?
fun askName () =
let
val a = TextIO.inputLine TextIO.stdIn
val b = String.translate (fn x => case x of #"\n" => ""|_ => str(x))
in
case a of
SOME("\n") => NONE
| SOME(s) => SOME (b s)
| NONE => NONE
end
Thanks
Johan
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