In article <slr### [at] fwicom> , Ron Parker 
<ron### [at] povrayorg>  wrote:

>> Given L is a list,
>> who could tell "every i:=1 to *L/2 do L[i]:=:L[-i]" reverses it?
>
> Hm, that would work in Perl, too, with very few modifications.
>
> Of course, @L = reverse @L would work, too...

I picked a short example.  Below is a scanner, also given as *educational*
example (from http://www.iit.edu/~tc/), in particular note sequences like
"||:= =", or the operators for connecting strings, because that is what the
"++" does.  Now guess what the "?" does!

Basically all operators are unqiue for each data type, which gives you a farm
of operators.  In order to implement those you end up with other interesting
character sequences like "~==="...

    Thorsten


procedure scan()
local t,c,b
static whiteSpace,initIdChars,idChars,hexdigits,commentDepth,commentLineNo
initial {
 /inputFile := &input
 inputLineNumber := 1
 inputColumn := 1
 inputLine := read(inputFile)
 eoiToken := &null
 whiteSpace := &ascii[1:34] #control ++ blank
 initIdChars := &letters
 hexdigits := &digits ++ 'ABCDEF'
 idChars := &letters ++ &digits ++ '$_'
 keywordSet := set([
  "DEF","VAL","while","bu"
 ])
}
if \eoiToken then return eoiToken
repeat inputLine ? {
 tab(inputColumn)
 tab(many(whiteSpace))
 c := &pos
 if b := (tab(any('+-'))|"") ||
   tab(many(&digits)) then {
  if b := b || fractionPart() ||
      scaleFactor() then {
   t := Token("signedFloat",b,
    inputLineNumber,c)
  } else if b ||:= fractionPart() then {
   t := Token("signedFloat",b,
    inputLineNumber,c)
  } else if b ||:= ="." || scaleFactor() then {
   t := Token("signedFloat",b,
    inputLineNumber,c)
  } else {
   t := Token("signedInt",b,
    inputLineNumber,c)
  }
  inputColumn := &pos
  return t
 } else
  if any(initIdChars) then {
  t := Token("ident",tab(many(idChars)),
   inputLineNumber,c)
  inputColumn := &pos
  if member(keywordSet,t.body) then
   t.type := t.body
  return t
 } else
  if b := =("~=" | ">=" | "<=" | "->") then {
  inputColumn := &pos
  return Token(b,b,inputLineNumber,c)
 } else
  if ="(*" then {
  inputColumn := &pos
  commentDepth := 1
  commentLineNo := inputLineNumber
  while commentDepth > 0 do {
   tab(upto('*(')|0)
   if pos(0) then {
       &pos := 1
       inputLineNumber +:= 1
       if not (&subject :=
     inputLine := read(inputFile))
       then {
    eoiToken := Token("EOI","EOI",
     inputLineNumber,1)
    write("end of input in comment beginning at ",
     commentLineNo)
    return eoiToken
       }
    } else if ="*)" then {
     commentDepth -:= 1
    } else if ="(*" then {
     commentDepth +:= 1
    } else {
     move(1)
    }
  }
  inputColumn := &pos
 } else
  if b := tab(any('\',=()[]<>+-*/@;:.')) then {
  inputColumn := &pos
  return Token(b,b,inputLineNumber,c)
 } else
  if pos(0) then {
  inputColumn := 1
  inputLineNumber +:= 1
  if not (inputLine := read(inputFile)) then {
   eoiToken := Token("EOI","EOI",
     inputLineNumber,1)

   return eoiToken
  }
 } else
  if ="\"" then {
  b := tab(find("\""))
  if not( = "\"" ) then {
   write("unterminated string at ",
    inputLineNumber," ",c)
  }
  t := Token("string",b,inputLineNumber,c)
  inputColumn := &pos
  return t
 } else
  {
  write("unexpected character: ",move(1),
   " at line ",inputLineNumber," column ",c)
  inputColumn := &pos
 }
}
end

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