Why SELECT not respond on string variable?

[Aurel]

Hio Charles
sorry but i must bothering you about this problem.
sorry again if is fixed in new version...blame on me 
i just try in one example :

string func
float res,result
    select func
       case "SIN" : result =sin(res)
       case ....
       case ....
   end select
 so in this case SELECT not respond on string varible func
BUT if i use

  if func = "SIN"   ....... then work
i just hope that this would be fixed
or i will (must ) replace func  with integer
like fun

int fun

 select fun

once again if this is solved in last version
all best Aurel 
     

[Charles Pegge]

Hi Aurel,

Like C. the oxygen case is a low-level construct that does not support string comparisons. Cases translate directly into assembler. So you will have to use if..elseif..endif

[JRS]

So you will have to use if..elseif..endif

Script BASIC doesn't have a SELECT/CASE which I find restrictive in most BASIC languages. I've created some fairly large IF/ELSE IF/ELSE/END IF structures  with complex expressions I could never do with a common CASE.

[Charles Pegge]

Case blocks are very fast in compiled languages. You can still use them for filtering:

Code: [Select]

string func
float res,result
   select asc func
       case "S"
         if func="SIN" then
           result =sin(res)
         elseif func="SQR" then
           result =sqr(res)
         end if
         ...
       case "T"
       case ....
   end select


[Aurel]

Case blocks are very fast in compiled languages

Yes Charles ..and that is why I ask
thanks for suggestion...
my next idea would be ..maybe i can use string pointer casting ?

[Aurel]

I expected that method with string pointer casting work
but not exactly because no mather what is s, only first case is selected
 


here is one way:

Code: [Select]

'string casting -> select/filtering

string s="SIN"
'(p AS string pointer)
p = cast (string)s

select p
case strptr "SIN"
print "OK..func(SIN)"
case strptr "TAN"
print "OK..func(TAN)"
end select

Ok it seems that best option would be to have strings
signed with numbers then use SELECT
like
fun_sin = 1
fun_cos = 2
fun_tan=3
then select
      select fun
            case 1
                 print fun_sin: sin(res)
Ok i will see.... 

[Charles Pegge]

If you convert your 3 or 4 character keywords into integers, you can use them in a case block like this:

int*p=strptr func

Code: [Select]

'THIS WILL WORK FOR 3 OR 4 CHAR KEYWORDS
string func="SQR"
float res=2, result
int*p=strptr func
   select p
       case "SIN" : result=sin(res)
       case "SQR" : result=sqr(res)
   end select

   print result '1.41...


[Aurel]

Hi Charles
I forgot for this way 
that is great and i tested more than 3-4 chars ..18 chars
and WORK ! 

Code: [Select]

'THIS WILL WORK FOR 3 OR 4 CHAR KEYWORDS
string func
func="OxygenBasicSqrRoot"
'func="SIN"
float res=2, result
int *p = strptr func
   select p
       case "SIN"
result=sin(res)
       case "OxygenBasicSqrRoot"
          result=sqr(res)
       case else
          print "unknown func?"
   end select

   print result '1.41...

.

[Charles Pegge]

Careful! Only the first 4 characters are tested, as an integer

[Aurel]

Charles
May i ask why CAST not work as *p = strptr s ?
and what is a main difference...
this thematic is not explained  well and can be used in many string processing programs ,right?

[Aurel]

Charles
I just tried with Djpeter ( from FB forum) math solver
and seems that your method work fine 

you may try :

Code: [Select]

' simple expression solver FB DJPeters
'Oxygen basic version by Aurel
declare sub Unary        (byref Result as float)
declare sub Parenthesized(byref Result as float)
declare sub Exponent     (byref Result as float)
declare sub MulDiv       (byref Result as float)
declare sub AddSub       (byref result as float)
'declare sub DoUnary      (Op as string,byref Result as double)
declare sub GetToken()
declare function IsDigit() as int
declare function IsAlpha() as int
declare function IsWhite() as int
declare function IsDelimiter() as int
declare function isFunction() as int

'enum TokenTypes / integer constant
 % EOL = 1
 % DELIMETER = 2
 % NUMBER = 3
 % IDENT = 4
'end enum

string  Expression,Token,ch
int TokenType,cPos,TRUE=1,FALSE=0

sub sError(sErr as string)
  print "Error: " & sErr
  'beep:sleep:end
end sub
'---------------------------------
function IsDigit() as int
  int c: c=asc(ch)
  if c>47  and c<58 or c=46
return TRUE
  end if
return FALSE
end function
'--------------------------------
function IsAlpha() as int
  int c: c=asc(ucase(ch))
  if c>64 and c<91
  return TRUE
  end if
  return FALSE
end function
'---------------------------------
function IsWhite() as int
  int c : c=asc(ch)
  return ((c=32) or (c=9))
end function
'---------------------------------
function IsDelimeter() as int
  int c: c=asc(ch)
  if c=9 then return TRUE
  c=instr("+-*/^()",ch)
  if c>0 then return TRUE
  return FALSE
end function
'---------------------------------------
function IsFunction() as int
int *f = strptr token
Select f
 case "SIN"   
       return TRUE
 case "COS"
       return TRUE
 case "TAN"
       return TRUE
 case "SQR"
       return TRUE
 end select
 
  return FALSE
end function
'----------------------------------------
sub GetChar
  cPos=cPos+1
  if cPos>len(Expression) then
    ch="":return
  end if
  ch = mid(Expression,cPos,1)
end sub
'---------------------------------------
sub GetToken()
  GetChar()
  if Ch="" then
    Token     = ""
    TokenType = EOL
    return
  end if

  if IsDelimeter()= TRUE then
    Token     = Ch
    TokenType = DELIMETER
    return
  end if

  if IsDigit()= TRUE then
    Token = ""
    while IsDelimeter()=FALSE and Ch<>""
      Token=Token+Ch
      GetChar()
    wend
    TokenType = NUMBER
    cPos=cPos-1
    return
  end if

  if IsAlpha() = TRUE then
    Token = ""
    while IsAlpha()=TRUE and Ch<>""
      Token = Token + Ch
      GetChar()
    wend
 'print "TOKEN:" & token
    Token= UCASE(Token)
    TokenType = IDENT
    cPos=cPos-1
    return
  end if
end sub
'---------------------------------------------

sub AddSub(byref Result as float)
  string Op
  float Temp
  Unary(result)
  Op=Token
  while Op = "+" or Op = "-"
    GetToken()
  Unary(Temp)
    if Op="+" then
      Result=Result+Temp
    end if
    if Op="-"
      Result=Result-Temp
    end if
    Op = Token
  wend
end sub

sub Unary(byref Result as float)
  string Op
  if TokenType=DELIMETER and (Token="+" or Token="-")
    Op = Token
    GetToken()
  end if
  MulDiv(Result)
  if Op="-" then Result = -Result
end sub

sub MulDiv(byref Result as float)
  string Op
  float Temp
  Exponent(Result)
  Op=Token
  while Op = "*" or Op = "/"
    GetToken()
    Exponent(Temp)
    if op="*" then
      Result *= Temp
    else
      if (Temp=0) then
        sError("division by zero")
      else
        Result = Result / Temp
      end if
    end if
    Op = Token
  wend
end sub

sub Exponent(byref Result as float)
  float Temp
  Parenthesized(Result)
  if (Token="^") then
    GetToken()
    Parenthesized(Temp)
    Result ^= Temp
  end if
end sub

sub Parenthesized(byref Result as float)
  if token = "-" or token = "+" then Unary(Result)
  if (Token ="(") and (TokenType = DELIMETER) then
    GetToken()
    AddSub(Result)
    if (Token <> ")") then serror("unbalanced round brackets")
    GetToken()
  else
    select TokenType
      case NUMBER
        Result = val(Token)
        GetToken()
      case IDENT
        if IsFunction()= TRUE then
          string Func : Func = Token
          int *p = strPtr Func
          float res : res = result
          GetToken()
          Parenthesized(res)

      select p
         ' case "ABS": result = abs(res)
         ' case "ATN": result = atn(res)
          case "COS": result = cos(res)
          'case "EXP": result = exp(res)
          'case "FIX": result = fix(res)
          'case "INT": result = int(res)
          'case "LOG": result = log(res)
          'case "SGN": result = sgn(res)
          case "SIN": result = sin(res)
          case "SQR": result = sqr(res)
          case "TAN": result = tan(res)
      end select
      else
        serror("unknow ident / function " & Token)
      end if
    end select
  end if
end sub

function Eval(byval s as string) as float
  float result
  Expression=s
  cPos=0
  GetToken()
  AddSub(result)
  return result
end function

string e
e = "sin(2+3)"
print e & " = " & Eval(e)


.

[Charles Pegge]

Hi Aurel,

Cast is just a way of fooling the compiler into accepting onions as apples