isNumber()

[bluatigro]

test this please

and/or report mistakes






end
function isNumber( x$ )
 nr$ ="-0123456789e."
 x$ = lower$( x$ )
 fl = 1
 for i = 0 to 255
   if not( instr( nr$ , chr$( i ) ) ) then
     if instr( x$ , chr$( i ) ) then fl = 0
   end if
 next i
 if fl then
   t = 0
   for i = 1 to len( x$ ) then
     if mid$( x$ , i , 1 ) = "e"then t = t + 1
   next i
   if t = 0 or t = 1 then
     t = 0
     for i = 1 to len( x$ ) then
       if mid$( x$ , i , 1 ) = "."then t = t + 1
     next i
     if t = 0 or t = 1 then
       if instr( x$ , "." ) > instr( x$ , "e" ) then fl = 0
     else
       fl = 0
     end if
   else
     fl = 0
   end if
 end if
 isNumber = fl
end function



[tsh73]

Here's test harness from old JB contest about writing "isNumber" function.
BTW I had to comment two THEN in FOR lines - what was it?

data "0", "0.0", "1237", "1728979873987543687681", "5783.23490908654798729"
data "5e46", " -23", "-432.433", "76e-23", "-1.13e-32.2", "abc", "0.1"
data "", "34.2w", "12e13e14", "1.2e345678", "END"

while n$ <> "END"
read n$
print n$, isNumber(n$)
wend

end

function isNumber( x$ )
 nr$ ="-0123456789e."
 x$ = lower$( x$ )
 fl = 1
 for i = 0 to 255
   if not( instr( nr$ , chr$( i ) ) ) then
     if instr( x$ , chr$( i ) ) then fl = 0
   end if
 next i
 if fl then
   t = 0
   for i = 1 to len( x$ ) 'then
     if mid$( x$ , i , 1 ) = "e"then t = t + 1
   next i
   if t = 0 or t = 1 then
     t = 0
     for i = 1 to len( x$ ) 'then
       if mid$( x$ , i , 1 ) = "."then t = t + 1
     next i
     if t = 0 or t = 1 then
       if instr( x$ , "." ) > instr( x$ , "e" ) then fl = 0
     else
       fl = 0
     end if
   else
     fl = 0
   end if
 end if
 isNumber = fl
end function