Re: So...what if I wanted to do something like atof?
Hi Jonas,
>Anyway, I have been working on a project using Euphoria and Win32Lib. I
>have an edit control where I want the user to enter a price. I want to
>convert and store that sequence as a floating point. In C++ I would have
>probably used atof() to do that conversion. What is the functional
>equivalent in Euphoria?
Of course when you use getText() to retrieve whatever the user entered, you
get a Euphoria sequence returned. This can be thought of a "string" field.
But what you need in your program is to treat the user data as a monetary
amount. Both integer and floating point numbers can be stored in a Euphoria
atom. So the problem is "how to convert a sequence to an atom".
Euphoria provides a very simplistic function, value(), which can do this for
you. However, it has limitations that make it unusable in real-world
applications. For example, it stops conversion when it finds a non-digit but
still reports success. So if the user enters "12o.99" it will successfully
return the value of 12 rather than generate an error.
A number of people on the list have already created another version of
value(), including myself, which handles a larger range of possible user
input. Below is some code of mine that you can use as you see fit.
-----------------------
constant TRUE = (1=1), FALSE = (0=1)
integer vBase, vPeriod, vComma, vMoney
sequence vLegalChars
vBase = 10
vPeriod = '.'
vComma = ','
vMoney = '$'
vLegalChars = "0123456789abcdef-+.,"
----------------------------------------------------------------------------
---
-- Sets the default number base to be used when converting strings to
numbers.
global function setnumberbase(integer pNewBase)
integer lOldBase
lOldBase = vBase
if pNewBase > 1 and pNewBase <= 16 then
vBase = pNewBase
end if
return lOldBase
end function
----------------------------------------------------------------------------
---
-- Sets the default punctuation characters.
-- If any parameter is zero, then the corresponding punctuation symbol is
not changed.
-- All three punctuation symbols must be different from each other.
-- Returns a sequence of three elements containing the current punctuation
chars.
-- 1) The 'decimal place' character. Initially '.'
-- 2) The digit separator character. Initially ','
-- 3) The money symbol. Initially '$'
global function setnumberpunct(integer pPeriod, integer pComma, integer
pMoney)
sequence lOldValues
lOldValues = {vPeriod, vComma, vMoney}
if pPeriod >= 0 and pPeriod <= 255 then
vPeriod = pPeriod
end if
if pComma >= 0 and pComma <= 255 then
vComma = pComma
end if
if pMoney >= 0 and pMoney <= 255 then
vMoney = pMoney
end if
if (vPeriod = vComma)
or (vPeriod = vMoney)
or (vComma = vMoney)
then
-- Duplicate chars used so revert.
vPeriod = lOldValues[1]
vComma = lOldValues[2]
vMoney = lOldValues[3]
else
vLegalChars = "0123456789abcdef-+" & vPeriod & vComma
end if
return lOldValues
end function
----------------------------------------------------------------------------
---
-- Converts a text sequence to a number (atom).
-- Leading and trailing spaces are ignored.
-- If the text is enclosed in parenthesis, a negative number is returned.
-- If the number begins with ...
-- [Money Symbol] : base is assumed as 10
-- # : base is assumed as 16 (Hexadecimal)
-- 0x : base is assumed as 16 (Hexadecimal)
-- 0b : base is assumed as 2 (Binary)
-- 0d : base is assumed as 16 (Decimal)
-- 0O : base is assumed as 8 (Octal)
-- x' : base is assumed as 16 (Hexadecimal) and final char is dropped
-- b' : base is assumed as 2 (Binary) and final is char dropped
-- d' : base is assumed as 16 (Decimal) and final char is dropped
-- O' : base is assumed as 8 (Octal) and final char is dropped
--
-- The text can have a single '-' or '+', either before or after the number.
-- Base 10 numbers can have digit separators. eg. 12,345.678,9
--
-- The function returns a 3-element sequence.
-- 1) 0 ==> The input had some invalid format. Either a subsequence,
-- a non-integer atom,
-- or a character other than 0-9 a-f "+-", decimal or separator
symbol
-- or money symbol not in front of the number
-- or a digit not in the current number base.
-- 1 ==> No invalid elements were found.
-- 2) The converted number (or as much as could be converted)
-- 3) The index into the input were conversion stopped. Use this as an
-- error marker if a zero was returned in the first element.
--
-- Examples:
-- sequence rc
-- rc = seqtonumber(" $2,150.95")
-- ? rc -- {1,2150.95,11}
--
-- rc = seqtonumber("1234-")
-- ? rc -- {1,-1234,6}
--
-- rc = seqtonumber("0xff73")
-- ? rc -- {1,65395,7}
--
-- rc = seqtonumber("b'001101'")
-- ? rc -- {1,13,9} (The final ' is ignored)
--
-- rc = seqtonumber("12 Cats")
-- ? rc -- {0,12,3}
--
-- rc = seqtonumber("12.3.3 Cats")
-- ? rc -- {0,12.3,5}
--
---- Valid "number" modifier prefixes.
constant kNumStarts =
{
{"0X", 256, 16, 0},
{"0O", 256, 8, 0},
{"0B", 11, 2, 0},
{"0D", 13, 10, 0},
{"X'", 256, 16, 1},
{"D'", 256, 10, 1},
{"O'", 256, 8, 1},
{"B'", 256, 2, 1}
}
--------------------------------------------
global function seqtonumber(sequence pData)
--------------------------------------------
atom lResult
integer lDotFound, lSign, lPos, lOk, lChar, lValue
atom lRHS, lLHS, lRHSdepth, lFullValue
integer lBase, lUsingRHS, lCommas
integer lStart, lEnd, lConvStarted, lTrailingSign
sequence lTemp
lResult = 0
lDotFound = FALSE
lSign = 0
lUsingRHS = 0
lConvStarted = FALSE
lTrailingSign = FALSE
lRHS = 0
lRHSdepth = 1
lLHS = 0
lBase = vBase
-- Disregard trailing and leading blanks
lStart = length(pData) + 1
for i = 1 to length(pData) do
if pData[i] != ' ' then
lStart = i
exit
end if
end for
lEnd = 0
for i = length(pData) to 1 by -1 do
if pData[i] != ' ' then
lEnd = i
exit
end if
end for
-- Look for parenthesized numbers.
if equal('(', pData[lStart]) and equal(')', pData[lEnd]) then
lStart += 1
lEnd -= 1
lSign = -1
end if
-- Examine for special start codes.
if lEnd - lStart >= 0
then
if equal(vMoney, pData[lStart]) then
-- Cater for spaces between the $ and first digit.
for i = lStart+1 to lEnd do
if pData[i] != ' ' then
lStart = i
exit
end if
end for
lBase = 10
elsif equal('#', pData[lStart]) then
lBase = 16
lStart += 1
elsif lStart != length(pData) then
lTemp = upper(pData[lStart .. lStart + 1])
for i = 1 to length(kNumStarts) do
if equal(lTemp, kNumStarts[i][1]) then
if lBase < kNumStarts[i][2] then
lBase = kNumStarts[i][3]
lStart += length(kNumStarts[i][1])
lEnd -= kNumStarts[i][4]
exit
end if
end if
end for
end if
end if
-- Only base-10 can have commas
if lBase != 10 then
lCommas = FALSE
else
lCommas = TRUE
end if
-- Start parsing the string.
lPos = lStart
lOk = TRUE
while TRUE do
-- No more characters?
if lPos > lEnd then
exit
end if
-- Check for embedded sequences
if sequence(pData[lPos]) then
lOk = FALSE
exit
end if
-- Check for non-integer elements.
if not integer(pData[lPos]) then
lOk = FALSE
exit
end if
-- Pluck out the next char to examine.
lChar = lower(pData[lPos])
-- Is it legal char.?
lValue = find(lChar, vLegalChars) - 1
if lValue < 0 then
lOk = FALSE
exit
end if
-- Values below the base are useable digits.
if lValue < lBase then
-- This prevents embedded signs.
if lTrailingSign = TRUE then
lOk = FALSE
exit
end if
-- Signal that conversion is underway.
lConvStarted = TRUE
-- Am I doing the Left or Right side of the "decimal" symbol?
if lUsingRHS then
-- Right side.
-- Accume that value so far.
lRHS = (lRHS * lBase) + lValue
-- Calculate the RHS divisor
lRHSdepth *= lBase
else
-- Left side.
-- Accume the value so far.
lLHS = (lLHS * lBase) + lValue
end if
else
-- Start checking for special symbols.
-- A negative sign?
if lChar = '-' then
-- If I haven't found one yet then mark this a -ve number
-- and if conversion had started, its a trailing sign.
if lSign = 0 then
lSign = -1
lTrailingSign = lConvStarted
else
-- Duplicate sign symbol detected.
lOk = FALSE
exit
end if
-- A positive sign?
elsif lChar = '+' then
-- If I haven't found one yet then mark this a +ve number
-- and if conversion had started, its a trailing sign.
if lSign = 0 then
lSign = 1
lTrailingSign = lConvStarted
else
-- Duplicate sign symbol detected.
lOk = FALSE
exit
end if
-- A decimal position symbol?
elsif lChar = vPeriod then
-- If I haven't found one yet then mark that I now have
-- and start processing the right hand side.
if lDotFound = FALSE then
lDotFound = TRUE
lUsingRHS = TRUE
else
-- A duplicate decimal symbol found.
lOk = FALSE
exit
end if
-- A digit separator?
elsif lChar = vComma then
-- If this base is not allowed digit separators, flag an
error.
if lCommas = FALSE then
lOk = FALSE
exit
end if
else
-- Must be a non-legal character for current number base.
lOk = FALSE
exit
end if
end if
-- Bump to next input character.
lPos += 1
end while
-- If no sign symbols used, assume a positive number.
if lSign = 0 then
lSign = 1
end if
-- Calculate the actual value represented by the string.
lFullValue = lSign *(lLHS + (lRHS / lRHSdepth))
return {lOk, lFullValue, lPos}
end function
----------------------------------
cheers,
Derek Parnell
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