Attempts to handle MSBuild condition attributes

Iterative parser.fsx

let input = @"$(SolutionDir) == '' Or $(SolutionDir) == '*Undefined*' And $(Configuration) == 'Debug'"

let rec parseWord (data : System.Text.StringBuilder) (input : string) (index : int) (inQuotes : bool) : string * int =
    let substr = input.Substring(index)
    let f i () = (data.ToString()), (index + i)
    let ret = f 1
    if input.Length = index
    then f 0 ()
    else
        let c = input.[index]
        if data.Length = 0 && not inQuotes && c = '\''
        then parseWord data input (index + 1) true
        elif inQuotes && c = '\''
        then ret()
        elif not inQuotes && c = ' ' && data.Length = 0
        then parseWord data input (index + 1) inQuotes
        elif not inQuotes && c = ' '
        then ret()
        else parseWord (data.Append(c)) input (index + 1) inQuotes

let sb = new System.Text.StringBuilder()
let (firstWord, index) = parseWord sb input 0 false
sb.Clear()

let rec parseComparison (data : System.Text.StringBuilder) (input : string) (index : int) : string * int =
    let substr = input.Substring(index)
    if input.Length = index
    then "", index
    else
        let c = input.[index]
        if data.Length = 0 && c = ' '
        then parseComparison data input (index + 1)
        elif data.Length = 2 && c <> ' '
        then "", index 
        elif c = '<' || c = '>' || c = '!' || c = '='
        then parseComparison (data.Append(c)) input (index + 1)
        else (data.ToString()), index

let (comp, index') = parseComparison sb input index
sb.Clear()
let (secondWord, index'') = parseWord sb input index' false