source: trunk/SRC/ToBeReviewed/STRING/isnumber.pro @ 495

;+
;
; @file_comments
; Determine if a text string is a valid number.
;
; @categories
;
; @param TXT0 {in}{required}
; text string to test.
;
; @param X {in}{required}
;
; @keyword HELP
;
; @returns
;       x = optionally returned numeric value if valid.
;       i = test flag:
;           0: not a number.
;           1: txt is a long integer.
;           2: txt is a float.
;           -1: first word of txt is a long integer.
;           -2: first word of txt is a float.
;
; @history
;  - R. Sterner.  15 Oct, 1986. Johns Hopkins Applied Physics Lab.
;  - R. Sterner, 12 Mar, 1990 --- upgraded.
;  - Richard Garrett, 14 June, 1992 --- fixed bug in returned float value.
;  - R. Sterner, 1999 Nov 30 --- Fixed a bug found by Kristian Kjaer, Denmark
;
; Copyright (C) 1986, Johns Hopkins University/Applied Physics Laboratory
; This software may be used, copied, or redistributed as long as it is not
; sold and this copyright notice is reproduced on each copy made.  This
; routine is provided as is without any express or implied warranties
; whatsoever.  Other limitations apply as described in the file disclaimer.txt.
;
; @version
; $Id$
;
;-
FUNCTION isnumber, txt0, x, HELP=hlp
;
  compile_opt idl2, strictarrsubs
;
        if (n_params(0) lt 1) or keyword_set(hlp) then begin
          print,' Determine if a text string is a valid number.'
          print,' i = isnumber(txt, [x])'
          print,'   txt = text string to test.                      in'
          print,'   x = optionally returned numeric value if valid.  out'
          print,'   i = test flag:                                  out'
          print,'       0: not a number.'
          print,'       1: txt is a long integer.'
          print,'       2: txt is a float.'
          print,'       -1: first word of txt is a long integer.'
          print,'       -2: first word of txt is a float.'
          return, -1
        endif

        txt = strtrim(txt0,2)   ; trim blanks.
        x = 0                   ; define X.

        if txt eq '' then return, 0     ; null string not a number.

        sn = 1
        if nwrds(txt) gt 1 then begin   ; get first word if more than one.
          sn = -1
          txt = getwrd(txt,0)
        endif
        
        f_flag = 0                      ; Floating flag.
        b = byte(txt)                   ; Convert to byte array.
        if b[0] eq 45 then b=b[1:*]     ; Drop leading '-'.   ; Kristian Kjaer
        if b[0] eq 43 then b=b[1:*]     ; Drop leading '+'.   ; bug fix.
        w = where(b eq 43, cnt)         ; Look for '+'
        if cnt gt 1 then return, 0      ; Allow only 1.
        t = delchr(txt,'+')             ; Drop it.
        w = where(b eq 45, cnt)         ; Look for '-'
        if cnt gt 1 then return, 0      ; Allow only 1.
        t = delchr(t,'-')               ; Drop it.
        w = where(b eq 46, cnt)         ; Look for '.'
        if cnt gt 1 then return, 0      ; Allow only 1.
        if cnt eq 1 then f_flag = 1     ; If one then floating.
        t = delchr(t,'.')               ; Drop it.
        w = where(b eq 101, cnt)        ; Look for 'e'
        if cnt gt 1 then return, 0      ; Allow only 1.
        if cnt eq 1 then f_flag = 1     ; If 1 then assume float.
        t = delchr(t,'e')               ; Drop it.
        w = where(b eq 69, cnt)         ; Look for 'E'
        if cnt gt 1 then return, 0      ; Allow only 1.
        if cnt eq 1 then f_flag = 1     ; If 1 then assume float.
        t = delchr(t,'E')               ; Drop it.
        w = where(b eq 100, cnt)        ; Look for 'd'
        if cnt gt 1 then return, 0      ; Allow only 1.
        if cnt eq 1 then f_flag = 1     ; If 1 then assume float.
        t = delchr(t,'d')               ; Drop it.
        w = where(b eq 68, cnt)         ; Look for 'D'
        if cnt gt 1 then return, 0      ; Allow only 1.
        if cnt eq 1 then f_flag = 1     ; If 1 then assume float.
        t = delchr(t,'D')               ; Drop it.
        ;-----  Allow only one 'e', 'E', 'd', or 'D'  --------
        if total((b eq 101)+(b eq 69)+(b eq 100)+(b eq 68)) gt 1 then return,0
        b = byte(t)
        ;-----  Allow no alphabetic characters  -----------
        if total((b ge 65) and (b le 122)) ne 0 then return, 0

        c = strmid(t,0,1)
        if (c lt '0') or (c gt '9') then return, 0  ; First char not a digit.

        x = txt + 0.0                               ; Convert to a float.
        if f_flag eq 1 then return, 2*sn            ; Was floating.
        if x eq long(x) then begin
          x = long(x)
          return, sn
        endif else begin
          return, 2*sn
        endelse

        end