The specification of >FLOAT in DPANS94 suggests that it treat a string
of blanks as a representation of zero (below). Common practice among
Forth systems (pfe, gforth, bigforth) appears to extend this suggested
behavior to null strings as well, e.g.
s" " >FLOAT
returns a true flag on the stack, and fp zero on the floating point
stack. Is there a strong argument for considering a null string to be a
valid representation of fp zero. I would have implemented the conversion
to return a false flag. Also, I don't much like the idea of treating a
string of blanks as a valid representation for 0E either, but perhaps
there was some valid reason for suggesting this behavior.
Krishna
--
12.6.1.0558 >FLOAT
to-float FLOATING
( c-addr u -- true | false ) ( F: -- r | )
or ( c-addr u -- r true | false)
An attempt is made to convert the string specified by c-addr and u to
internal floating-point representation. If the string represents a valid
floating-point number in the syntax below, its value r and true are
returned. If the string does not represent a valid floating-point number
only false is returned.
A string of blanks should be treated as a special case representing zero.
The syntax of a convertible string := <significand>[<exponent>]
<significand> := [<sign>]{<digits>[.<digits0>] |
..<digits> }
<exponent> := <marker><digits0>
<marker> := {<e-form> | <sign-form>}
<e-form> := <e-char>[<sign-form>]
<sign-form> := { + | - }
<e-char> := { D | d | E | e }
See: A.12.6.1.0558 >FLOAT
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