12 The optional Floating-Point word set

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:

Rationale:

>FLOAT enables programs to read floating-point data in legible ASCII format. It accepts a much broader syntax than does the text interpreter since the latter defines rules for composing source programs whereas >FLOAT defines rules for accepting data. >FLOAT is defined as broadly as is feasible to permit input of data from Forth-2012 systems as well as other widely used standard programming environments.

This is a synthesis of common FORTRAN practice. Embedded spaces are explicitly forbidden in much scientific usage, as are other field separators such as comma or slash.

While >FLOAT is not required to treat a string of blanks as zero, this behavior is strongly encouraged, since a future version of this standard may include such a requirement.

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