007001004

📎 7.1.4. Float

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001 The Float datatype representation is two consecutive Integers (see 7.1.5 
002 Integer). The first Integer represents the mantissa of the floating point
003 number and the secong Integer represents the base-10 exponent of the
004 floating pont number. The range of the mantissa is -(2^63) to 2^63 -1
005 and the range of the exponent is -(2^14-1) to 2^14 -1. Mantissa or exponent
006 values outside of the respective accepted range MUST NOT be used in the
007 Float datatype representation. Values typed as Float with a mantissa or
008 exponent outside the accepted range are represented as untyped values,
009 processed by an alternative production of available that ban be used to
010 represent untyped values. Examples of such productions are those whose
011 terminal symbol on the right-hand side is AT(qname) [untyped value]. 
012 AT(*)[untyped value] or CH [untyped value] (See 8.5.4.4.1 Adding
013 Productions when Strict is False).
014
015 The exponent value -(2^14) is used to indicate one of the special values:
016 infinity, negative infinity and not-a-number (NaN). An exponent value 
017 -(2^14) with mantissa values 1 and -1 represents positive infinity (INF)
018 and negative infinity (-INF). An exponent value -(2^14) with any other
019 mantissa value represents NaN.
020
021 The Float datatype representation can be decoded by going through the
022 following  steps.
023
024 1. Retrieve the mantissa value using the procedure described in 7.1.5
025    Integer.
026 2. Retrieve the exponent value using the procedure described in 7.1.5
027    Integer.
028 3. If the exponent value is -(2^14), the mantissa value 1 repreents INF,
029    the mantissa value -1 represents -INF and any other mantissa value 
030    represents NaN. If the exponent value is not -(2^14), the float value
031    is m x 10^e where m is the manissa and e is the exponent obtained in
032    the preceding steps.

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