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FloatStr, MantissaAndExponent

Syntax

FloatStr(X:RAT):STRING
FloatStr(X:RAT, Prec:INT):STRING
MantissaAndExponent(X:RAT, Prec:INT):RECORD
    

Summary

convert rational number to a float string

Description

The first two functions convert a rational number X into a (decimal) floating point string. The optional second argument Prec says how many decimal digits to include in the mantissa; the default value is 10. Note that an exponent is always included; the only exception being the number zero which is converted to the string 0.

The third function converts a rational number into a Record with components named Mantissa and Exponent. The value of the Exponent field is the unique integer E such that 1 <= X*10^E <= 10, and the value of Mantissa is the nearest integer to (X*10^E)*10^(Prec-1). As an exception the case of X=0 always produces zero values for both components of the record.

example

    
FloatStr(2/3);         -- last printed digit is rounded
6.666666667*10^(-1)
-------------------------------
FloatStr(7^510);       -- no arbitrary limit on exponent range
1.000000938*10^431
-------------------------------
FloatStr(1/81, 50);    -- precision of mantissa specified by user
1.2345679012345679012345679012345679012345679012346*10^(-2)
-------------------------------
FloatStr(1/2);         -- trailing zeroes are not suppressed
5.000000000*10^(-1)
-------------------------------
MantissaAndExponent(1/2,3);           --  1/2 = 5.00*10^(-1)
Record[Exponent = -1, Mantissa = 500]
-------------------------------
MantissaAndExponent(0.9999, 3);       --  0.9999 rounds up to give 1.00
Record[Exponent = 0, Mantissa = 100]
-------------------------------
        
    

See Also