3.2.29. FORMAT(number[,[before][,[after][,[expp][,[expt]]]]])

This function is used to control the format of numbers, and you
may request the size and format in which the number is written.
The parameter number is the number to be formatted, and it must be
a valid REXX number. note that before any conversion or formatting
is done, this number will be normalized according to the current
setting of NUMERIC.

The before and after parameters determines how many characters
that are used before and after the decimal point, respectively.
Note that before does not specify the number of digits in the
integer part, it specifies the size of the field in which the
integer part of the number is written. Remember to allocate space
in this field for a minus too, if that is relevant. If the field
is not long enough to hold the integer part (including a minus if
relevant), an error is reported.

The after parameter will dictate the size of the field in which
the fractional part of the number is written. The decimal point
itself is not a part of that field, but the decimal point will be
omitted if the field holding the fractional part is empty. If
there are less digits in the number than the size of the field, it
is padded with zeros at the right. If there is more digits then it
is possible to fit into the field, the number will be rounded (not
truncated) to fit the field.

Before must at least be large enough to hold the integer part of
number. Therefore it can never be less than 1, and never less than
2 for negative numbers. The integer field will have no leading
zeros, except a single zero digit if the integer part of number is
empty.

The parameter expp the size of the field in which the exponent is
written. This is the size of the numeric part of the exponent, so
the “E” and the sign comes in addition, i.e. the real length if
the exponent is two more than expp specifies. If expp is zero, it
signalizes that exponential form should not be used.  Expp must be
a non-negative whole number. If expp is positive, but not large
enough to hold the exponent, an error is reported.

Expt is the trigger value that decides when to switch from simple
to exponential form. Normally, the default precision (NUMERIC
DIGITS) is used, but if expt is set, it will override that. Note
that if expt is set to zero, exponential form will always be used.
However, if expt tries to force exponential form, simple form will
still be used if expp is zero. Negative values for expt will give
an error. Exponential form is used if more digits than expt is
needed in the integer part, or more than twice expt digits are
needed in the fractional part.

Note that the after number will mean different things in
exponential and simple form.  If after is set to e.g. 3, then in
simple form it will force the precision to 0.001, no matter the
magnitude of the number.  If in exponential form, it will force
the number to 4 digits precision.

     FORMAT(12.34,3,4)        –>   ‘ 12.3400’
     FORMAT(12.34,3,,3,0)     –>   ‘  1.234E+001’
     FORMAT(12.34,3,1)        –>   ‘ 12.3400’
     FORMAT(12.34,3,0)        –>   ‘ 12.3’
     FORMAT(12.34,3,4)        –>   ‘ 12’
     FORMAT(12.34,,,,0)  –>   ‘1.234E+1’
     FORMAT(12.34,,,0)        –>   ‘12.34’
     FORMAT(12.34,,,0,0) –>   ‘12.34’


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