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(g77-295.info)Expressions in FORMAT Statements

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Expressions in `FORMAT' Statements
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   `g77' doesn't support `FORMAT(I<J>)' and the like.  Supporting this
requires a significant redesign or replacement of `libg2c'.

   However, `g77' does support this construct when the expression is
constant (as of version 0.5.22).  For example:

           PARAMETER (IWIDTH = 12)
     10    FORMAT (I<IWIDTH>)

   Otherwise, at least for output (`PRINT' and `WRITE'), Fortran code
making use of this feature can be rewritten to avoid it by constructing
the `FORMAT' string in a `CHARACTER' variable or array, then using that
variable or array in place of the `FORMAT' statement label to do the
original `PRINT' or `WRITE'.

   Many uses of this feature on input can be rewritten this way as
well, but not all can.  For example, this can be rewritten:

           READ 20, I
     20    FORMAT (I<J>)

   However, this cannot, in general, be rewritten, especially when
`ERR=' and `END=' constructs are employed:

           READ 30, J, I
     30    FORMAT (I<J>)