CRAY_FORTRAN(exp or eqn) generates FORTRAN suitable for the CRAY FORTRAN
compilers, e.g., CFT and CIVIC.  It is an extension of the MACSYMA FORTRAN
function, with the following added capabilities:

      1) It knows how to break up an expression which would be more than
         19 continuation lines long into a series of legal FORTRAN statements
         with generated temporary names assigned to the pieces that have
         been broken out.  See below about how to adjust this size.

      2) It converts LOG into ALOG.

      3) It allows an arbitrary character pattern to be substituted for a
         pattern in the FORTRAN output(without regard to line breaks).  This
         is useful for changing subscripts carried formally in variable names
         to values needed in specific DO-LOOPs.
         
      4) It removes the MACSYMA quote character, "\", from the output.

      5) It has the option of returning a character string and generating
         no formatted FORTRAN output.  This is a achieved by setting
         FORT_STRING[FALSE] to TRUE.  This is useful for generating character
         strings for the algebraic operands in FORTRAN logical expressions
         needed by the CRAY "CVMGT" vector merge instruction.

      6) It permits formatted FORTRAN output to be directed to a separate
         file by doing OPEN_FORTRAN_FILE(filespec)$ before and
         CLOSE_FORTRAN_FILE()$ after the appropriate calls to CRAY_FORTRAN.
         The output still goes to the TTY as well.  It is possible to
	 annotate the output to the separate file by use of the command
	 COMMENT_FORTRAN(EXP)$, where EXP is any MACSYMA expression.  The
	 output from COMMENT_FORTRAN does NOT go to the TTY.

      7) It replaces rational constants by constructed names and saves
         the required information in an internal database.  By doing
         GENERATE_DATA_SECTION()$ after the appropriate calls to CRAY_FORTRAN,
         DATA statements are generated which will properly define the
         constructed names.

   The global variables affecting FORTRAN also affect CRAY_FORTRAN in the
same manner.  Additional global variables not mentioned above are:

      FORT_FLOAT[TRUE] should be set to FALSE if the expressions passed
to CRAY_FORTRAN contain only integers and integer variables.

      FORT_POWER_FLOAT[FALSE] - if TRUE, integer exponents are converted
into floating-point numbers in the formatted FORTRAN output.

      ALLOWED_LENGTH[1250] is the number of characters which can be output
in a single FORTRAN statement.  The number 1250 corresponds to a FORTRAN
statement with 19 continuation lines and no indentation.  To add an extra
line with no indentation, increase ALLOWED_LENGTH by 63.  There is a
minimum value for ALLOWED_LENGTH, and CRAY_FORTRAN will reset ALLOWED_LENGTH
to that value if the user has set it to a smaller number.

      BREAK_PREFIX['aa] is the character string used to prefix all symbols
generated to represent subexpressions which had to be broken out of an
expression so that each would result in FORTRAN statements within the
ALLOWED_LENGTH limit.

      SEQUENCE_OPTIM_SUFFIX[?'s] is the string used to suffix symbols
generated to represent subexpressions broken out of an expression by
CRAY_FORTRAN because that expression was too large to be handled by the
CFT(or other appropriate) compiler(The "?" in the default value removes
the internal "$").

      FORTRAN_SUBST_LIST[[]] is the MAXSYMA list of equations used to
perform substring substitutions in the formatted FORTRAN output.  The RHS
of each equation is interpreted as a LISP list of characters(generated for
example by EXPLODEN(?<string>)) to be substituted for a given character
pattern in the output.  This pattern is represented by another LISP list
(similarly generated) in the LHS of the equation.  The CRAY_FORTRAN output
is one long LISP list of characters at the point of comparison.  Note that
the function EXPLODEN is included in the CRAY_FORTRAN FASL file.

   To access CRAY_FORTRAN, do LOAD(CFORTR)$ .  A demonstration can be
found in SHARE1;CFORTR DEMO .  Bugs to GCOOK@MIT-MC .