@node Print, Prompt, Points, Commands

@iftex
@syntax Print.
@end iftex
@example
Syntax: PRINT [+] [ file ] [ 'format' ] @{ list @}
        PRINT [+] [ file ] [ 'format' ] < list >
@end example
@pindex Print
@findex vectors, printing
@findex writing vectors to a file
@findex writing vectors to the screen

Print the vectors specified by @code{list} to @code{file}, if @code{file} is
absent, print to the terminal (the output is paged, sort of).
The name of each vector is printed at the head of the
appropriate column. If the output is going to a file, each line of the
header starts with a `#', so the file can be read without using the
LINES command.

The header is not printed if the variable
@code{print_noheader} is defined and non-zero. For example, I have a macro
@example
p       111     ## print a vector or expression. E.g. "p x" or "p sin(x)"
                local define print_noheader 1
                local set foo=$1
                if(whatis(foo) & 2**5) @{
                   print '%g ' @{ foo @}
                @} else @{
                   print '%s ' @{ foo @}
                @}
                #
@end example
@noindent
to print vectors on a single line.
In addition, no header is printed if you are not actually printing any vectors,
in this case no newline is appended to the string. This provides a way of
controlling string output, and suppressing newlines, e.g.
@code{PRINT 'S' @{@} PRINT 'M\n' @{@}}. You probably will usually want
to use WRITE STANDARD instead (@pxref{Write}).
@findex strings, printing

With the optional `+' the vectors are appended to the file, otherwise
it is overwritten unless @code{$noclobber} is defined, in which case
SM will refuse to touch the file.  You can set @code{noclobber} by
specifying it in your @file{.sm} file.

   The optional format string is of the type accepted by the C function
`printf', and you should see a book on C (or maybe the online system
manual or help command) for more details. Basically, the format string
is copied to the file with format specifiers beginning with @code{%}
signs replaced by the numbers that you want printed. The format
specifiers to use are the floating point ones, @code{%e}
(exponential), @code{%f} (floating point), and @code{%g} (computer's
choice), @code{d}, @code{o}, @code{x} for printing numbers as integers
(the latter two are octal and hexadecimal), or @code{%s} for strings.
Fields are right justified by default, you 
can insert a @code{-} just after the @code{%} to left justify them. A
@code{%} may be written as @code{%%}, and a tab as @code{\t}. Lines
are @emph{not} terminated by a newline by default, you have to write
them explicitly as @code{\n}.

   For example,
@example
SET x=1,10 SET y=x**2
PRINT file '%10f (%10.2e)\n' @{ x y @}
@end example
@noindent
will produce
@example
#........x............y
#
..1.000000.(..1.00e+00)
..2.000000.(..4.00e+00)
..3.000000.(..9.00e+00)
(etc.)
@end example
@noindent
where I have replaced each space by a @code{.} for clarity. If you say
@example
PRINT '%g ' @{ x @}
@end example
@noindent
you will get
@example
..........x

1.2.3.4.5.6.7.8.9.10.
@end example

If you want very long output lines you'll run into one of SM's internal
limits; the maximum length of a string (currently 160 characters).
You might try to work around this
by putting part of the formatted output into string vectors and then using
a %s format to write it out; such an approach can be
made to work, for example instead of
@example
print file 'Date: %2d %2d %4d\n' @{ dd mm yy @}
@end example
@noindent
you can write
@example
set date = sprintf('Date: %2d',dd) + \
           sprintf(' %2d',mm) + \
           sprintf(' %4d',yy)
print file '%s\n' @{ date @}
@end example
@noindent
If you think that this is a hack I rather agree with you, but it does
permit formatted output of up to 400 characters.