Postscript: how to convert a integer to string?

Question

In postscript , the cvs *operator* is said to convert a number to a string. How should I use it ? I tried :

100 100 moveto
3.14159 cvs show

or

100 100 moveto
3.14159 cvs string show

but it didn't work.

Any help ?

Answer 1

Try 3.14159 20 string cvs show.

string needs a size and leaves the created string on the stack. cvs needs a value and a string to store the converted value.

If you're doing lots of string conversions, it may be more efficient to create one string and reuse it in each conversion:

/s 20 string def
3.14159 s cvs show

Answer 2

A common idiom is to use a literal string as a template.

1.42857 (       ) cvs show

You can even do formatted output by presenting cvs with various substrings of a larger string.

%0123456.......
(2/7 =         ) dup 6 7 getinterval
2.85714 exch cvs pop show

But the Ghostscript Style Guide forbids this. And it's pretty much the only published Postscript Style Guide we have. (A discussion about this in comp.lang.postscript.) So a common recommendation is to allocate a fresh string when you need it and let the garbage collector earn its keep.

4.28571 7 string cvs show

As a last resort, the truly lazy hacker will hijack =string, the built-in 128-byte buffer used by = and == to output numbers (using, of course, our friend cvs).

5.71428 =string cvs show

And if you like that one, you can combine it with ='s other trick: immediately evaluated names.

{ 7.14285 //=string cvs show }   % embed =string in this procedure

This shaves that extra microsecond off, and makes it much harder to interactively inspect the code. Calling == on this procedure will not reveal the fact that you are using =string; it looks just like any other string.

---

One more trick for the bag, from a post by Helge Blischke in comp.lang.postscript. This is a simple way to get a zero-padded integer.

/bindec         % <integer> bindec <string_of_length_6>
{
        1000000 add 7 string cvs 1 6 getinterval
}bind def