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Postscript symbols

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                             Postscript symbols


[ - [ mark

pushes a mark object on the operand stack (see mark). The customary use of
the [ operator is to mark the beginning of an indefinitely long sequence of
objects that will eventually be formed into a new array object by the ]
operator.

ERRORS: stackoverflow

SEE ALSO: ], mark, array, astore
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] mark obj0 ... objn-1 ] array

creates a new array of n elements, where n is the number of elements above
the topmost mark on the operand stack; stores those elements into the
array; and returns the array on the operand stack. The ] operator stores
the topmost object from the stack into element n-1 of array and the
bottommost one (the one immediately above the mark) into element 0 of
array. It removes all the array elements from the stack, as well as the
mark object.

The array is allocated in local or global VM according to the current VM
allocation mode. An invalidaccess error occurs if the array is in global VM
and any of obj0 ... objn-1 are in local VM.

EXAMPLE:
[5 4 3] -> % a 3-element array, with elements 5, 4, 3
mark 5 4 3 counttomark array astore exch pop
-> [5 4 3] [1 2 add] -> % a 1-element array, with element 3

The second line of the example has the same effect as the first, but uses
lowerlevel array and stack manipulation primitives instead of [ and ] In
the last line of the example, note that the PostScript interpreter acts on
all of the array elements as it encounters them (unlike its behavior with
the {...} syntax for executable array construction) so the add operator is
executed before the array is constructed.

ERRORS: stackoverflow, unmatchedmark, VMerror

SEE ALSO: [, mark, array, astore
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<< - << mark

LEVEL 2 pushes a mark object on the operand stack (same as mark and [
operators).

ERRORS: stackoverflow

SEE ALSO: >>, mark
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>> mark key1 value1 ... keyn valuen >> dict LEVEL 2

creates and returns a dictionary containing the specified key-value pairs.
The operands are a mark followed by an even number of objects, which the
operator uses alternately as keys and values to be inserted into the
dictionary. The dictionary is allocated space for precisely the number of
key-value pairs supplied.

The dictionary is allocated in local or global VM according to the current
VM allocation mode. An invalidaccess error occurs if the dictionary is in
global VM and any keys or values are in local VM. A rangecheck error occurs
if there is an odd number of objects above the topmost mark on the stack.

>> is equivalent to:

counttomark 2 idiv dup dict begin
{def} repeat
pop currentdict
end

EXAMPLE:
<< /Duplex true /PageSize [612 792] /Collate false >>
setpagedevice

This example constructs a dictionary containing three key-value pairs,
which it immediately passes to the setpagedevice operator.

ERRORS: invalidaccess, rangecheck, unmatchedmark, VMerror

SEE ALSO: <<, mark, dict
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= any = - pops an object from the operand stack, produces a text
representation of that object's value, and writes the result followed by a
newline character to the standard output file. The text is that produced by
the cvs operator; thus, = prints the value of a number, boolean, string,
name, or operator object and prints --nostringval-- for an object of any
other type.

The name = is not special. In PostScript language programs it must be
delimited by white space or special characters the same as names composed
of alphabetical characters. The value of = is not an operator, but rather a
built-in procedure.

ERRORS: stackunderflow

SEE ALSO: ==, stack, cvs, print, flush
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== any == - pops an object from the operand stack, produces a text
representation of that object followed by a newline character, and writes
the result to the standard output file. == attempts to produce a result
that resembles the PostScript syntax for creating the object.
It precedes literal names by /, brackets strings with (...), and expands
the values of arrays and packed arrays and brackets them with [...] or
{...}. For an object with no printable representation, == produces the name
of its type in the form -mark- or -dict-. For an operator object, it
produces the operator's name in the form --add--.

The name == is not special. In PostScript language programs it must be
delimited by white space or special characters the same as names composed
of alphabetical characters. The value of == is not an operator, but rather
a built-in procedure.

The == operator is intended for convenience in debugging. The details of
how == formats its output are intentionally unspecified. A program
requiring detailed control over output format should do its own formatting
explicitly, using lowerlevel operators, such as cvs. Also, and writeobject
(Level 2 features) may be more suitable for generating machine-readable
output.

ERRORS: stackunderflow

SEE ALSO: =, print, pstack, flush
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$error - $error dict
pushes the dictionary object $error on the operand stack .
$error is not an operator; it is a name in systemdict associated with the
dictionary object.

ERRORS: stackoverflow

SEE ALSO: errordict
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