Comparison of programming languages (associative array): Difference between revisions

Revision as of 13:55, 27 June 2015

Revision as of 09:59, 21 July 2015

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In [[PostScript]], associative arrays are called dictionaries. In Level 1 PostScript they must be created explicitly, but Level 2 introduced direct declaration using the double-brace syntax:

<source lang="postscript">

<code>

% Level 1 declaration

3 dict dup begin

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>>

% Both methods leave the dictionary on the operand stack
</codesource>

Dictionaries can be accessed directly using '''get''' or implicitly by placing the dictionary on the dictionary stack using '''begin''':

<source lang="postscript">

<code>

% With the previous two dictionaries still on the operand stack

/red get print % outputs 'rot'

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begin

green print % outputs 'vert'

end</code>

</source>

Dictionary contents can be iterated through using '''forall''', though not in any particular order:

<source lang="postscript">

<code>

% Level 2 example

<<

Line 972 ⟶ 973:

/That 2

/Other 3

>> {exch =print ( is ) print ==} forall
</codesource>

May well output:

<source lang="postscript">

<code>

That is 2

This is 1

Other is 3
</codesource>

Dictionaries can be augmented (up to their defined size only in Level 1) or altered using '''put''', and entries can be removed using '''undef''':

<source lang="postscript">

<code>

% define a dictionary for easy reuse:

/MyDict <<

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% remove something

MyDict /rouge undef
</codesource>

=== Prolog ===