QUEUES

Section: Miscellaneous Library Functions (3X)
Updated: August 6, 1990
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NAME

queues - tile kernel double linked list extensions

SYNOPSIS

#include queues.f83

queues

DESCRIPTION

The tile forth kernel word set for support of double linked circular lists. Used by the kernel to maintain the run-time queue of tasks for the multi-tasking extension.

: .queue ( queue -- ): Displays information about a queue header or item in the format:
queue# <queue-pointer> succ: <succ-pointer> pred: <pred-pointer>
code ?empty-queue ( queue -- bool): Returns "true" if the queue is empty else "false". Successor pointer points to the queue itself. This definition is also available as forth code for portability to other environments.
: ?map-queue ( queue block[item -- bool] -- ): Used in the following form:
<queue> <conditional-block> ?map-queue
to perform a block of code on each element of the queue until the block returns "true".
: ?member-queue ( item queue -- bool): Search for "item" in "queue". If found returns "true" else "false".
struct.type QUEUE ( -- ): Structure definition of double linked list. Used as follows to create a new queue header instance:
new-struct QUEUE ( -- queue)
A named queue header may be created with:
QUEUE <queue-name> ( -- queue)
Contains two private fields, "+succ" and "+pred".
code dequeue ( item -- ): Removes "item" from any queue. Observe this function does not require knowledge about which queue "item" is a member of. This definition is also available as a colon definition for portability of other environments.
code enqueue ( item queue -- ): Inserts "item" into "queue" as the new predecessor element. If the "queue" parameter is a queue header "item" is inserted last into the queue. "item" must be a pointer to a "QUEUE" field of a structure or a sub-structure of "QUEUE". This definition is also available as a colon definition for portability of other environments.
: map-queue ( queue block[item -- ] -- ): Used in the following form:
<queue> <block> map
Calls the parameter code "block" on each item in the queue.
vocabulary queues ( -- ): Vocabulary containing double linked circular list extensions. Include into the vocabulary search structure, "context", to gain access to these extensions.
: size-queue ( queue -- num): Returns the length of a queue. The queue head is counted. Returns a integer larger than zero.
: succ ( queue1 -- queue2): Returns pointer to successor queue item.
: pred ( queue1 -- queue2): Returns pointer to predecessor queue item.

INTERNALS

Private definitions in the queues vocabulary;

ptr +succ ( queue -- addr) private: Field of the structure type "QUEUE". Modifiers a queue pointer to access successor pointer in queue structure.
ptr +pred ( queue -- addr) private: Field of the structure type "QUEUE". Modifiers a queue pointer to access predecessor pointer in queue structure.

NOTE

The function list is sorted in ASCII order. The type and mode of the entries are indicated together with their parameter stack effect.

COPYING

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Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the section entitled "GNU General Public License" is included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the section entitled "GNU General Public License" may be included in a translation approved by the author instead of in the original English.

AUTHOR

Mikael R.K. Patel
Computer Aided Design Laboratory (CADLAB)
Department of Computer and Information Science
Linkoping University
S-581 83 LINKOPING
SWEDEN
Email: mip@ida.liu.se
y the aut!

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