Various corrections to chapter 22.

[mudman.git] / md / language.md

diff --git a/md/language.md b/md/language.md
index 0abf4dfc4871ddb754e8fc4025f2acc9678de879..7a8b684274a250efdcfcaa81595794e78952f2d8 100644 (file)
--- a/md/language.md
+++ b/md/language.md
@@ -19,21 +19,21 @@ This document is free of known copyright restrictions.
 Abstract
 ========
 
 Abstract
 ========
 

-The Muddle programming language began existence in late 1970 (under
-the name Muddle) as a successor to Lisp (Moon, 1974), a candidate
-vehicle for the Dynamic Modeling System, and a possible base for
-implementation of Planner (Hewitt, 1969). The original design goals
-included an interactive integrated environment for programming,
-debugging, loading, and editing: ease in learning and use; facilities
-for structured, modular, shared programs; extensibility of syntax,
-data types and operators: data-type checking for debugging and
-optional data-type declarations for compiled efficiency; associative
-storage, coroutining, and graphics. Along the way to reaching those
-goals, it developed flexible input/output (including the ARPA
-Network), and flexible interrupt and signal handling. It now serves as
-a base for software prototyping, research, development, education, and
-implementation of the majority of programs at MIT-DMS: a library of
-sharable modules, a coherent user interface, special research
+The Muddle programming language began existence in late 1970 as a 
+successor to Lisp (Moon, 1974), a candidate vehicle for the Dynamic 
+Modeling System, and a possible base for implementation of Planner 
+(Hewitt, 1969). The original design goals included an interactive 
+integrated environment for programming, debugging, loading, and 
+editing: ease in learning and use; facilities for structured, 
+modular, shared programs; extensibility of syntax, data types and 
+operators: data-type checking for debugging and optional data-type 
+declarations for compiled efficiency; associative storage, 
+coroutining, and graphics. Along the way to reaching those goals, it 
+developed flexible input/output (including the ARPA Network), and 
+flexible interrupt and signal handling. It now serves as a base for 
+software prototyping, research, development, education, and 
+implementation of the majority of programs at MIT-DMS: a library of 
+sharable modules, a coherent user interface, special research 

 projects, autonomous daemons, etc.
 
 This document was originally intended to be a simple low-level
 projects, autonomous daemons, etc.
 
 This document was originally intended to be a simple low-level


@@ -125,16 +125,16 @@ on.
 
 There are no "practice problems"; you are assumed to be learning
 Muddle for some purpose, and your work in achieving that purpose will
 
 There are no "practice problems"; you are assumed to be learning
 Muddle for some purpose, and your work in achieving that purpose will

-be more useful and motivated than artificial problems. In several
+be more useful and motivating than artificial problems. In several

 cases, the examples contain illustrations of important points which
 cases, the examples contain illustrations of important points which

-are not covered in the text. Ignore examples as your peril.
+are not covered in the text. Ignore examples at your peril.

 
 This document does not assume knowledge of any specific programming
 
 This document does not assume knowledge of any specific programming

-language on the \[sic\] your part. However, "computational literacy"
-is assumed: you should have written at least one program before. Also
-very little familiarity is assumed with the interactive time-sharing
-operating systems under which Muddle runs -- ITS, Tenex, and Tops-20
--- namely just file and user naming conventions.
+language on your part. However, "computational literacy" is assumed:
+you should have written at least one program before. Also very little
+familiarity is assumed with the interactive time-sharing operating
+systems under which Muddle runs -- ITS, Tenex, and Tops-20 -- namely
+just file and user naming conventions.

 
 ### Notation
 
 
 ### Notation
 


@@ -175,8 +175,8 @@ especially upon reaching chapter 5 (Simple Functions).
 -------------------------
 
 First, catch your rabbit. Somehow get the interpreter running -- the
 -------------------------
 
 First, catch your rabbit. Somehow get the interpreter running -- the

-program in the file `SYS:TS.Muddle` in the ITS version or
-`SYS:Muddle.SAV` in the Tenex version or `SYS:Muddle.EXE` in the
+program in the file `SYS:TS MDL` in the ITS version or
+`SYS:MDL.SAV` in the Tenex version or `SYS:MDL.EXE` in the

 Tops-20 version. The interpreter will first type out some news
 relating to Muddle, if any, then type
 
 Tops-20 version. The interpreter will first type out some news
 relating to Muddle, if any, then type
 


@@ -231,9 +231,8 @@ except that, if your terminal is a "display" terminal (for example,
 IMLAC, ARDS, Datapoint), it firsts clears the screen.
 
 Typing `^G` (`CTRL`+`G`) causes Muddle to stop whatever it is doing
 IMLAC, ARDS, Datapoint), it firsts clears the screen.
 
 Typing `^G` (`CTRL`+`G`) causes Muddle to stop whatever it is doing

-and act as if an error had occurred ([section
-1.4](#14-errors-simple-considerations-1)). `^G` is generally most
-useful for temporary interruptions to check the progress of a
+and act as if an error had occurred (section 1.4). `^G` is generally
+most useful for temporary interruptions to check the progress of a

 computation. `^G` is "reversible" -- that is, it does not destroy any
 of the "state" of the computation it interrupts. To "undo" a `^G`,
 type the characters
 computation. `^G` is "reversible" -- that is, it does not destroy any
 of the "state" of the computation it interrupts. To "undo" a `^G`,
 type the characters


@@ -243,11 +242,11 @@ type the characters
 (This is discussed more fully far below, in section 16.4.)
 
 Typing `^S` (`CTRL`+`S`) causes Muddle to **throw away** what it is
 (This is discussed more fully far below, in section 16.4.)
 
 Typing `^S` (`CTRL`+`S`) causes Muddle to **throw away** what it is

-currently doing and return a normal "listening" state. (In the Tenex
-and Tops-20 versions, `^O` also should have the same effect.) `^S` is
-generally most useful for aborting infinite loops and similar terrible
-things. `^S` **destroys** whatever is going on, and so it is **not**
-reversible.
+currently doing and return to a normal "listening" state. (In the
+Tenex and Tops-20 versions, `^O` also should have the same effect.)
+`^S` is generally most useful for aborting infinite loops and similar
+terrible things. `^S` **destroys** whatever is going on, and so it is
+**not** reversible.

 
 Most expressions in Muddle include "brackets" (generically meant) that
 must be correctly paired and nested. If you end your typing with the
 
 Most expressions in Muddle include "brackets" (generically meant) that
 must be correctly paired and nested. If you end your typing with the


@@ -1180,7 +1179,7 @@ re-bound....)
 One way to "name" a `FUNCTION` is
 
     <SETG SQUARE #FUNCTION ((X) <* .X .X>)>$
 One way to "name" a `FUNCTION` is
 
     <SETG SQUARE #FUNCTION ((X) <* .X .X>)>$

-    #FUNCTION ((X) <* .X .X>
+    #FUNCTION ((X) <* .X .X>)

 
 So that
 
 
 So that
 


@@ -1192,7 +1191,7 @@ So that
 Another way, which is somewhat cleaner in its typing:
 
     <SETG SQUARE <FUNCTION (X) <* .X .X>>>$
 Another way, which is somewhat cleaner in its typing:
 
     <SETG SQUARE <FUNCTION (X) <* .X .X>>>$

-    #FUNCTION ((X) <* .X .X>
+    #FUNCTION ((X) <* .X .X>)

 
 `FUNCTION` is an `FSUBR` which simply makes a `FUNCTION` out of its
 arguments and returns the created `FUNCTION`.
 
 `FUNCTION` is an `FSUBR` which simply makes a `FUNCTION` out of its
 arguments and returns the created `FUNCTION`.


@@ -4132,30 +4131,30 @@ used on the `CHANNEL`, and whether or not the *device* is a terminal.
 The following table tells which `SUBR`s can be used with which modes,
 where `OK` indicates an allowed use:
 
 The following table tells which `SUBR`s can be used with which modes,
 where `OK` indicates an allowed use:
 

-  -------------------------------------------------------------------------------------------------------------------------------------------------
-  "READ"               "PRINT"               "READB"               "PRINTB", "PRINTO"                           mode / SUBRs
-  -------------------- --------------------- --------------------- -------------------------------------------- -----------------------------------
-  OK                                         OK                                                                 `READ` `READCHR` `NEXTCHR`
-                                                                                                                `READSTRING` `FILECOPY`
-                                                                                                                `FILE-LENGTH LOAD`
+  -------------------------------------------------------------------------
+  "READ" "PRINT" "READB" "PRINTB", "PRINTO" mode / SUBRs
+  ------ ------- ------- ------------------ ------------
+  OK             OK                         `READ` `READCHR` `NEXTCHR`
+                                            `READSTRING` `FILECOPY`
+                                            `FILE-LENGTH LOAD`

 
 

-                       OK                                          OK\*                                         `PRINT` `PRIN1` `PRINC` `IMAGE`
-                                                                                                                `CRLF` `TERPRI` `FILECOPY`
-                                                                                                                `PRINTSTRING` `BUFOUT` `NETS`
-                                                                                                                `RENAME`
+         OK              OK\*               `PRINT` `PRIN1` `PRINC` `IMAGE`
+                                            `CRLF` `TERPRI` `FILECOPY`
+                                            `PRINTSTRING` `BUFOUT` `NETS`
+                                            `RENAME`

 
 

-                                             OK                                                                 `READB` `GC-READ`
+                 OK                         `READB` `GC-READ`

 
 

-                                                                   OK                                           `PRINTB` `GC-DUMP`
+                         OK                 `PRINTB` `GC-DUMP`

 
 

-  OK                                         OK                    OK                                           `ACCESS`
+  OK             OK      OK                 `ACCESS`

 
 

-  OK                   OK                    OK                    OK                                           `RESET`
+  OK     OK      OK      OK                 `RESET`

 
 

-  OK                   OK                                                                                       `ECHOPAIR`
+  OK     OK                                 `ECHOPAIR`

 
 

-  OK                                                                                                            `TTYECHO` `TYI`
-  -------------------------------------------------------------------------------------------------------------------------------------------------
+  OK                                        `TTYECHO` `TYI`
+  -------------------------------------------------------------------------

 
 `*` PRINTing (or `PRIN1`ing) an `RSUBR` (chapter 19) on a `"PRINTB"`
 or `"PRINTO"` `CHANNEL` has special effects.
 
 `*` PRINTing (or `PRIN1`ing) an `RSUBR` (chapter 19) on a `"PRINTB"`
 or `"PRINTO"` `CHANNEL` has special effects.


@@ -4278,52 +4277,52 @@ each element, and an interpretation. The format used is the following:
 
 *element-number: type interpretation*
 
 
 *element-number: type interpretation*
 

-  ----------------------------------------------------------------------------------------------------
-  element-number             type               interpretation
-  -------------------------- ------------------ ------------------------------------------------------
-  -1                         `LIST`             transcript channel(s) (see below)
+  -------------------------------------------------------------------------------------
+  element-number   type          interpretation
+  ---------------- ------------- ------------------------------------------------------
+  -1               `LIST`        transcript channel(s) (see below)

 
 

-  \* 0                       varies             device-dependent information
+  \* 0             varies        device-dependent information

 
 

-  \* 1                       `FIX`              channel number (ITS) or JFN (Tenex and Tops-20), `0`
-                                                for internal or closed
+  \* 1             `FIX`         channel number (ITS) or JFN (Tenex and Tops-20), `0`
+                                 for internal or closed

 
 

-  \* 2                       `STRING`           mode
+  \* 2             `STRING`      mode

 
 

-  \* 3                       `STRING`           first file name argument
+  \* 3             `STRING`      first file name argument

 
 

-  \* 4                       `STRING`           second file name argument
+  \* 4             `STRING`      second file name argument

 
 

-  \* 5                       `STRING`           device name argument
+  \* 5             `STRING`      device name argument

 
 

-  \* 6                       `STRING`           directory name argument
+  \* 6             `STRING`      directory name argument

 
 

-  \* 7                       `STRING`           real first file name
+  \* 7             `STRING`      real first file name

 
 

-  \* 8                       `STRING`           real second file name
+  \* 8             `STRING`      real second file name

 
 

-  \* 9                       `STRING`           real device name
+  \* 9             `STRING`      real device name

 
 

-  \* 10                      `STRING`           real directory name
+  \* 10            `STRING`      real directory name

 
 

-  \* 11                      `FIX`              various status bits
+  \* 11            `FIX`         various status bits

 
 

-  \* 12                      `FIX`              PDP-10 instruction used to do one I/O operation
+  \* 12            `FIX`         PDP-10 instruction used to do one I/O operation

 
 

-  13                         `FIX`              number of characters per line of output
+  13               `FIX`         number of characters per line of output

 
 

-  14                         `FIX`              current character position on a line
+  14               `FIX`         current character position on a line

 
 

-  15                         `FIX`              number of lines per page
+  15               `FIX`         number of lines per page

 
 

-  16                         `FIX`              current line number on a page
+  16               `FIX`         current line number on a page

 
 

-  17                         `FIX`              access pointer for file-oriented devices
+  17               `FIX`         access pointer for file-oriented devices

 
 

-  18                         `FIX`              radix for `FIX` conversion
+  18               `FIX`         radix for `FIX` conversion

 
 

-  19                         `FIX`              sink for an internal `CHANNEL`
-  ----------------------------------------------------------------------------------------------------
+  19               `FIX`         sink for an internal `CHANNEL`
+  -------------------------------------------------------------------------------------

 
 N.B.: The elements of a `CHANNEL` below number 1 are usually invisible
 but are obtainable via `<NTH <TOP channel> fix>`, for some appropriate
 
 N.B.: The elements of a `CHANNEL` below number 1 are usually invisible
 but are obtainable via `<NTH <TOP channel> fix>`, for some appropriate


@@ -8400,9 +8399,9 @@ when space becomes full varies, as discussed below.
 
 Most storage used explicitly by Muddle programs is obtained from a
 pool of free storage managed by a "garbage collector". Storage is
 
 Most storage used explicitly by Muddle programs is obtained from a
 pool of free storage managed by a "garbage collector". Storage is

-obtained from this pool by the `SUBR`s which construct objects. When a
-`SUBR` finds that the pool of available storage is exhausted, it
-automatically calls the garbage collector.
+obtained from this pool by the `SUBR`s which construct objects. When
+such a `SUBR` finds that the pool of available storage is exhausted,
+it automatically calls the garbage collector.

 
 The garbage collector has two algorithms available to it: the
 "copying" algorithm, which is used by default, and the "mark-sweep"
 
 The garbage collector has two algorithms available to it: the
 "copying" algorithm, which is used by default, and the "mark-sweep"


@@ -8431,7 +8430,7 @@ Only when the total system resources are exhausted will you finally
 lose.
 
 Thus, if you just "forget about" an object, that is, lose all possible
 lose.
 
 Thus, if you just "forget about" an object, that is, lose all possible

-means of referencing it, its storage is automatically reclaimed.
+means of referencing it, its storage area is automatically reclaimed.

 "Object" in this context includes that stack-structured storage space
 used in `PROCESS`es for functional application.
 
 "Object" in this context includes that stack-structured storage space
 used in `PROCESS`es for functional application.
 


@@ -8556,8 +8555,9 @@ becomes full, Muddle goes through the following procedure:
 5.  Finally, the "mark-sweep" algorithm sweeps through the storage
     space, adding unmarked objects to the internal free lists for
     later re-use. The "copying" algorithm maps the inferior process's
 5.  Finally, the "mark-sweep" algorithm sweeps through the storage
     space, adding unmarked objects to the internal free lists for
     later re-use. The "copying" algorithm maps the inferior process's

-    address space into Muddle's own, replacing old garbagey with the
-    new compact storage, and the inferior process is destroyed.
+    address space into Muddle's own, replacing old garbagey storage
+    with the new compact storage, and the inferior process is
+    destroyed.

 
 22.5 GC
 -------
 
 22.5 GC
 -------


@@ -8566,24 +8566,44 @@ becomes full, Muddle goes through the following procedure:
 
 causes the garbage collector to run and returns the total number of
 words of storage reclaimed. All of its arguments are optional: if they
 
 causes the garbage collector to run and returns the total number of
 words of storage reclaimed. All of its arguments are optional: if they

-are not supplied, a call to GC simply causes a "copying" garbage
+are not supplied, a call to `GC` simply causes a "copying" garbage

 collection.
 
 If *min* is explicitly supplied as an argument, a garbage-collection
 parameter is changed permanently before the garbage collector runs.
 *min* is the smallest number of words of "free" (unclaimed, available
 for use) movable garbage-collected storage the garbage collector will
 collection.
 
 If *min* is explicitly supplied as an argument, a garbage-collection
 parameter is changed permanently before the garbage collector runs.
 *min* is the smallest number of words of "free" (unclaimed, available
 for use) movable garbage-collected storage the garbage collector will

-be satisfied with having after it is done. Initially it is 8192 words.
-If the total amount of reclaimed storage is less than *min*, the
-garbage collector will ask the operating system for enough storage (in
-1024 word blocks) to make it up. N.B.: the system may be incivil
-enough not to grant the request; in that case, the garbage collector
-will be content with what it has, **unless** that is not enough to
-satisfy a **pending** request for storage. Then it will inform you
-that it is losing. A large *min* will result in fewer total garbage
-collections, but they will take longer since the total quantity of
-storage to be dealt with will generally be larger. Smaller *min*s
-result in shorter, more frequent garbage collections.
+be satisfied with having after it is done each time. Initially it is
+8192 words.  If the total amount of reclaimed storage is less than
+*min*, the garbage collector will ask the operating system for enough
+storage (in 1024-word blocks) to make it up. N.B.: the system may be
+incivil enough not to grant the request; in that case, the garbage
+collector will be content with what it has, **unless** that is not
+enough to satisfy a **pending** request for storage. Then it will
+inform you that it is losing. A large *min* will result in fewer total
+garbage collections, but they will take longer since the total
+quantity of storage to be dealt with will generally be larger. Smaller
+*min*s result in shorter, more frequent garbage collections.
+
+*exh?* tells whether or not this garbage collection should be
+"exhaustive". It is optional, a `FALSE` by default. The difference
+between normal and exhaustive "copying" garbage collections is whether
+certain kinds of storage that require complicated treatment (for
+example, associations) are reclaimed. An exhaustive garbage collection
+occurs every eighth time that the "copying" algorithm is used, or when
+`GC` is called with this argument true, or when a normal garbage
+collection cannot satisfy the storage request.
+
+*ms-freq* gives the number of times the "mark-sweep" algorithm should
+be used hereafter for every time the normal "copying" algorithm is
+used. Giving `0` for *ms-freq* means never to use the "mark-sweep"
+algorithm, and giving `<CHTYPE <MIN> FIX>` means (effectively) always
+to use it. The "mark-sweep" algorithm uses considerably less processor
+time than the "copying" algorithm, but it never shrinks the
+free-storage pool, and in fact the pool can become fragmented. The
+"mark-sweep" algorithm could be useful in a program system (such as
+the compiler) where the size of the pool rarely changes, but objects
+are created and thrown away continuously.

 
 22.6. BLOAT
 -----------
 
 22.6. BLOAT
 -----------


@@ -8624,8 +8644,8 @@ by default), and indicate the following:
     `READ`ing large `STRING`s, and calling routines within the
     interpreter and compiled programs)
 
     `READ`ing large `STRING`s, and calling routines within the
     interpreter and compiled programs)
 

-Arguments on the second line are also `FIX` and optional, but they set
-garbage-collection parameters permanently, as follows:
+Arguments on the second line above are also `FIX` and optional, but
+they set garbage-collection parameters permanently, as follows:

 
 -   *min*: as for `GC`
 -   *plcl*: number of slots for `LVAL`s added when the space for
 
 -   *min*: as for `GC`
 -   *plcl*: number of slots for `LVAL`s added when the space for


@@ -8694,7 +8714,7 @@ about certain areas of storage. In detail:
 22.8. GC-MON
 ------------
 
 22.8. GC-MON
 ------------
 

-    <GC-MOND pred>
+    <GC-MON pred>

 
 ("garbage-collector monitor") determines whether or not the
 interpreter will hereafter print information on the terminal when a
 
 ("garbage-collector monitor") determines whether or not the
 interpreter will hereafter print information on the terminal when a


@@ -8720,7 +8740,7 @@ of `GIN` and `GOUT`.
 Two `SUBR`s, described next, use only part of the garbage-collector
 algorithm, in order to find all pointers to an object. `GC-DUMP` and
 `GC-READ`, as their names imply, also use part in order to translate
 Two `SUBR`s, described next, use only part of the garbage-collector
 algorithm, in order to find all pointers to an object. `GC-DUMP` and
 `GC-READ`, as their names imply, also use part in order to translate

-between Muddle objects and binary representation thereof.
+between Muddle objects and binary representations thereof.

 
 ### 22.9.1. SUBSTITUTE
 
 
 ### 22.9.1. SUBSTITUTE
 


@@ -8735,7 +8755,7 @@ the few legitimate uses for it is to substitute the "right" `ATOM` for
 the "wrong" one, after `OBLIST`s have been in the wrong state. This is
 more or less the way `ATOM`s are impurified. It is also useful for
 unlinking `RSUBR`s. `SUBSTITUTE` returns *old* as a favor: unless you
 the "wrong" one, after `OBLIST`s have been in the wrong state. This is
 more or less the way `ATOM`s are impurified. It is also useful for
 unlinking `RSUBR`s. `SUBSTITUTE` returns *old* as a favor: unless you

-hang onto *old* at that point, it will be garbage-collected.
+hang onto *old* at that point, it will be garbage.

 
 22.9.2 PURIFY
 -------------
 
 22.9.2 PURIFY
 -------------