Forth Programmer’s Handbook
\Rates are used as offsets into arrays 0 CELLS CONSTANT FULL
1 CELLS CONSTANT LOWER
2 CELLS CONSTANT LOWEST
\Array-defining word
: FOR CREATE DOES> ( rate - charge-per-minute) + @ ;
\Table comprises three arrays
\Charge-per-minute at FULL LOWER LOWEST rate
FOR FIRST |
30 |
, |
22 |
, |
12 |
, |
|
FOR |
+MINUTES |
20 |
, |
15 |
, |
9 |
, |
FOR |
DISTANCE |
12 |
, |
10 |
, |
6 |
, |
90 CONSTANT ASSISTANCE |
\ Charge |
for |
operator assistance |
||||
: ?ASSISTANCE |
( flag - |
charge) |
ASSISTANCE AND ; |
||||
: ADDITIONAL |
( #minutes-1 rate - |
charge) |
+MINUTES * ; |
||||
: MINUTES |
( #minutes rate - |
charge) |
|
|
|||
DUP FIRST |
ROT 1- ROT |
ADDITIONAL |
+ ; |
|
|||
: MILES |
( distance #minutes |
rate |
- charge) |
DISTANCE * * ; |
|||
: TOTAL |
( distance #minutes |
rate |
assistance-flag - charge) |
||||
?ASSISTANCE >R 2DUP |
MINUTES >R |
MILES |
2R> + + ; |
||||
Stack music. Unreadable?
Rule:
9. Feature the stack machine.
6.3.7 Summary
How do we feel about these rules? Are any of them helpful? Hurtful? Are there better rules? Do we want rules anyway? These are questions for you to answer, should you so choose.
6.4 NAMING CONVENTIONS
Table 10 presents some naming conventions that have been widely used in Forth for many years. These take advantage of Forth’s flexible naming rules to use special characters to convey additional meaning.
In this table, the word name refers to some word the programmer has chosen to
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Forth Programmer’s Handbook
represent a Forth routine.
Where possible, a prefix before a name indicates the type or precision of the
!value being operated on, whereas a suffix after a name indicates what the value is or where it’s kept.
Table 10: Naming conventions
Prefixes |
Meaning |
Examples |
!name |
Store into name |
!DATA |
#name |
Size or quantity |
#PIXELS |
|
Output numeric operator |
#S |
|
Buffer name |
#I |
'name |
Address of name |
'S |
|
Address of pointer to name |
'TYPE |
(name) |
Internal component of name, not normally |
(IF) |
|
user-accessible |
(FIND) |
|
Run-time procedure of name |
(:) |
|
File index |
(PEOPLE) |
*name |
Multiplication |
*DIGIT |
|
Takes scaled input parameter |
*DRAW |
+name |
Addition |
+LOOP |
|
Advance |
+BUF |
|
Enable |
+CLOCK |
|
More powerful |
+INITIALIZE |
|
Takes relative input parameters |
+DRAW |
-name |
Subtract, remove |
-TRAILING |
|
Disable |
-CLOCK |
|
not name (opposite of name) |
-DONE |
|
Returns reversed truth flag |
-MATCH |
|
(1 is false, 0 is true) |
|
|
Pointers, especially in files |
-JOB |
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Forth Programmer’s Handbook |
|
Table 10: |
Naming conventions (continued) |
|
|
|
|
Prefixes |
Meaning |
Examples |
.name |
Print named item |
.S |
|
Print from stack in named format |
.R .$ |
|
Print following string |
." string" |
|
May be further prefixed with data type |
D. U. U.R |
/name |
Division |
/DIGIT |
|
Initialize routine or device |
/COUNTER |
|
“per” |
/SIDE |
1name |
First item of a group |
1SWITCH |
|
Integer 1 |
1+ |
|
One-byte size |
1@ |
2name |
Second item of a group |
2SWITCH |
|
Integer 2 |
2/ |
|
Two-cell size |
2@ |
;name |
End of something |
;S |
|
End of something, start of something else |
;CODE |
<name |
Less than |
<LIMIT |
|
Open bracket |
<# |
|
From device name |
<TAPE |
<name> |
Name of an internal part of a device driver |
<TYPE> |
|
routine |
|
>name |
Towards name |
>R, >TAPE |
|
Index pointer |
>IN |
|
Exchange, especially bytes |
>< (swap bytes) |
|
|
>MOVE< (move, |
|
|
swapping bytes) |
?name |
Check condition, return true if yes |
?TERMINAL |
|
Conditional operator |
?DUP |
|
Check condition, abort if bad |
?STACK |
|
Fetch contents of name and display |
?N |
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Forth Programmer’s Handbook
Table 10: |
Naming conventions (continued) |
|
|
|
|
Prefixes |
Meaning |
Examples |
@name |
Fetch from name |
@INDEX |
Cname |
One-byte character size, integer |
C@ |
Dname |
Double-cell integer |
D+ |
Mname |
Mixed single and double operator |
M* |
Tname |
Three-cell size |
T* |
Uname |
Unsigned encoding |
U. |
[name] |
Executes at compile time |
['] |
\name |
Unsigned subtraction (ramp-down) |
\LOOP |
name! |
Store into name |
B! |
name" |
String follows, delimited by " |
ABORT" xxx" |
name, |
Put something into dictionary |
C, |
name: |
Start definition |
CASE: |
name> |
Close bracket |
#> |
|
Away from name |
R> |
name? |
Same as ?name |
B? |
name@ |
Fetch from name |
B@ |
200 Programming Style