PFE 0.33.70

generated
(C) Guido U. Draheim
guidod@gmx.de

Environment

related definitions

---

ENVIRONMENT?( name-ptr name-len -- 0 | ?? name-flag! ) [ANS]  => [FORTH]

check the environment for a property, usually a condition like questioning the existance of specified wordset, but it can also return some implementation properties like "WORDLISTS" (the length of the search-order) or "#LOCALS" (the maximum number of locals)

Here it implements the environment queries as a SEARCH-WORDLIST in a user-visible vocabulary called ENVIRONMENT

  : ENVIRONMENT?
    ['] ENVIRONMENT >WORDLIST SEARCH-WORDLIST
    IF  EXECUTE TRUE ELSE  FALSE THEN ;
  

primitive code = [p4_environment_Q]

---

REQUIRED( ... str-ptr str-len -- ??? )  => [FORTH]

the filename argument is loaded via INCLUDED as an extension package to the current system. The filename is registered in the current ENVIRONMENT so that it is only INCLUDED once (!!) if called multiple times via REQUIRED or REQUIRES

primitive code = [p4_include_required]

---

REQUIRE( ... "file-name" -- ... )  => [FORTH]

parses the next WORD and passes it to REQUIRED this is the self-parsing version of REQUIRED and it does parrallel INCLUDE w.r.t. INCLUDED

primitive code = [p4_include_require]

---

NEEDS( name -- )  => [FORTH]

A self-parsing variant of an environment-query check. It is similar to a simulation like

 
  : NEEDS PARSE-WORD 2DUP ENVIRONMENT? 
    IF DROP ( extra value ) 2DROP ( success - be silent )
    ELSE TYPE ." not available " CR THEN ;
 

however that would only match those worset-envqueries which return a single extra item under the uppermost TRUE flag in the success case. Instead it works more like

 
  : NEEDS PARSE-WORD 2DUP ENVIRONMENT-WORDLIST SEARCH-WORDLIST
    IF 2DROP ( success - be silent and just drop the parsed word )
    ELSE TYPE ." not available " CR THEN ;
 

however we add the same extension as in ENVIRONMENT? as that it can automatically load a wordset module to fullfil a query that looks like "[wordsetname]-ext". Therefore, the following two lines are pretty much identical:

 
  LOADM floating
  NEEDS floating-ext
 

the difference between the two: if somebody did provide a forth level implementation of floating-ext then that implementation might have registered a hint "floating-ext" in the environment-wordlist. This extra-hint will inhibit loading of the binary module even if it exists and not been loaded so far. The LOADM however will not check the ENVIRONMENT-WORDLIST and only check its loadlist of binary wordset modules in the system.

It is therefore recommended to use NEEDS instead of LOADM unless you know you want the binary module, quickly and uncondtionally.

primitive code = [p4_needs_environment]