Digest #249 2024-01-06


[328] 2024-01-05 08:52:21 lmr wrote:

requestClarification - throw code for compiling outside a definition

Based on previous comments it's quite clear that both LITERAL and COMPILE, should to check at runtime whether they are appending to an existing definition, or (as GForth puts it) "compiling outside a definition". Merely disallowing their usage in @ STATE zero is not enough. But I'm wondering, if the system detects an attempt to append to a non-existing definition, what would be the most appropriate error code? -14 (interpreting a compile-only word)? -9 (invalid address)?

[329] 2024-01-05 17:07:09 lmr wrote:

requestClarification - are colon-defs supposed to be compiled in data space?

This may be very basic, but: are colon-definitions supposed to be compiled in data space (addressable by @, ! etc)? Can the thread of compiled XTs (or whatever the implementation uses) for a definition reside in some other address space, visible only to the inner interpreter or the equivalent? I suppose the answer is obvious, since presumably an implementation could compile everything to a primitive.


[r1164] 2024-01-01 07:56:56 AntonErtl replies:

requestClarification - diff from CORE FIND?

The difference is that the search order version contains the following words, but the core version does not:

after searching all the word lists in the search order

[r1165] 2024-01-01 09:50:56 AntonErtl replies:

proposal - CS-DROP (revised 2019-08-22)

Concerning the interaction of the extension of cs-pick and the introduction of cs-drop with automatic scoping (a Gforth feature), it does not pose any difficulties that were not there before. However, these features may increase the probability that users run into these (up-to-now extremely rare) difficulties.

Here's the case analysis for it:

For dests there is nothing new for cs-pick. In the usual case when the begin that produced the dest is reachable from above, Cs-drop results in the same situation that one would have if one had written the code without the begin. In the case when the begin is unreachable from above, it results in the same situation one would have if the begin was immediately followed by again or until: the locals visible after the begin are only those visible at the latest place outside any control structure.

For origs, whatever cs-picks and cs-drops are used, eventually the orig is resolved by a then, and the situation for automatic scoping does not change compared to the case when the same code had been written without cs-pick and cs-drop.

The reason why these words do not change the situation is because automatic scoping does not work with control-flow stack items except when they are resolved by then, until, or again, or when the programmer uses assume-live.

[r1166] 2024-01-05 09:27:20 lmr replies:

referenceImplementation - Implementing COMPILE, via EXECUTE

: compile, ( xt -- ) postpone literal postpone execute ; It's not an efficient implementation, but a correct and portable one.

The postpone execute part above needs to append execute's XT to the current definition, i.e. a COMPILE, itself