This commit is contained in:
Brad Nelson
2021-01-22 22:43:52 -08:00
parent 2d584832cb
commit 39840858d7
2 changed files with 8 additions and 30 deletions

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@ -1,33 +1,13 @@
# The many faces of EForth
# EForth
EForth is a delightfully minimalist approach to Forth originated by Bill Muench and Dr. C. H. Ting.
In its original form metacompilation is avoided.
For more information visit:
[https://eforth.appspot.com/](https://eforth.appspot.com/)
## Directories
* reference/ - EForth Reference Material
* ueforth/ - µEforth - EForth refactored to allow source boostraping.
* circleforth/ - A minimalist Forth modeled after toy Lisps.
* ueforth/ - micro EForth - EForth refactored to allow source boostraping.
## EForth Quirks
EForth uses `FOR..NEXT` in favor of `DO..LOOP`:
[FOR/NEXT](https://github.com/TG9541/stm8ef/wiki/eForth-FOR-..-NEXT).
This construct has the odd property that it iterates one "extra" time for zero.
```
: FOO 10 FOR R@ . NEXT ; FOO
10 9 8 7 6 5 4 3 2 1 0 ok
```
To permit a more ordinary loop the `AFT` word is used in the sequence `FOR..AFT..THEN..NEXT`.
```
: FOO 10 FOR ( 1st time only ) AFT R@ . THEN NEXT ; FOO
9 8 7 6 5 4 3 2 1 0 ok
```
The even more enigmatic `FOR..WHILE..NEXT..ELSE..THEN` is used in place of `DO..LEAVE..LOOP`.
It allows a while condition to early out of a counted loop.
* reference/ - EForth Reference Material

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@ -16,16 +16,14 @@ typedef uintptr_t ucell_t;
#ifndef SSMOD_FUNC
# if __SIZEOF_POINTER__ == 8
typedef __int128_t dcell_t;
typedef __uint128_t udcell_t;
# elif __SIZEOF_POINTER__ == 4 || defined(_M_IX86)
typedef int64_t dcell_t;
typedef uint64_t udcell_t;
# else
# error "unsupported cell size"
# endif
# define SSMOD_FUNC dcell_t d = (dcell_t) *sp * (dcell_t) sp[-1]; \
--sp; *sp = (cell_t) (((udcell_t) d) % tos); \
tos = (cell_t) (d < 0 ? ~(~d / tos) : d / tos)
--sp; cell_t a = (cell_t) (d < 0 ? ~(~d / tos) : d / tos); \
*sp = (cell_t) (d - ((dcell_t) a) * tos); tos = a
#endif
#define OPCODE_LIST \