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DB006 G144A12 polyFORTH Supplement
NEXT C( a)
Ends a loop that tests the top of the return stack. If nonzero, the value is decremented by 1
and a jump is made to the address given during compilation. If zero, the value is discarded from the
return stack and execution continues. 3 FOR I . NEXT displays 3 2 1 0 .
4.3.4 Compiler Internals
Active compilers require a few additional functions. Here are relevant compiler control functions:
STATE
is a USER variable controlling the dictionary search. If 1, we are compiling and the dictionary
search checks each IMMEDIATE subvocabulary before it checks the corresponding normal
vocabulary. Otherwise it is zero and we ignore the IMMEDIATE subvocabularies. STATE is
maintained automatically by the compiler.
IMM
is a system variable whose value is odd immediately following a dictionary search if an IMMEDIATE
word was found. Note that this value may be changed after a PAUSE .
IMMEDIATE
is used after semicolon to move the most recently created definition to the current
IMMEDIATE subvocabulary.
compiles a call to the following word even if that word is IMMEDIATE .
[COMPILE] (_)
\ ( _)
is shorthand for [COMPILE] .
LITERAL ( n)
stack.
an IMMEDIATE word that compiles a literal whose value is taken from the compiler's
RECURSIVE
is an IMMEDIATE word; used inside a definition to un-smudge the name of that definition so
it is findable.
The following internal functions are useful when extending the compiler; the optimization capability has not proven
useful and will probably be deprecated soon:
uCODE ( n _) defines a new VM instruction with the value n . It's visible in the regular compiler so that
you may name new instructions if you choose to customize the Virtual Machine.
-COMPILE
sets STATE to zero.
,C
compiles a VM instruction and marks it as optimizable.
a,
compiles an address and marks it not optimizable.
-CODE
\\
indicates that there is no optimizable instruction.
is shorthand for -CODE .
Functions present on some polyFORTH systems but omitted here: 2LITERAL
4.3.5 Missing Interpretables
In this release, the following primitives are only available in compilation forms.
2+
26
2-
EXECUTE
BYTE
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