Being able to examine compiled code can help in identifying obscure bugs and gaining a deeper understanding of how things work. For this a decompiler is rather useful.
A simple binary dump is pretty easy:
````
:dump (an-)
[ fetch-next over putn putn chr:LF putc ] times drop ;
````
This can be useful, but the output doesn't help a lot. Consider an example:
The left column is the offset, the right is the stored value.
It'd be much more useful to map the stored values to instruction names. This is complicated by the fact that Nga allows for packing up to four instructions per cell. To decompile effectively we need a way to unpack them.
````
{{
:mask #255 and ;
:next #8 shift ;
:reorder (abcd-dcba)
rot push rot push swap pop pop swap ;
---reveal---
:unpack (n-dcba)
dup mask swap next
dup mask swap next
dup mask swap next
reorder ;
}}
````
With this I can then proceed to write a quick and dirty function that maps opcodes to a symbolic short name. As with the *Naje* assembler, I use two characters for each (this is sufficient to identify all of the Nga instructions).
The NOP instruction is represented by two periods (I do this for readability purposes). Unrecognized values are rendered as two question marks.
````
:name-instruction
#0 [ '.. ] case
#1 [ 'LI ] case
#2 [ 'DU ] case
#3 [ 'DR ] case
#4 [ 'SW ] case
#5 [ 'PU ] case
#6 [ 'PO ] case
#7 [ 'JU ] case
#8 [ 'CA ] case
#9 [ 'CC ] case
#10 [ 'RE ] case
#11 [ 'EQ ] case
#12 [ 'NE ] case
#13 [ 'LT ] case
#14 [ 'GT ] case
#15 [ 'FE ] case
#16 [ 'ST ] case
#17 [ 'AD ] case
#18 [ 'SU ] case
#19 [ 'MU ] case
#20 [ 'DI ] case
#21 [ 'AN ] case
#22 [ 'OR ] case
#23 [ 'XO ] case
#24 [ 'SH ] case
#25 [ 'ZR ] case
#26 [ 'EN ] case
drop '?? ;
````
