Find limit of recursion: Difference between revisions
Add Uxntal
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recurse 1</syntaxhighlight>
=={{header|Uxntal}}==
Uxn has a known stack size of 256 bytes, which allows 128 function calls. However, assuming we don’t know this, we can find the stack size with a program anyway. In older versions of Uxn, it was possible to detect stack overflow with the System vector, which would make this task easier, but the current Uxn stacks are circular, with no overflow and underflow checks, which means that we have to get a bit more creative. Calling a recursive function enough times will cause the return stack pointer to wrap around and overwrite the first return address, which means execution will be trapped in the recursive function forever. By detecting when the function has run more times than expected, the recursion limit can be found.
<syntaxhighlight lang="Uxntal">|00 @System &vector $2 &expansion $2 &wst $1 &rst $1 &metadata $2 &r $2 &g $2 &b $2 &debug $1 &state $1
|10 @Console &vector $2 &read $1 &pad $4 &type $1 &write $1 &error $1
|00 @calls $1
|0100
#01
&loop
DUP .calls STZ
recurse
INC !&loop
@recurse
( keep calling recurse until stack value is 00 )
#01 SUB DUP #00 EQU ?&done
recurse
( as we walk back up the stack, increment counter )
&done INC
( if we go above the original call count, the stack was corrupted )
DUP .calls LDZ GTH ?&fail
JMP2r
&fail
;msg1 print-str
.calls LDZ print-hex
;msg2 print-str
#80 .System/state DEO BRK
@print-str
&loop
LDAk .Console/write DEO
INC2 LDAk ?&loop
POP2
JMP2r
@print-hex
DUP #04 SFT print-digit #0f AND print-digit
JMP2r
@print-digit
DUP #09 GTH #27 MUL ADD #30 ADD .Console/write DEO
JMP2r
@msg1 "Stack 20 "overflow 20 "at 20 "# 00
@msg2 20 "calls. 0a00</syntaxhighlight>
=={{header|Vala}}==
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