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U<

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powersoft_51

Post subject: U<

Posted: Mon Jul 29, 2024 3:23 pm

Joined: Sat Jun 22, 2024 6:21 am
Posts: 14

I have some trouble with the implemented U< in my figforth for the 6502.
For example :
$7FFF $D800 U< true
$4000 $D800 U< true
$0400 $D800 U< false
$E000 $D800 U< false

The code is :

Code:

1472   0C0E             ;                                       U<
1473   0C0E             ;                                       Unsigned less than
1474   0C0E             ;
1475   0C0E 82 55 BC    L1246     .BYTE $82,"U",$BC
1476   0C11 02 0C                       .WORD L1244    ; link to =
1477   0C13 D6 09       ULESS      .WORD DOCOL
1478   0C15 FA 0B                       .WORD SUB      ; subtract two values
1479   0C17 88 08                       .WORD ZLESS    ; test sign
1480   0C19 0C 08                       .WORD SEMIS

Is there a better code to do this comparision/

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GARTHWILSON

Post subject: Re: U<

Posted: Mon Jul 29, 2024 6:08 pm

Joined: Fri Aug 30, 2002 1:09 am
Posts: 8539
Location: Southern California

I have it as a primitive:

Code:

    LDA  3,X
    CMP  1,X
    BNE  1$

    LDA  2,X
    CMP  0,X
1$: BCS  2$
    JMP  POP-TRUE

2$: JMP  POP-FALSE

_________________
http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

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JimBoyd

Post subject: Re: U<

Posted: Tue Jul 30, 2024 8:00 pm

Joined: Fri May 05, 2017 9:27 pm
Posts: 895

So do I.

Code:

CODE U< ( N1 N2 -- F )
   2 ,X LDA  0 ,X CMP
   3 ,X LDA  1 ,X SBC
   CS NOT IF  DEY  THEN
   LABEL FLAG.POP
   2 ,X STY  3 ,X STY
   POP JMP  END-CODE

Note: Other primitives in the kernel source use the label FLAG.POP as a branch or jump destination.

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