Floor/Ceil

[Peter]

Deleted...

[Charles Pegge]

Hi Peter,
Try these. If they are okay, I will add them to the maths library.

Code: OxygenBasic

1.  
2. double a,b
3.  
4. a=2.4
5. b=-2.7
6.  
7.  
8. deff floor
9. '=========
10. sub esp,8 : fstcw [esp] : fstcw [esp+2] : or [esp],0xc00
11. fldz
12. fcomip st0
13. (
14.   jae exit
15.   fchs
16. )
17. frndint
18. (
19.   jae exit
20.   fchs
21. )
22. fldcw [esp+2] : add esp,8
23. end deff
24.  
25.  
26. deff ceil
27. '========
28. fld st0
29. frndint
30. (
31.   fcomip st1
32.   jz exit
33.   fldz
34.   sub esp,8 : fstcw [esp] : fstcw [esp+2] : or [esp],0xc00
35.   fcomip st0
36.   (
37.     jae exit
38.     fchs
39.   )
40.   fld1
41.   faddp st1
42.   frndint
43.   (
44.     jae exit
45.     fchs
46.   )
47.   fldcw [esp+2] : add esp,8
48. )
49. end deff
50.  
51.  
52.  
53. print floor(a) "   " ceil(a)
54. print floor(b) "   " ceil(b)
55.  

Charles

[Charles Pegge]

Tricky little devils.

I think these will do it:

Code: OxygenBasic

1.  
2. double a,b
3.  
4. a=2.4
5. b=-2.7
6.  
7.  
8. deff floor
9. '=========
10. fld st0
11. frndint
12. (
13.   fcomip st1
14.   jz exit
15.   sub esp,8 : fstcw [esp] : fstcw [esp+2] : or [esp],0xc00
16.   fldcw [esp]
17.   fldz
18.   fcomip st1
19.   (
20.     jbe exit
21.     fchs
22.     fld1
23.     faddp st1
24.   )
25.   frndint
26.   (
27.     jbe exit
28.     fchs
29.   )
30.   fldcw [esp+2] : add esp,8
31. )
32. end deff
33.  
34.  
35. deff ceil
36. '========
37. fld st0
38. frndint
39. (
40.   fcomip st1
41.   jz exit
42.   fldz
43.   sub esp,8 : fstcw [esp] : fstcw [esp+4] : or [esp],0xc00
44.   fldcw [esp]
45.   fcomip st1
46.   (
47.     jbe exit
48.     fchs
49.     jmp fwd nfld1
50.   )
51.   fld1
52.   faddp st1
53.   .nfld1
54.   '
55.  frndint
56.   (
57.     jbe exit
58.     fchs
59.   )
60.   fldcw [esp+4] : add esp,8
61. )
62. end deff
63.  
64. 'sign sensitive
65.  
66.  
67. 'print floor(a) "   " ceil(a)
68. 'print floor(b) "   " ceil(b)
69.  
70. print floor  2.3  ' 2.0   round down
71. print floor -2.3  '-3.0   round down
72.  
73. print ceil  2.7  ' 3.0    round up
74. print ceil -2.7  '-2.0    round up
75.  
76.  

Charles

[Charles Pegge]

My reference is Wikipedia

http://en.wikipedia.org/wiki/Floor_and_ceiling_functions

And the code is based upon the trunc deff.

The FPU control word stuff causes unconditional rounding-down.

Charles

[Charles Pegge]

Better solution:

http://webster.cs.ucr.edu/AoA/Windows/HTML/RealArithmetic.html

Code: OxygenBasic

1.  
2. 'http://webster.cs.ucr.edu/AoA/Windows/HTML/RealArithmetic.html
3.  
4. deff floor
5. '=========
6. sub esp,8
7. fstcw [esp] : fstcw [esp+4] : and [esp],0xf3ff : or [esp],0x0400 'round down
8. fldcw [esp]
9. frndint
10. fldcw [esp+4]
11. add esp,8
12. end deff
13.  
14. deff ceil
15. '=========
16. sub esp,8
17. fstcw [esp] : fstcw [esp+4] : and [esp],0xf3ff : or [esp],0x0800 'round up
18. fldcw [esp]
19. frndint
20. fldcw [esp+4]
21. add esp,8
22. end deff
23.  
24. print floor 7.5
25. print floor -7.5
26. print ceil 7.5
27. print ceil -7.5
28.  

Charles