Line numbers and GOTO

[Charles Pegge]

Eros may wish to avert his gaze.

http://community.thinbasic.com/index.php?topic=2517

LineNumbers1.tbasic
[code=thinbasic]

'LINE NUMBERS
'

uses "oxygen","file"
dim src as string

src = "
10 rem legacy
20 dim a,b,c,i
30 a=1 : b=1
40 c=a+b
60: i=i+1
70: if i<20 then a=b : b=c : goto 40 '
80:
80: print `FIBONACCI NUMBER: `+str$(c/b)
"




o2_basic src

'msgbox 0, o2_view "o2h "+src

if len(o2_error) then
msgbox 0, o2_error : stop
end if

o2_exec

'msgbox 0,o2_error

[/code]

[Charles Pegge]

This is a more palatable use of line numbers:

[code=thinbasic]
'
'LINE NUMBERS: CONTEMPORARY STYLE
'

uses "oxygen","file"
dim src as string

src = "

10:

dim a=1, b=1, c=0, i=0

20:

c=a+b
inc i
if i<20 then a=b : b=c : goto 20

30:

print `FIBONACCI NUMBER: ` str c/b

40:

"

o2_basic src
[/code]

[ErosOlmi]

Danger, danger !

[kryton9]

The first version looked fine to me and the code is tighter. Never saw a version like the second... it might grow on me so I won't be quick to judge.

Well the jmp command was just like a goto but with a label involved instead of line number in terms of a feature. I assume jmp is more efficient and is
not hated as much as goto?

I like line numbers as you know exactly where you are in the code. It is a feature I requested for thinAir and I know it will come in the future some time.
Without line numbers you have to always sort of analyze the code and it takes a few milliseconds to a couple of seconds depending on the code to know where you are when you scroll.

So thanks for adding them to the module!

[Charles Pegge]

GOTO translates to Assembly code jmp long in this instance. But Line numbers have to be turned into non-numbers internally. so all line numbers are prefixed with underscores _

To use JMP with line numbers it would be: jmp long _100 etc


When oxygegen reports an error it does not give the physical line number - instead it gives the last label encountered. Line numbers can be used as trace markers for this purpose - then removed in the final code.

[Michael Clease]

on the amiga I used to push my return address on the stack and do a JMP to a subroutine because it was quicker than a jsr would this still apply with 8086+ cpus?

[Charles Pegge]

Push return address and Jump is the operational equivalent of call - The slow parts are storing the return address to stack memory then refilling the instruction pipeline with code from a new memory location.

On today's 8086's Memory access time is the limiting factor.

What processor did your Amiga have? And was it doing any housekeeping prior to the call, which you might have been able to bypass?

[Michael Clease]

The Amiga used the 68000 range of CPUs and I cant remember what the code looked like its been about 10 years at least

[code=asm]
LEA returnaddress, (sp)+
JMP mysub[/code]

Timings

http://linas.org/mirrors/www.nvg.ntn...000timing.HTML

[Michael Hartlef]

The Amiga used the 68000 range of CPUs and I cant remember what the code looked like its been about 10 years at least

[code=asm]
LEA returnaddress, (sp)+
JMP mysub[/code]

Timings

http://linas.org/mirrors/www.nvg.ntn...000timing.HTML

Yes, that were the days. :P

[John Spikowski]

The first version looked fine to me and the code is tighter. Never saw a version like the second... it might grow on me so I won't be quick to judge.

In ScriptBasic, line numbers are labels and optional for compatibility. The numbering doesn't have to be in any order or used on every line.

100 FOR x = 1 TO 10
  PRINT x 
  GOSUB 50
NEXT x

END

50 PRINTNL
 RETURN