Liberty BASIC Family - User contributions [en]

Custom USING function (thousand separators)

2026-01-26T18:43:13Z

Tsh73: Created page with "{{Template:BuildingBlockLangImage}} == Description == :user-defined function <source lang="lb"> function using$(mask$, x) </source> :allows to add thousends separator, by including them im the mask. :"###,###,###.##" :Actually anything between # gets added to output, provided there are enough digits counting from the right. :(else it puts space instead, so whole length stays the same as mask) So it can do *"### ### ###.##" *"x=###,###,###.##$" and even *"(###)##-##-..."

{{Template:BuildingBlockLangImage}}

== Description ==
:user-defined function
<source lang="lb">
function using$(mask$, x)
</source>

:allows to add thousends separator, by including them im the mask.
:"###,###,###.##"
:Actually anything between # gets added to output, provided there are enough digits counting from the right.
:(else it puts space instead, so whole length stays the same as mask)

So it can do
*"### ### ###.##"
*"x=###,###,###.##$"

and even
*"(###)##-##-###"

:If you don't need extra spaces from the left, use TRIM$() like this
:trim$(using$(mask$, x))

<source lang="lb">
randomize .5

print "String";tab(15);"Val";tab(30);"Using";tab(50);"using$"
for i = 1 to 20
n = int(rnd(1)*10)
a$=""
for j = 1 to n
a$=a$;int(rnd(1)*10)
next
a$=a$;"."
for j = 1 to 3
a$=a$;int(rnd(1)*10)
next
if rnd(1)<0.5 then a$="-";a$
a=val(a$)
print a$;tab(15);a;tab(30);using("############.##", a);tab(50);using$("###,###,###,###.##", a)
next

print
print "Also can do:"
x=1234567.8901
mask$ = "###,###,###.##"
print x, ">";mask$;"<", ">";using$(mask$, x);"<"
mask$ = "x=###,###,###.##$"
print x, ">";mask$;"<", ">";using$(mask$, x);"<"
mask$ = "any text ###,###,###.## more"
print x, ">";mask$;"<", ">";using$(mask$, x);"<"
mask$ = "### ###,###.##"
print x, ">";mask$;"<", ">";using$(mask$, x);"<"
mask$ = "### ### ###.##"
print x, ">";mask$;"<", ">";using$(mask$, x);"<"

function using$(mask$, x)
delim1000$ = "," 'the point is, we do not print them (print " ") if there are no digit in this place

realMask$ = ""
for i = 1 to len(mask$)
c$=mid$(mask$,i,1)
if instr("#.", c$) then realMask$ = realMask$ + c$
next

x$=using(realMask$, x)
'print x$

xx$=""
j = 1
digitStarted=0
for i = 1 to len(mask$)
c$=mid$(mask$,i,1)
if instr("#.", c$) then
cc$=mid$(x$,j,1)
xx$ = xx$ + cc$
j=j+1
digitStarted = (instr(" -", cc$)=0)
else
if instr(delim1000$, c$) then
if digitStarted = 0 then
if cc$="-" then 'if we have " -," we should convert it to " -"
xx$ = left$(xx$, len(xx$)-1) + " "
c$="-"
else
c$=" " 'skip thousand delimiter if digits not started yet
end if
end if
end if
xx$ = xx$ + c$
end if
next
using$ = xx$
end function
</source>

[[Category:Liberty BASIC]]
[[Category:Just BASIC]]
[[Category:Building Blocks]]

The MAINWIN command changes the preferences of the IDE

2023-12-30T10:00:30Z

Tsh73:

==Description==
If one is using the MAINWIN command, the preferences of the mainwin size in the setup dialog get overwritten.
This leads to a persistent change, which is not expected by the user.

==Example code to demonstrate the bug.==
<source lang="lb">
MAINWIN 100 40
</source>

==Example code to work around the bug.==
<source lang="lb">
'do not use the MAINWIN command
'OR if you REALLY need it done, warn user first
</source>

[[Category:Bug Tracker]]

Floating point maths

2023-12-30T09:55:56Z

Tsh73:

==Description==
Due to the [http://en.wikipedia.org/wiki/Floating_point#Accuracy_problems Floating Point Error] of the mathematical co-processor in your computer you will not be able to sum or compare a floating point variable to an "exact" amount. There is always a tiny little difference. This is not unique to Liberty, all programs have to deal with this.

Liberty keeps two types of numbers, integers, which have nothing after the decimal point and floats, which have an amount after the decimal point. If you see 2 listed you can be sure it is held as an integer. If you see 2.0 listed it is held as a float and there is a tiny amount after the decimal. Floats are held to 16 decimal places, right click in the debugger and click on the option to view the full number. Most often floats are truncated for display.

==Example 1==

===Example code to demonstrate the bug.===
<source lang="lb">
a = 2.1 - 2
b = 0.1
print
print a, b
print
print "(2.1 - 2) = 0.1 (should print 1 (True)) ... "; a = b
print
print using("#.################################", a)
print using("#.################################", b)
</source>

===Example code to work around the bug.===
<source lang="lb">
a = 2.1 - 2
b = 0.1
precision = 1e-16
print
print a, b, precision
print
print "(2.1 - 2) = 0.1 (should print 1 (True)) ... "; abs(a - b) < precision
print
print using("#.################################", a)
print using("#.################################", b)
</source>
You should '''never''' try to compare floating point numbers for being equal. If you must, compare them to a level of precision as shown.
1e-16 is the narrowest of margins, you might choose 1e-7 to allow a wider margin of error. Better still, don't try and compare floats, use integers.

==Example 2==

===Example code to demonstrate the bug.===
<source lang="lb">
for i = 1 to 2 step 0.1
print i
next
</source>
Expected result:
: printed numbers from 1 to 2 with step 0.1
What actually happens:
: printed numbers from 1 to 1.9 with step 0.1

===Example code to work around the bug.===
<source lang="lb">
for i = 0 to 10
num = 1 + i * 0.1
print num
next
</source>
Looping using integer numbers provides an exact number of steps.

[[Category:Bug Tracker]]
[[Category:NoBug Bug Reports]]

Floating point maths

2023-12-30T09:54:54Z

Tsh73:

Jumping out of a nested FOR loop gives unexpected results

2023-11-22T20:47:00Z

Tsh73:

==Description==
Jumping out of a FOR loop is bad practice because it causes a memory leak, but in the case of nested loops it can also give strange results. Specifically, the loop variable seems not to be reset to the initial value when the FOR is executed again.

==Example code to demonstrate the bug.==
<source lang="lb">
for y = 1 to 3
for x = 1 to 5
if x = 4 then goto [skip]
print x, y
next x
[skip]
next y
</source>

The expected output from this program is:
<pre>1 1
2 1
3 1
1 2
2 2
3 2
1 3
2 3
3 3
</pre>
but the actual output is:
<pre>1 1
2 1
3 1
5 1
1 2
2 2
3 2
5 2
1 3
2 3
3 3
5 3
</pre>
One would not expect '''x''' ever to have the value '''5'''!

==Example code to work around the bug.==
Use EXIT FOR. It is explicitely stated in a help file, '''"FOR..NEXT" \ Exiting a loop prematurely''':

''GOTO should not be used to exit a FOR/NEXTloop. "EXIT FOR" will correctly exit the loop before it would have terminated normally. ''
<source lang="lb">
for y = 1 to 3
for x = 1 to 5
if x = 4 then exit for
print x, y
next x
next y
</source>

== Related bugs==
You can get same behavoiour with other kinds of loops
(DO / LOOP, WHILE / WEND).

EXIT DO, EXIT WHILE saves the day, as well.

== Other versions of Liberty BASIC==
This 'bug' does not exist in Liberty BASIC 5 or in Run BASIC. You can jump out of a FOR/NEXT loop in those versions without issues.

[[Category:Bug Tracker]]
[[Category:NoBug Bug Reports]]