decimal point

[ds123]

In Sinclair BASIC how do i display a number to two decimal points?

eg' 13.52

[ParadigmShifter]

PRINT INT(x * 100)/100

or

PRINT INT(x * 100 + 0.5)/100

if you want rounding

Here's a function version which takes the number of significant digits s as second parameter

DEF FN r(x,s)=INT(x*(10^s)+0.5)/(10^s)

It's slow and I can't remember how many significant digits the 5 byte floats have in Basic are but I wouldn't use more than 5 and expect accurate results I think. Can probably speed it up using a subroutine but you couldn't pass local parameters to that (but you would only evaluate 10^s once then to speed it up)

If you want fixed width numbers so 1.234 and 12.34 say (both same width, 5 including the decimal point), you would use STR$ to convert a number into a string then do stuff with that based on the length (probably have to turn it into scientific notation if it was too wide?) Or you could use logarithms which would be a lot slower

[1024MAK]

Convert it to a string and then use the string slicing to chop off the bit you don’t want.

Mark

[ParadigmShifter]

Yeah I suggested something like that in my edit (use STR$).

You can't round easily doing that and if you have to search for the decimal point it will probably be slower? Both methods have issues if the number would be displayed in scientific notation. But you can pad numbers with no decimal point so they show zeroes that way too (so 1 -> 1.00). Fixed width strings have a length issue with negative numbers too (probably want to pad positive numbers with a leading space then) so you would get output like this

Code: Select all

 12.34
-45.67

If you use one of the modern basic compilers on the PC that produce compiled code that will run on the spectrum they will most likely have a function which will do much better string formatting.

[ParadigmShifter]

Another thing you can do if the numbers represent currency (or something which should never be rounded) is store the value * 100 and do this



Or a version which builds a string in a$ and has currency symbol in c$, pads non negative amounts with a leading space, and an example of how to print something right justified (you have to watch that the width is actually less than or equal to the specified width though). Also probably want to pad with spaces at the beginning so it would also work if the money was counting down instead.