Formatting text and numbers · Lessons

How many decimals?

When xTalk turns a number into text, to show it or put it in a field, it uses the numberFormat: up to six decimals unless you say otherwise. Set it to a pattern of 0 (always show a digit) and # (show a digit only if needed):

ExampleRun it in the playground

put 22 / 7
set the numberFormat to "0.00"
put 22 / 7
put 2 + 0
set the numberFormat to "0.###"
put 22 / 7
put 2.5 + 0

Output

The numberFormat changes only how a number becomes text. The number itself keeps all its precision:

ExampleRun it in the playground

set the numberFormat to "0.0"
put 1 / 3 into tThird
put tThird
set the numberFormat to "0.######"
put tThird * 3

Output

0.3
1

Rounding

round rounds to the nearest whole number, or to as many decimals as you ask. Halves go away from zero. A negative number of places rounds to tens, hundreds and so on. trunc just cuts the decimals off.

ExampleRun it in the playground

put round(2.5) && round(3.5) && round(-2.5)
put round(3.14159, 2)
put round(1234.5, -2)
put trunc(-3.7) && trunc(3.7)

Output

Fill in the blanks: format

format builds text from a template, like printf in C. Each % code in the template is replaced by the next value: %d a whole number, %f a number with decimals, %s text, %x a number in hexadecimal.

ExampleRun it in the playground

put format("%d items at %.2f each", 3, 4.5)
put format("%s is %d years old", "Ada", 36)
put format("%05d", 42)
put format("%x in hex is %X", 255, 255)
put format("100%%")

Output

3 items at 4.50 each
Ada is 36 years old
00042
ff in hex is FF
100%

A number between % and the letter is a width, which pads the value with spaces; a minus sign pads on the right instead of the left. That is how to line up columns in plain text:

ExampleRun it in the playground

put "Ada,36.5" & return & "Grace,112" & return & "Linus,7.25" into tRows
repeat for each line tRow in tRows
   put format("%-8s|%8.2f", item 1 of tRow, item 2 of tRow)
end repeat

Output

Ada     |   36.50
Grace   |  112.00
Linus   |    7.25

format also turns \n into a new line and \t into a tab, so it is a compact way to write those inside a string.

Thousands separators

There is no built-in pattern for 1,234,567, but a short function does it, and shows chunk expressions at work:

ExampleRun it in the playground

function withCommas pNumber
   put trunc(pNumber) into tWhole
   put empty into tOut
   repeat while the length of tWhole > 3
      put comma & char -3 to -1 of tWhole before tOut
      delete char -3 to -1 of tWhole
   end repeat
   return tWhole & tOut
end withCommas

put withCommas(1234567)
put withCommas(999)
put withCommas(1000)

Output

1,234,567
999
1,000

Templates: merge

merge fills a template with the values of expressions written between double square brackets. It is the easiest way to build a long piece of text, an email or a web page, with values in it:

ExampleRun it in the playground

put "Ada" into tName
put 36 into tAge
put merge("Hello [[tName]], next year you will be [[tAge + 1]].")
put merge("[[toUpper(tName)]] has [[the length of tName]] letters.")

Output

Hello Ada, next year you will be 37.
ADA has 3 letters.

Try it yourself

Print a receipt: for each line of Tea,2,1.8, Cake,1,3.25 and Juice,3,2 (name, quantity, price), put the name padded to 8 characters, the quantity, and the line's total with two decimals, then a total line.

Show a solution

ExampleRun it in the playground

put "Tea,2,1.8" & return & "Cake,1,3.25" & return & "Juice,3,2" into tOrder
put 0 into tTotal
repeat for each line tLine in tOrder
   put item 2 of tLine * item 3 of tLine into tCost
   add tCost to tTotal
   put format("%-8s x%d %7.2f", item 1 of tLine, item 2 of tLine, tCost)
end repeat
put format("%-11s %7.2f", "Total", tTotal)

Output

Tea      x2    3.60
Cake     x1    3.25
Juice    x3    6.00
Total         12.85

Words in this lesson

formatnumberFormatroundtruncmerge%d%s%f

Each one finds every lesson that uses it. The Dictionary has the whole story of each, with its syntax and more examples.