One kind of value
Many languages make you say whether a value is text or a number, and refuse to mix them. xTalk does not: every value can be read as text, and a value that looks like a number can be used as one. It works out what you mean from what you do with it.
put "5" + 3
put 10 & 5
put "3" * "4"
put "007" + 0
put empty + 58 105 12 7 5
+ wants numbers, so the text "5" is read as one. & wants text, so 10 and 5 are joined into 105. And empty, in a sum, counts as 0.
Asking what a value is
Because anything can be text, you often want to check that a value really is a number before you do sums with it: what someone typed into a field, say. is a asks:
put "12" is a number
put "twelve" is a number
put 3.5 is an integer
put "3.0" is an integer
put "true" is a boolean
put empty is a number
put "hello" is not a numbertrue false false true true false true
True and false
A comparison gives true or false, which are just the words "true" and "false". xTalk calls them booleans. You can keep one in a variable and use it later in an if.
put 3 > 2
put not (3 > 2)
put 10 > 20 into tIsBig
put tIsBig
put tIsBig is falsetrue false false true
Numbers compare as numbers
When both sides look like numbers, xTalk compares them as numbers, even when they are written differently. Otherwise it compares them as text, in alphabetical order, and without minding capital letters.
put "10" < "9"
put "10" = "10.0"
put "apple" < "banana"
put "Zebra" < "apple"false true true false
Try it yourself
Someone typed 42 into a form, and someone else typed forty. For each, put whether it is a number, and if it is, the number doubled.
Show a solution
put "42" into tFirst
put "forty" into tSecond
put tFirst is a number
put tFirst * 2
put tSecond is a numbertrue 84 false
Words in this lesson
Each one finds every lesson that uses it. The Dictionary has the whole story of each, with its syntax and more examples.