Functions
`fastn` supports functions which users can create to execute their own logic
in their `fastn` documents. It also provides various
[`built-in-functions`](/built-in-functions/)
which users can use anywhere in their `fastn` document.
How to create functions?
To create a function, you need to follow the function declaration syntax which
is as follows:
Function Declaration syntax
-- <return-type> <function-name>(<arg-1-name>, <arg-2-name>, ...):
<arg-1-type> <arg-1-name>: <optional-default-value>
<arg-2-type> <arg-2-name>: <optional-default-value>
...
<function-body>
Lang:
ftd
Using the above declaration syntax, a simple `add()` function
is defined below which takes two integer as arguments
and returns the added value.
Sample `add()` function
-- integer add(a, b):
integer a:
integer b:
a + b
Lang:
ftd
How to use your functions ?
Once functions have been defined, you can use these functions by invoking it
by using `$`.
Sample code using add() function
Input
-- integer add(a, b):
integer a:
integer b:
a + b
-- ftd.column:
spacing.fixed.px: 10
color: $inherited.colors.text
-- ftd.text: Adding 35 and 83
-- ftd.integer: $add(a=35, b=83)
-- end: ftd.column
Lang:
ftd
Output
Adding 35 and 83
118
Some frequently used functions
Below mentioned are some of the most frequently used functions which can be
created as per the requirement and are not part of `fastn`.
Clamp
Clamp functions are used to limit your given value between certain range.
Regular Clamp
This function will clamp the value between 0 and `max`.
Value will range from `[0,max]` given `max > 0`.
Sample code using `regular-clamp()`
Input
-- integer $num: 0
-- display-integer: $num
$on-click$: $regular-clamp($a = $num, by = 1, max = 6)
-- void regular-clamp(a,by,max):
integer $a:
integer by:
integer max:
a = (a + by) % (max + 1)
Lang:
ftd
Output
0
Clamp with min and max
This function will clamp the value between `min` and `max`.
Value will range from `[min,max]` given `max > min`.
Sample code using `clamp_with_limits()`
Input
-- integer $n: 1
-- display-integer: $n
$on-click$: $clamp_with_limits($a = $n, by = 1, min = 1, max = 6)
-- void clamp_with_limits(a,by,min,max):
integer $a:
integer by: 1
integer min: 0
integer max: 5
a = (((a - min) + by) % (max + 1 - min)) + min
Lang:
ftd
Output
1
