Built-in library

Every Swan program starts with these names already bound:

In a template, the engine also binds texl, which imports other documents, and the host can bind its own names (see Names and data).

Reading the reference

Each entry starts with a signature that shows how to call the function and what it returns:

text.find needle haystack -> Numb

This reads: apply text.find to needle, then apply the result to haystack, and you get a number. The description says what types the arguments must have.

Curried functions

Functions with two parameters are curried: they take the first argument and return a function that takes the second. You can call them in one go, or keep the intermediate function:

text.find "l" "hello"          # => 2
find_l = text.find "l"
find_l "world"                 # => 3

The first argument is the one you are most likely to fix in advance, such as the separator of text.split or the exponent of math.pow. Note that text.find ("l", "hello") passes a single tuple, not two arguments, and does not work.

Tuples

Unless an entry says otherwise, functions are applied to each item of a tuple argument and return a tuple of results. A Nothing argument gives Nothing.

text.upper ("a", "b")          # => ("A", "B")
text.find ("l", "o") "hello"   # => (2, 4)
text.upper ()                  # => ()

Functions that reduce a tuple to one value, such as bool.all and math.max, say so in their entry.

Errors

A function given an argument of the wrong type returns Undefined. The undefined value names the function in its op member.

text.size 42                   # => Undefined
(undef.inspect (text.size 42)).op        # => "text.size"