Call a function: Difference between revisions

=={{header|Factor}}==

* Calling a word with no arguments:

<lang Factor>

foo

</lang>

* Calling a word with a fixed number of arguments. This will pull as many objects as it needs from the stack. If there are not enough, it will result in a stack underflow.

<lang Factor>

foo

</lang>

* No special support for optional arguments.

* Variable arguments are achieved by defining a word that takes an integer, and operates on that many items at the top of the stack:

<lang Factor>

"a" "b" "c" 3 narray

</lang>

* The named arguments idiom is to define a tuple, set its slots, and pass it to a word:

<lang Factor>

<email>

"jack@aol.com" >>from

{ "jill@aol.com" } >>to

"Hello there" >>subject

body >>body

send-email

</lang>

* Factor lacks statements; everything is an expression.

* First-class context: this pushes a word to the stack. Use execute to evaluate.

<lang Factor>

\ foo

</lang>

Additionally, you can put words directly inside sequences and quotations:

<lang Factor>

{ foo } [ foo ]

</lang>

* Obtaining the return value, which will be placed on the stack:

<lang Factor>

foo

</lang>

* Returns true if the word is defined in the Factor VM as opposed to in a vocabulary:

<lang Factor>

\ foo primitive?

</lang>

* Factor makes no distinction between subroutines and functions. Presumably, a subroutine is just a word which puts nothing on the stack.

* By value or by reference is irrelevant; Factor is not applicative.

* Partial application is possible by use of curry. Here, the object 2 is curried into the left side of the quotation (anonymous function) [ - ]:

<lang Factor>

{ 1 2 3 } 2 [ - ] curry map .

! { -1 0 1 }

</lang>