Fargo (Function argument-o) is an esolang created by User:PythonshellDebugwindow.
Fargo is a functional esolang. Each line is either a function definition, a function call, a blank line, or a comment.
Fargo uses an input number, an integer which is defined by the interpreter (typically to be a user-input number) before the program begins. It also uses an output number, which can be output at any time in the program.
A function can be called by typing its name followed by a space, then its (space-separated) arguments, which are evaluated from left to right.
Function definitions are rather unorthodox in Fargo. Each definition takes up exactly one line (excluding comments). The first token of a function definition is its name (redefining an existent function is an error); the rest of the tokens are its arguments and its code. The divide between arguments and code is fairly unusual: the first defined name is the first code token, and the previous token is the final argument. Defined names are built-in functions, user-defined functions (including the function being defined), and the arguments of the function currently being defined.
Functions must contain exactly one outer function call (e.g.,
myFn x y z otherFn x thirdFn y z is legal while
myFn x y z otherFn x y z anotherFn x and
myFn are not; even though the first example calls
thirdFn, it doesn't do so at the top level).
If a token begins with a
: colon, it either represents a raw function (as opposed to a function call), which can be used as an argument to a function, if it is not a function argument; or marks a function argument as being a raw function, rather than a value.
Literals are binary integers matching the regex /[0-1]+/.
Comments are declared by using
#, and last until the end of the line.
< xreturns x right-shifted by 1
> xreturns x left-shifted by 1
& x yreturns x bitwise-AND y
| x yreturns x bitwise-OR y
^ x yreturns x bitwise-XOR y
 xreturns an array with only x in it
+ x yreturns the array x concatenated with the array y
[?] x yreturns the yth element of the array x
@ xreturns the xth bit of the input number (LSB = 0th bit)
% x ysets the xth bit of the output number to y (LSB = 0th bit)
$outputs the output number in base-10
: x ydoes y iff x is unequal to zero
one ^ $ one % 0 @ 0 : @ 0 one $