Function --

-- symbol

Modifies the contents of a variable containing a numeric object by subtracting one from its previous value.

Parameters:

symbol - A symbol object identifying a variable in the current context. The variable must contain a numeric object.

Returns:

The new value of the variable.

Modifies the contents of the variable identified by symbol by decrementing by one the value it had previously stored. The variable binded to symbol is expected to contain a numeric object.

The -- is a short way to write

    set! symbol [- $symbol 1]