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Diffstat (limited to 'doc/lispref/functions.texi')
| -rw-r--r-- | doc/lispref/functions.texi | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/doc/lispref/functions.texi b/doc/lispref/functions.texi index 222f863c988..97f7fb9f79e 100644 --- a/doc/lispref/functions.texi +++ b/doc/lispref/functions.texi @@ -38,11 +38,16 @@ define them. @cindex return value @cindex value of function @cindex argument +@cindex pure function In a general sense, a function is a rule for carrying out a computation given input values called @dfn{arguments}. The result of the computation is called the @dfn{value} or @dfn{return value} of the function. The computation can also have side effects, such as lasting -changes in the values of variables or the contents of data structures. +changes in the values of variables or the contents of data structures +(@pxref{Definition of side effect}). A @dfn{pure function} is a +function which, in addition to having no side effects, always returns +the same value for the same combination of arguments, regardless of +external factors such as machine type or system state. In most computer languages, every function has a name. But in Lisp, a function in the strictest sense has no name: it is an object which |