interface for numerical integration, roots etc



If it were a popularity contest, it looks like ':'
would win. = and => are also popular. Mathematica's -> is
not mentioned.

From Rosetta Code
These are either true named parameters or simulated with
data structures. Some of the examples without true
named parameters are conventions, a few are example implementations.

Ada           =>
AppleScript   :
AutoHotkey    =
C++           foo(foo_params(42).x(7).z(23.54));
Clojure       :key   (like lisp)
Common lisp   :key  (no infix)
E             =>
Fortran 95    =
Haskell       ' '   
J             =
JavaScript    :
Modula-3      :=
Objective-C   :
OCaml         :    ~key:val  (needs ~)
Oz            :
Perl          =>
Python        =  (there areseveral kinds, * and ** are identifier prefixes)
Ruby          =>
Scala         =
Scheme        'key   (no infix)
Smalltalk     :
Suneido       :
Tcl           -key val
VB            :=