HP Prime CAS programming

[parisse]

CAS programs are expressions of root node 'program' (with a child of type DOM_LIST, a list of 3 arguments). If f is a variable containing a program (for example defined like this f(x):=sin(x)), type(f) will return DOM_FUNC and f[1] or f[0] (depends whether Python compatibility is enabled) is 'program'.
In contrast, if g:=sin(x), g is an expression of rootnode 'sin' (with x as child) and g[1] or g[0] is 'sin'.