QBasic pass type as function argument -

went old qbasic nostalgic reasons , have never used types , functions in qbasic before young time.

type vector2     x single     y single end type  function vector2mag (a vector2)     vector2mag = sqr((a.x * a.x) + (a.y * a.y)) end function  function vector2add (a vector2, b vector2)     dim r vector2     r.x = a.x + b.x     r.y = a.y + b.y     vector2add = r end function 

but get

illegal sub/function parameter on current line 

using qb64 in both first function lines. google didn't looks doing right. checked passing multiple variables, specifying type parameter, how use types nothing helped.

thanks guys.

it has been while, believe problem can't return udt (user defined type, a.k.a. "any type not built in"). need pass third argument vector2add , make sub. example:

sub vector2add (r vector2, vector2, b vector2)     r.x = a.x + b.x     r.y = a.y + b.y end sub 

the sub exact translation equivalent c code, aside syntax differences. reasoning add type suffix name of function in qb or use default type, may have been overridden defxxx m-n (or _define in qb64; , no can't use _define udts). example, returning string:

'default type identifiers beginning 's' string. ' type suffixes, "as xxxx" clauses , future "defxxx" items override behavior. defstr s-s  function swapfirstlast$ (s)     swapfirstlast$ = right$(s, 1) + mid$(s, 2, len(s) - 2) + left$(s, 1) end function 

qb64 kinda limited in regard since aims compatible syntax used quickbasic 4.5 possible. freebasic, language based on qb, has no such restriction:

'notice "as vector2" @ end of next line , return statement ' fb introduced functions (originally used return ' "old-style" subroutine invoked via gosub statement). function vector2add (a vector2, b vector2) vector2     dim r vector2     r.x = a.x + b.x     r.y = a.y + b.y     return r end function 

the important point remember qb64 still qb, except compile code run on modern operating systems (rather dos). freebasic, on other hand, chose sacrifice compatibility in favor of creating more "modern" language retains qb's syntax.