This nearly the same as atom_concat/3 but it doesn't generate substrings from the 3rd argument if asked to do so.

Your choices

Your choice of predicate is as follows:

Two concatenable terms as input (can split)

• atom_concat/3 (ISO)
• string_concat/3

Two more general concatenable terms as input (cannot split because arguments 1 and 2 are too general)

• atomic_concat/3

A list of concatenable terms as input (never split)

• atomic_list_concat/2 - generates atom at argument 2. Refuses string at argument 2 in accept mode (that's likely a bug).
• atomics_to_string/2 - generates string at argument 2. Refuses atom at argument 2 in accept mode (that's likely a bug).

A list of concatenable terms as input, and intersperse another string (can split at interspersed string)

• atomic_list_concat/3 - concatenate with separator ("intersperse", "join"). Refuses string at argument 3 in accept mode (that's likely a bug).
• atomics_to_string/3 - concatenate with separator ("intersperse", "join"). Refuses atom at argument 3 in accept mode (that's likely a bug).

Test code

:- begin_tests(atomic_concat).

test("atomic_concat/3 generates atom at the 3rd argument") :-
   atomic_concat(a,b,X),
   assertion(X==ab).
   
test("atomic_concat/3 in 'accept mode' allows string at 3rd argument") :-
   atomic_concat(a,b,"ab").

test("atomic_concat/3 accepts string at argument 1 and 2") :-
   atomic_concat("a",b,X),
   assertion(X==ab),
   atomic_concat(a,"b",Y),
   assertion(Y==ab),
   atomic_concat("a","b",Z),
   assertion(Z==ab).
   
test("atomic_concat/3 actually accepts atomic at argument 1 and 2 and even 3") :-
   atomic_concat(1,2,X),
   assertion(X=='12'),
   atomic_concat(1,2,12).

test("atomic_concat/3 refuses to generate",error(instantiation_error)) :-
   atomic_concat(_X,_Y,ab).
   
:- end_tests(atomic_concat).