Procedural Programming Just Like C (with pointers)

[coconParticipant]

Some notes on programming with pointers in Monkey. In some cases where you want to send an object to a function and change it. However there are some reasons of why this not happens out of the box. Structs are passed by value which means that the object is copied each time is sent to a function. Classes are a little bit different because they are sent as references which means that changes can be made, however the object itself can’t be allocated (which makes them not pure references but copy to references actually).

Jumping straight to example.

Monkey

#Import "<std>" Using std.. ' a classic struct here Struct TheStruct Field A:String Field B:Int Method To:String() Return A + " " + B End End ' a class also Class TheClass Field A:String Field B:Int Method To:String() Return A + " " + B End End ' this function will allocate a new struct ' notice the strange s[0] notation? is important! 🙂 Function TheStruct_Create(s:TheStruct Ptr) s[0] = New TheStruct End ' this one does some assignment ' notice the pointer operator [->] which means ' that I won't have to dereference the variable first to use dot operator [.] Function TheStruct_Init(s:TheStruct Ptr, n:String, i:Int) s->A = n s->B = i End ' the same concept as TheStruct_Init Function TheStruct_Update(s:TheStruct Ptr) s->B += 1 End ' it is clearly seen that structs need to ' be passed as pointers if to be changed or allocated ' same concept as the struct here Function TheClass_Create(c:TheClass Ptr) c[0] = New TheClass End ' and the same Function TheClass_Init(c:TheClass Ptr, n:String, i:Int) c->A = n c->B = i End ' however here is some special case ' because classes are passed by reference ' you can actually skip pointer usage for good ' (unless for sure you want to do the object initialization) Function TheClass_Init2(c:TheClass, n:String, i:Int) c.A = n c.B = i End Function Main() Local a:TheStruct TheStruct_Create(Varptr a) TheStruct_Init(Varptr a, "Default Struct", 1000) TheStruct_Update(Varptr a) Print(a) Local b:TheClass TheClass_Create(Varptr b) TheClass_Init(Varptr b, "Default Class", 5000) Print(b) TheClass_Init2(b, "Nice", 1) Print(b) End

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#Import "<std>" Using std..   ' a classic struct here Struct TheStruct Field A:String Field B:Int Method To:String() Return A + " " + B End End   ' a class also Class TheClass Field A:String Field B:Int Method To:String() Return A + " " + B End End   ' this function will allocate a new struct ' notice the strange s[0] notation? is important! Function TheStruct_Create(s:TheStruct Ptr) s[0] = New TheStruct End   ' this one does some assignment ' notice the pointer operator [->] which means ' that I won't have to dereference the variable first to use dot operator [.] Function TheStruct_Init(s:TheStruct Ptr, n:String, i:Int) s->A = n s->B = i End   ' the same concept as TheStruct_Init Function TheStruct_Update(s:TheStruct Ptr) s->B += 1 End   ' it is clearly seen that structs need to ' be passed as pointers if to be changed or allocated     ' same concept as the struct here Function TheClass_Create(c:TheClass Ptr) c[0] = New TheClass End   ' and the same Function TheClass_Init(c:TheClass Ptr, n:String, i:Int) c->A = n c->B = i End   ' however here is some special case ' because classes are passed by reference ' you can actually skip pointer usage for good ' (unless for sure you want to do the object initialization) Function TheClass_Init2(c:TheClass, n:String, i:Int) c.A = n c.B = i End   Function Main() Local a:TheStruct TheStruct_Create(Varptr a) TheStruct_Init(Varptr a, "Default Struct", 1000) TheStruct_Update(Varptr a) Print(a) Local b:TheClass TheClass_Create(Varptr b) TheClass_Init(Varptr b, "Default Class", 5000) Print(b) TheClass_Init2(b, "Nice", 1) Print(b) End

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