Category:M2000 Interpreter: Difference between revisions

For Expressions before execution automatic check by names if the result can be for strings names, or for numeric names. A string name has $ at the end of name. Maybe a string name isn't a string, because with same name we can define groups which get or and return strings values. A statement Input Alfa$ can input characters for a string or for object typed group with that name. Interpreter implicitly use the appropriate method. If name has no $ at the end then this can be an object or a numeric value. A Input Beta may return error if Beta has no numeric value to set.

Types are strong for values with a name (variables, constants), but weak for items in containers. In a container (Array, Inventory and Stack) we can place anything including other containers. We can bypass the "strong" capability but this isn't a practice for good programming. Internal or variables are of type of Variant, so we can make a reference of A to A$ and we can save a string "1212" and read from A the number 1212.

<lang >

Module AKindOfMess {

a=10@

Print Type$(a)="Decimal"

\\ a and a$ reference same variant type

Link a to a$

Print a$

Let a$=str$(500.12, "")

Rem : a++ ' error can't aply ++ to a string type

Print type$(a)="String" ' true

' Error a=a+a

Print len(a$)

Print a=500.12 ' true

a$+=a$

Print len(a$)

Print a$, a=0

a$=Left$(a$, len(a$)/2)

Print a$

Print a=500.12

let a=100@

Print Type$(a)="Double"

Print a$="100" ' true

For This {

M=23451234512345123451234512345@

swap M, a

}

Print Valid(M)=false ' M not exist now

Print Type$(a)="Decimal" ' true

Print a$="23451234512345123451234512345" ' true

}

AKindOfMess

Print Valid(a)=false ' not exist

Print Valid(a$<>"")=false ' not exist

Print Valid(12/0)=false ' evaluate expression and return true if is ok (errors trapped always)

Print Error$=""

</lang>

So check this for proper use of types.