Syntax

expression1 + expression2

Description

Adds or concatenates two expressions.

Comments

Addition operates differently depending on the type of the two expressions:

If one 
expression is

and the other 
expression is

then

Numeric

Numeric

Perform a numeric add (see below).

String

String

Concatenate, returning a string.

Numeric

String

A runtime error is generated.

Variant

String

Concatenate, returning a String variant.

Variant

Numeric

Perform a variant add (see below).

Empty variant

Empty variant

Return an Integer variant, value 0.

Empty variant

Boolean variant

Return an Integer variant (value 0 or -1)

Empty variant

Any data type

Return the non-Empty expression unchanged.

Null variant

Any data type

Return Null.

Variant

Variant

If either is numeric, add; otherwise, concatenate.

When using + to concatenate two variants, the result depends on the types of each variant at runtime. You can remove any ambiguity by using the & operator.

Numeric Add

A numeric add is performed when both expressions are numeric (i.e., not variant or string). The result is the same type as the most precise expression, with the following exceptions:.

If one
expression is

and the other
expression is

then

Single

Long

Double

Boolean

Boolean

Integer

A runtime error is generated if the result overflows its legal range

Variant Add

If both expressions are variants, or one expression is numeric and the other expression is Variant, then a variant add is performed. The rules for variant add are the same as those for normal numeric add, with the following exceptions:

If the type of the result is an Integer variant that overflows, then the result is a Long variant.

If the type of the result is a Long, Single, or Date variant that overflows, then the result is a Double variant.

Example

This example assigns string and numeric variable values and then uses the + operator to concatenate the strings and form the sums of numeric variables.

Sub Main()
  i$ = "concatenate " + "strings!"
  j% = 95 + 5     'Addition of numeric literals
  k# = j% + j%    'Addition of numeric variable
  MsgBox "You can " + i$
  MsgBox "You can add literals or variables:" + Str(j%) + ", " + Str(k#)
End Sub

See Also

& (Operator); Operator Precedence (topic)

Symbols