Subtract from Variable "-="

<num_var> -= <number>

Operators: Subtract from Variable "-="
Operators: Subtract "-"Subtract Glossary: Valuevalue from Glossary: Variable, var_refvariable.

Both Glossary: Operator
Glossary: Operandoperands must be numeric. Flow control: if … thenIf any of both Vipsi command syntax: Arguments
Glossary: Argumentsarguments is a Data Types: Text
Item selector "[]": Text
Glossary: text, text_valtext, Flow control: if … then
Flow control: try … thenthen it is evaluated as Glossary: number, num_valnumber. Flow control: if … thenIf List functions: thisthis conversion fails Flow control: if … then
Flow control: try … thenthen an error is generated.

Flow control: if … thenIf any of both is a Data Types: Lists and arrays
Item selector "[]": Lists
Glossary: list, list_vallist, Flow control: if … then
Flow control: try … thenthen Flow control: if … then
Flow control: try … thenthe operation is performed on all items. Recursively.

e.g.:

vipsi> Instructions: var
How does VScript::Value() work?: Var*&var a=33, b
vipsi> b = a -= 20
vipsi> Instructions: putput a, ",", b  13,13
vipsi> a -= {1,"2",3}  = { 12, 11, 10 }
vipsi>  

Operators: Bitwise Not "~"
Operators: Boolean Negation "!"Note: Operators: Assignment "="
Built-in operators: Assignments:Assignment Vipsi command syntax: Operators
Operators
Glossary: Operatoroperators Flow control: do … loopdo Operators: Bitwise Not "~"
Operators: Boolean Negation "!"not Flow control: returnreturn a result Glossary: Valuevalue. There are syntactical ambiguities with Flow control: if … then
Flow control: try … thenthe "=" Numeric functions: signsign e.g. in Literals: List literals
Lists and arrays: List literalslist literals. List functions: thisThis also allows named items in other places, e.g. passing named Vipsi command syntax: Arguments
Glossary: Argumentsarguments to Vipsi command syntax: Procedures
Data Types: Procedures
Glossary: Procedureprocedures for a obj-C-like syntax. (planned for Flow control: if … then
Flow control: try … thenthe future)