With some maliciosness it is possible to delete Glossary: Variable, var_refvariables which are currently in use. List functions: thisthis will crash vipsi. List functions: thisThis problem is probably solved in Flow control: if … then
Flow control: try … thenthe Flow control: nextnext version of vipsi after version 1.0.

vipsi> Instructions: var
How does VScript::Value() work?: Var*&var a;
vipsi> Instructions: procproc bummer() { Instructions: deldel a; Flow control: returnreturn "haha!" }
vipsi> a = bummer();
Sorry, a fatal error occured:
../Example Scripts: Librarieslibraries/Instructions: var
How does VScript::Value() work?: Var*&var/Instructions: var
How does VScript::Value() work?: Var*&var.cp in line 248: internal error
Abgebrochen
bash$

Operators and Functions with Side Effects

In an ideal world an Vipsi command syntax: Expressions
Glossary: Expressionexpression is made up out of terms which modify nothing but their result Glossary: Valuevalue, which they are expected to modify.

But there are some Vipsi command syntax: Operators
Operators
Glossary: Operatoroperators which modify their Glossary: Operator
Glossary: Operandoperands Operators: Boolean And with Variable "&&="
Operators: Bitwise And with Variable "&="
Operators: Bitwise And "&"
Operators: Boolean And "&&"and you will probably frequently Instructions: writewrite Vipsi command syntax: Procedures
Data Types: Procedures
Glossary: Procedureprocedures which Operators: Bitwise Not "~"
Operators: Boolean Negation "!"not only Flow control: returnreturn a result Glossary: Valuevalue but also modifies some List functions: globals
Shell Immediate Commands: globalsglobal data directly.

Vipsi, Operators: Boolean And with Variable "&&="
Operators: Bitwise And with Variable "&="
Operators: Bitwise And "&"
Operators: Boolean And "&&"and other computer languages, Flow control: try … thentry to avoid unneccessary copying of data. Therefore Glossary: Operator
Glossary: Operandoperands Operators: Boolean And with Variable "&&="
Operators: Bitwise And with Variable "&="
Operators: Bitwise And "&"
Operators: Boolean And "&&"and Vipsi command syntax: Arguments
Glossary: Argumentsarguments in Vipsi command syntax: Expressions
Glossary: Expressionexpressions which simply refer to a Glossary: Variable, var_refvariable are Operators: Bitwise Not "~"
Operators: Boolean Negation "!"not copied for further evaluation, but only a reference to Flow control: if … then
Flow control: try … thenthe Glossary: Variable, var_refvariable is remembered.

List functions: thisThis comes to a problem Flow control: if … then
Flow control: if … thenif the pending Glossary: Variable, var_refvariable is modified by Flow control: if … then
Flow control: try … thenthe side effect of a Vipsi command syntax: Procedures
Data Types: Procedures
Glossary: Procedureprocedure Operators: Boolean Or with Variable "||="
Operators: Bitwise Or with Variable "|="
Operators: Bitwise Or "|"
Operators: Boolean Or "||"or Vipsi command syntax: Operators
Operators
Glossary: Operatoroperator later in Flow control: if … then
Flow control: try … thenthe Vipsi command syntax: Expressions
Glossary: Expressionexpression.

List functions: thisThis is Operators: Bitwise Not "~"
Operators: Boolean Negation "!"not detected for Flow control: if … then
Flow control: try … thenthe sake of Appendix: Speedspeed. Operators: Boolean And with Variable "&&="
Operators: Bitwise And with Variable "&="
Operators: Bitwise And "&"
Operators: Boolean And "&&"and it may even be made part of Flow control: if … then
Flow control: try … thenthe syntax definition of vipsi! After all most usages List functions: thisthis way are either exotic Operators: Boolean Or with Variable "||="
Operators: Bitwise Or with Variable "|="
Operators: Bitwise Or "|"
Operators: Boolean Or "||"or knowingly abusive.

operator ++ and --

vipsi> Instructions: var
How does VScript::Value() work?: Var*&var a = 1
vipsi> a + ++a    = 4         (Operators: Bitwise Not "~"
Operators: Boolean Negation "!"not 3)

vipsi> Instructions: var
How does VScript::Value() work?: Var*&var a = 1
vipsi> a + a++    = 3         (Operators: Bitwise Not "~"
Operators: Boolean Negation "!"not 2)

Assignment operators = += -= *= /= %= #= ##= etc.

Operators: Assignment "="
Built-in operators: Assignments:Assignment Vipsi command syntax: Operators
Operators
Glossary: Operatoroperators deliberately modify their left-side Vipsi command syntax: Arguments
Glossary: Argumentsargument, Flow control: if … then
Flow control: try … thenthe bad side of our problem, Operators: Boolean And with Variable "&&="
Operators: Bitwise And with Variable "&="
Operators: Bitwise And "&"
Operators: Boolean And "&&"and in Operators: Add "+"addition to that, all modify-and-assign Vipsi command syntax: Operators
Operators
Glossary: Operatoroperators also Instructions: readread their Glossary: Valuevalue from Flow control: if … then
Flow control: try … thenthe referenced Glossary: Variable, var_refvariable, making Flow control: if … then
Flow control: try … thenthem vulnerable for our problem.

vipsi> Instructions: var
How does VScript::Value() work?: Var*&var a = 20
vipsi> a += (a=4)    = 8       (Operators: Bitwise Not "~"
Operators: Boolean Negation "!"not 24)

vipsi> Instructions: var
How does VScript::Value() work?: Var*&var a={}
vipsi> a[4]=a[3]=a    = { 0, 0, {0,0,0,0}, {0,0,0,0} }     Operators: Bitwise Not "~"
Operators: Boolean Negation "!"not:  {0,0,{},{}}

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vipsi - the friendly vip script interpreter

Appendix

Known bugs

Deleting Variables in use

Operators and Functions with Side Effects

operator ++ and --

Assignment operators = += -= *= /= %= #= ##= etc.