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[compsystems]

Index acts as a system variable and as a functional command,

For functional command:
Index() returns the first position of an object in a list, a string or a set, if it does not find the object returns an error message.

index(List/String/Set,Object)

LIST:
index:=0:; index([9,8,-1,8,9,8,7],8) [↵] returns 1 // ok
index:=1:; index([9,8,-1,8,9,8,7],8) [↵] returns 2 // ok

SET:
index:=0:; F_ := set[ H_,E_,L_,L_,O_];
F_ => set[ H_,E_,L_,O_]; // the multiplicity of L_ is eliminated // ok
index(F_,O_) [↵] returns 3 // ok
index(F_,L_) [↵] returns 2 // ok

STRING
index:=0:; index("abracadabrant","c") [↵] returns -1 (Bug)// GIAC => 4