🔍

shadow

Creates variables that are visible down the stack.

Syntax: shadow `x; x::y; .x:y

Allowed only inside lambda's body, otherwise it doesn't make sense.

o)f:{s::20;};
o)f2:{shadow `s; s::10;f[];s};
o)f2[]
20
o)

o)a:42;
o){shadow `a; a::2; show a;{show a; {show a}[ ] }[ ] }[ ]
2
2
2

Always use the verb shadow in pair with :: otherwise you will use a local variable.

o)a:42;
o){shadow `a; a:2; show a;{show a; {show a}[ ] }[ ] }[ ]
2
2
0N0

For shadow variable it is more convenient to use names that start with a dot.

o){.a:2; show .a;{show .a; {show .a}[ ] }[ ] }[ ]
2
2
2

A shadow variable in a lambda overshadows a variable with the same name only after its initialization (unlike a local variable).

o).a:42;
o){ show .a; }[]
42
o){show .a; .a:2; show .a }[]
42
2
o).a
42
o)