Name Errors/Static/UnguardedInsert

Synopsis An insert occurs outside a visit expression.

Description An insert statement may only occur in the action part of a Rascal:PatternWithAction, more precisely in a case in a Rascal:Visit expression.

Remedies:

• Use an auxiliary variable and list or set operations to insert the value where you want.
• Place the insert statement inside a visit.

Examples Here is an example of the use of insert to swap the arguments of red nodes: Our favorite data type, colored trees:

rascal>data CTree = leaf(int n) | red(CTree left, CTree right) | green(CTree left, CTree right);
ok

An example tree:

rascal>CTree T = red(green(leaf(1), red(leaf(2), leaf(3))), red(leaf(4), leaf(5)));
CTree: red(
  green(
    leaf(1),
    red(
      leaf(2),
      leaf(3))),
  red(
    leaf(4),
    leaf(5)))

A visit to swap the arguments of red nodes:

rascal>visit(T){ case red(CTree l, CTree r): insert red(r,l); }
CTree: red(
  red(
    leaf(5),
    leaf(4)),
  green(
    leaf(1),
    red(
      leaf(3),
      leaf(2))))

An error occurs when insert is used outside a visit:

rascal>insert red(leaf(1), leaf(2));
|stdin:///|(0,29,<1,0>,<1,29>): Insert statement outside a visit statement

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