A FUN-tree is represented by a Pico table whose first entry is the recognition tag (number 5). The other four entries correspond to the name of the represented function, its formal parameter list, its body expression and its lexical dictionaries. The FUN_NAM_idx, FUN_PAR_idx, FUN_EXP_idx and FUN_DCT_idx are the indexes to access the tree. E.g., if ff is a function tree, then we can select the body of that function with the expression ff[FUN_EXP_idx].