@is_subsequence(s1:string, s2:string)
@is_subsequence(s1:string, s2:string, cmp:fct)
@is_subsequence(t1:tab, t2:tab)
@is_subsequence(t1:tab, t2:tab, cmp:fct)
@is_subsequence is an overloaded function. See also the functions @is_suffix and @is_prefix.

@is_subsequence(s1:string, s2:string)
the function returns the index of the first occurrence of string s1 in string s2. A negative value is returned if s1 does not occurs in s2.

@is_subsequence(s1:string, s2:string, cmp:fct)
same as above but the argument cmp is used to compare the characters of the strings (represented as strings of only one element).

@is_subsequence(t1:tab, t2:tab)
the predicate returns the index of the first occurrence of the elements of t1 as a sub-sequence of the elements of t2. A negative value is returned if t2 does not appear as a subsequence of tab t2. For example 
              @is_subsequence([], [1, 2, 3]) -> 0
       @is_subsequence([1, 2, 3], [1, 2, 3]) -> 0
             @is_subsequence([1], [1, 2, 3]) -> 0
             @is_subsequence([2], [1, 2, 3]) -> 1
             @is_subsequence([3], [1, 2, 3]) -> 2
       @is_subsequence([1, 2], [0, 1, 2, 3]) -> 1


@is_subsequence(t1:tab, t2:tab, cmp:fct)
same as the version above but the function cmp is used to compare the elements of the tabs.

See also Predicates @!=    @&&    @||    @<=    @<    @==    @>=    @>    @approx    @arch_darwin    @arch_linux    @arch_windows    @between    @empty    @find    [@is_applicable]    [@is_applicable_exe]    @is_bool    @is_defined    @is_exec    @is_fct    @is_float    @is_fct    [@is_fun]    @is_function    @is_int    @is_integer_indexed    @is_list    @is_map    [@is_Napplicable]    @is_nim    [@is_not_initialized]    @is_numeric    [@is_paf]    @is_obj    @is_obj_xxx    @is_prefix    @is_proc    @is_string    [@is_string_or_symbol]    @is_subsequence    @is_suffix    @is_symbol    @is_tab    @is_undef    @is_vector    @member    @occurs