Fixes some bugs

Signed-off-by: Irina Chichikova <diva.artim@gmail.com>
Fixes Built-In Functions, issue #22

Fixes #22

Signed-off-by: Irina Chichikova <diva.artim@gmail.com>
Fixes Declared Functions, issue #26

Signed-off-by: Irina Chichikova <diva.artim@gmail.com>
Fixes Built-In Functions, issue #25

Fixes #25

Signed-off-by: Irina Chichikova <diva.artim@gmail.com>
fixes Built-In Functions, issue #24

Fixes #24

Signed-off-by: Irina Chichikova <diva.artim@gmail.com>
Fixes Built-In Functions, issue #23

Fixes #23

Signed-off-by: Irina Chichikova <diva.artim@gmail.com>