everyday programs and exceptions

Question 1

base library

Answer 1

provides the core runtime

Question 2

hackage

Answer 2

third party libraries

Question 3

what are some of the top level module hierarchies

Answer 3

control
data
foreign
ghc
system
text

Question 4

control module

Answer 4

control-flow and functions
e.g.exceptions, concurrency

Question 5

data module

Answer 5

representation
e.g. graphs and trees

Question 6

foreign module

Answer 6

interactivity with other languages via the ffi (foreign function interface)

Question 7

which language do we usually use to call haskell functins

Answer 7

c

Question 8

ghc module

Answer 8

compiler specific

Question 9

system module

Answer 9

interactivity with the os, command line, variables, processes etc
e.g. io functions

Question 10

text module

Answer 10

representing texts without using strings

Question 11

what is a benefit of the text module

Answer 11

enables language conversion

Question 12

when should we use exceptions

Answer 12

for things that go wrong rarely not as regular error reporting
e.g. cant write as the disk is too full

Question 13

what is the module for exceptions

Answer 13

control.exceptions

Question 14

what are the three main types of exceptions and what are they used for

Answer 14

IO exception: for io actions
ErrorCall: generated by calling the error function
SomeException: represents every type of error

Question 15

how is control.exceptions represented

Answer 15

via data

Question 16

how can we make our own error handling without using exceptions

Answer 16

have a run function that calls the function doing the data
that function returns 2 values in a tuple with one of them being a number indicating whether there was an error
the run function takes this and calls the appropriate exception handling function if required

Question 17

why do we make our own error handling without using exceptions

Answer 17

haskell doesnt have a control flow in the same way that java does

Question 18

what does the chaining function look like and what does it do

Answer 18

> > =
used for multiple io functions and updates the state of the world as it goes

Question 19

data.char

Answer 19

for individual characters
e.g. upper to lower case and back
unicode and back

Question 20

data.list

Answer 20

more complex that the list functions in the prelude
can also be used on strings as theyre a list of characters

Question 21

lines (data.list)

Answer 21

creates an array from a given string with \n being the separator

Question 22

unlines (data.list)

Answer 22

creates a string from an array with \n between

Question 23

words (data.list)

Answer 23

creates an array from a given string with white space as separators

Question 24

unwords (data.list)

Answer 24

creates a string from an array with white spaces between

Question 25

concat (data.list)

Answer 25

combines lists

Question 26

concatMap (data.list)

Answer 26

combines lists then maps them into one list

Question 27

which 3 functions can we use to split lists

Answer 27

span break splitAt

Question 28

fromMaybe

Answer 28

just = returns the value nothing = returns the default

Question 29

mapMabye

Answer 29

maps only the just values

Question 30

what does the catch function definition look like

Answer 30

catch :: Exception e => IO a -> (e -> IO a) -> IO a

Question 31

how does the catch function work

Answer 31

it has a constraint so e has to be an exception it takes in an io and an exception handler if no error then just returns the io if error then runs the handler and returns the value from that

Question 32

how do we pass in a list of handlers into the catch functin

Answer 32

must create a handler type and make the exceptions equal to it as the catch function requires all the exceptions to be the same type