functional programming - Troubleshooting a haskell function -



functional programming - Troubleshooting a haskell function -

i learning haskell , have problems understanding errors trying tell me. code produces next error

data term = mul { factor :: term, factor2 :: term } | div { dividend :: term, divisor :: term } | add together { summand :: term, summand2 :: term } | sub { minuend :: term, subtrahend :: term } | mon { exponent :: int } value :: (double, term) -> double value x (mul b) = (value x a) * (value x b) value x (div b) = (value x a) / (value x b) value x (add b) = (value x a) + (value x b) value x (sub b) = (value x a) - (value x b) value x (mon a) = x^a

error:

couldn't match expected type `term -> (double, term)' actual type `double' function `value' applied 2 arguments, type `(double, term) -> double' has 1 in first argument of `(+)', namely `(value x a)' in expression: (value x a) + (value x b)

what doing wrong?

the problem type signature , definitions don't agree on how taking arguments.

you need either write type signature in curried style (recommended):

value :: double -> term -> double

or write function in uncurried style (non-idiomatic):

value (x, mul b) = ...

i recommend trying both, former way done in wild.

haskell functional-programming ghc

Comments

Post a Comment

Popular posts from this blog

java - Bypassing "final local variable defined in an enclosing type" -

java - Bypassing "final local variable defined in an enclosing type" - i'm writing programme , i'm getting "the final local variable asd cannot assigned, since it's defined in enclosing type". i provide illustration not code produces error aswell. have arraylist utilize later (if define within button can't utilize later on), outside of button, pressing button should give values arraylist. in illustration "create new arraylist" cause same problem. button btn = new button("asd"); final arraylist asd = new arraylist(); btn.setonaction(new eventhandler<actionevent>() { public void handle(final actionevent event) { asd = new arraylist(); //here's error.. } }); clear arraylist , add together values. java javafx
Read more

Delphi change the assembly code of a running process -

Delphi change the assembly code of a running process - i'm trying alter address 00741fa5 has push test.009e721c . alter push test.009e71c8 . procedure callback; asm force $9e71c8 end; procedure tform2.btn1click(sender: tobject); var ppid :dword; pprocess : cardinal; begin getwindowthreadprocessid(findwindow(nil,pchar('test')), @ppid); pprocess := openprocess(process_all_access, false, ppid); injectasm(pprocess, $741fa5, 10, integer(@callback), 0); end; here injectasm function (with error checking) function injectasm(process: longword; injectaddress, injectsize, codeaddress, codesize : integer): pointer; var csize, rsize : integer; replaced : array of byte; jmp : array [0..4] of byte; jmpaddress : integer; nopv : byte; : integer; nbr: ulong_ptr; begin //injectsize must equal or greater 5, because need space our //(far) jmp wwxxyyzz instruction //if there's no space, inject in place of few instructions if injectsize ...
Read more

json - Hibernate and Jackson (java.lang.IllegalStateException: Cannot call sendError() after the response has been committed) -

json - Hibernate and Jackson (java.lang.IllegalStateException: Cannot call sendError() after the response has been committed) - hello have problem hibernate , jackson. have 2 pojos @entity @table(name = "users") public class user implements serializable { static final long serialversionuid = 4235637833262722256l; @id @generatedvalue private int id; @column(name = "creation_date") private date creationdate; @column(name = "first_name") private string firstname; @column(name = "last_name") private string lastname; @version @column(name = "version") private int version; @column(name = "e_mail") private string email; @column(name = "enabled") private boolean enabled; @column(name = "login") private string login; @column(name = "password") private string password; @jsonmanagedreference("role") @onetomany(mappedby = "user", cascade = cascadetype.all,fetch = fetchtyp...
Read more