LPC_GPIO1->DIR - What does this mean?

Now that I have written a couple of functions to make it easier to resuse the blinky function for LEDs. I hope to make it also useful for keys and beeps.  But there is one thing that puzzles me.  What is the meaning of LPC_GPIOx.  Is it a variable hidden somewhere?  And what is the meaning of the symbol "->"?  I know the meaning of >> and <<.  But I have the feeling that -> is similar to the dot thing in object programming.

Anyway, I dug into the header files and found that LPC_GPIOx is defined in system_lpc11xx.h.  It says the following.

/*  Peripheral memory map  */
/* Base addresses */
...
#define LPC_AHB_BASE          (0x50000000UL)

...

/* AHB peripherals */
...
#define LPC_GPIO_BASE         (LPC_AHB_BASE  + 0x00000)

/* Peripheral declaration */
...
#define LPC_GPIO1             ((LPC_GPIO_TypeDef   *) LPC_GPIO1_BASE )

So I now guess LPC_GPIOx is a variable representation a might be a control register mapped to a memory location.  But what is the following weird thing?

 ((LPC_GPIO_TypeDef   *) LPC_GPIO1_BASE )

It appears that I need to dig deeper.


system_lpc11xx.h

...

/******************************************************************************/
/*                         Peripheral memory map                              */
/******************************************************************************/
/* Base addresses                                                             */

...

#define LPC_AHB_BASE          (0x50000000UL)

...

/* AHB peripherals                                                            */
#define LPC_GPIO_BASE         (LPC_AHB_BASE  + 0x00000)
#define LPC_GPIO0_BASE        (LPC_AHB_BASE  + 0x00000)
#define LPC_GPIO1_BASE        (LPC_AHB_BASE  + 0x10000)
#define LPC_GPIO2_BASE        (LPC_AHB_BASE  + 0x20000)
#define LPC_GPIO3_BASE        (LPC_AHB_BASE  + 0x30000)

/******************************************************************************/
/*                         Peripheral declaration                             */
/******************************************************************************/

#define LPC_GPIO1             ((LPC_GPIO_TypeDef   *) LPC_GPIO1_BASE )
#define LPC_GPIO2             ((LPC_GPIO_TypeDef   *) LPC_GPIO2_BASE )
#define LPC_GPIO3             ((LPC_GPIO_TypeDef   *) LPC_GPIO3_BASE )