PocketC Language updated for B1.29

The language is very similar to standard C in syntax, but has a different feature set. Most notably, there are no pointers, no structs, and no preprocessor. A string data type has been added, and values are somewhat loosely typed. The next section is for those who are already somewhat familiar with C.

Brief guide to the PocketC language

Data Types

There are four types in PocketC: integers (int), floating point numbers (float), characters (char), strings (string), and single-dimensional arrays.

Expressions

An expression consists of any number of variables, function calls, and constants of any type, joined by operators and parentheses. Thus, the following expressions are valid:

3 + 5

6.7 + 23

"Hello " + "World"

5*3 + foobar()

When an expression contains values of different types, the two values are first cast to the same type, and then the operator applied. For example in the following expression:

 5.7 + 8

 The 8 is first cast to a float (8.0), and the two numbers are added (5.7 + 8.0). This becomes slightly more interesting when we use strings. For example:

 "The result is " + (5 + 8)

 5 is first added to 8, resulting in 13. The 13 is then converted to a string, and appended to "The result is " resulting in "The result is 13". However,

 "The result is " + 5 + 8

 would result in "The result is 58", since the the 5 is first converted to a string, then appended to "The result is "...

 Of course, explicit casting is possible:

 56 + (int)"7"

 evaluates to 63.

 The following operators are provided (in order of precedence, with associativity):

Note: No shortcut logic is performed on the operands of || and &&
Note2: The +=, -=, *=, etc. operators are not supported.

Variables

• The following variable types are supported: int, float, char, string, and single-dimensional arrays.
• Local variables must be declared before any code in a function.
• Variable initializers are not yet supported. (e.g. int x=5; is not yet legal).
• All variables, global and local, are initialized to zero or the empty string.

Statements

The following statements are fully supported: for, while, do, switch, case, break, continue, if, then, return.
Note: for requires a condition expression (i.e. for (;;) is not legal, instead, use for (;1;) or while (1))

Functions

• Functions are declared without a return type. Because of loose typing, it is possible to return any type or even multiple types.
• Local variables must come before any function code.
• Recursion is allowed.
• There must be a main function that takes no parameters.
• Functions cannot take arrays as parameters.
• A function cannot be called before it is defined.
• Forward declarations are not allowed.

Preprocessor

• Following keywords are supported: #define, #ifdef, #ifndef, #else, #endif
• You cannot include files recursively (you wouldn't want to anyway)
• Only three levels of includes are supported

Example:

// My large applet

#include "ctrlheader.h"

#include "appheader.pc"

#define BUTTON	"button"

#define PI	3.1415926

#define VERSION	100

main() {

// use predefined value in other header files

// call functions defined in other files

}

Special characters

There are two ways to add special characters to a string. The first is by appending them by number, such as:

str = "Here is a neat little square: " + (char)149;

The other method is through using escape sequences. The following escape sequences are supported: