mirror of
https://codeberg.org/andyscott/ziglings.git
synced 2024-11-08 11:20:46 -05:00
74 lines
3 KiB
Zig
74 lines
3 KiB
Zig
//
|
|
// "Compile time" is a program's environment while it is being
|
|
// compiled. In contrast, "run time" is the environment while the
|
|
// compiled program is executing (traditionally as machine code
|
|
// on a hardware CPU).
|
|
//
|
|
// Errors make an easy example:
|
|
//
|
|
// 1. Compile-time error: caught by the compiler, usually
|
|
// resulting in a message to the programmer.
|
|
//
|
|
// 2. Runtime error: either caught by the running program itself
|
|
// or by the host hardware or operating system. Could be
|
|
// gracefully caught and handled or could cause the computer
|
|
// to crash (or halt and catch fire)!
|
|
//
|
|
// All compiled languages must perform a certain amount of logic
|
|
// at compile time in order to analyze the code, maintain a table
|
|
// of symbols (such as variable and function names), etc.
|
|
//
|
|
// Optimizing compilers can also figure out how much of a program
|
|
// can be pre-computed or "inlined" at compile time to make the
|
|
// resulting program more efficient. Smart compilers can even
|
|
// "unroll" loops, turning their logic into a fast linear
|
|
// sequence of statements (at the usually very slight expense of
|
|
// the increased size of the repeated code).
|
|
//
|
|
// Zig takes these concepts further by making these optimizations
|
|
// an integral part of the language itself!
|
|
//
|
|
const print = @import("std").debug.print;
|
|
|
|
pub fn main() void {
|
|
// ALL numeric literals in Zig are of type comptime_int or
|
|
// comptime_float. They are of arbitary size (as big or
|
|
// little as you need).
|
|
//
|
|
// Notice how we don't have to specify a size like "u8",
|
|
// "i32", or "f64" when we assign identifiers immutably with
|
|
// "const".
|
|
//
|
|
// When we use these identifiers in our program, the VALUES
|
|
// are inserted at compile time into the executable code. The
|
|
// identifiers "my_int" and "my_float" don't really exist in
|
|
// our compiled application and do not refer to any
|
|
// particular areas of memory!
|
|
const const_int = 12345;
|
|
const const_float = 987.654;
|
|
|
|
print("const_int={}, const_float={d:.3}, ", .{const_int, const_float});
|
|
|
|
// But something changes when we assign the exact same values
|
|
// to identifiers mutably with "var".
|
|
//
|
|
// The literals are STILL comptime_int and comptime_float,
|
|
// but we wish to assign them to identifiers which are
|
|
// mutable at runtime.
|
|
//
|
|
// To be mutable at runtime, these identifiers must refer to
|
|
// areas of memory. In order to refer to areas of memory, Zig
|
|
// must know exactly how much memory to reserve for these
|
|
// values. Therefore, it follows that we just specify numeric
|
|
// types with specific sizes. The comptime numbers will be
|
|
// coerced (if they'll fit!) into your chosen runtime types.
|
|
var var_int = 12345;
|
|
var var_float = 987.654;
|
|
|
|
// We can change what is stored at the areas set aside for
|
|
// "var_int" and "var_float" in the running compiled program.
|
|
var_int = 54321;
|
|
var_float = 456.789;
|
|
|
|
print("var_int={}, var_float={d:.3}\n", .{var_int, var_float});
|
|
}
|