mirror of
https://codeberg.org/andyscott/ziglings.git
synced 2024-11-08 19:20:47 -05:00
Merge pull request #195 from Seanny123/memory-allocation
Memory allocation exercise
This commit is contained in:
commit
fd8bde3cd3
3 changed files with 83 additions and 0 deletions
|
@ -483,6 +483,10 @@ const exercises = [_]Exercise{
|
|||
.main_file = "095_for_loops.zig",
|
||||
.output = "1 2 4 7 8 11 13 14 16 17 19",
|
||||
},
|
||||
.{
|
||||
.main_file = "096_memory_allocation.zig",
|
||||
.output = "Running Average: 0.30 0.25 0.20 0.18 0.22",
|
||||
},
|
||||
.{
|
||||
.main_file = "999_the_end.zig",
|
||||
.output = "\nThis is the end for now!\nWe hope you had fun and were able to learn a lot, so visit us again when the next exercises are available.",
|
||||
|
|
75
exercises/096_memory_allocation.zig
Normal file
75
exercises/096_memory_allocation.zig
Normal file
|
@ -0,0 +1,75 @@
|
|||
// In most of the examples so far, the inputs are known at compile
|
||||
// time, thus the amount of memory used by the program is fixed.
|
||||
// However, if responding to input whose size is not known at compile
|
||||
// time, such as:
|
||||
// - user input via command-line arguments
|
||||
// - inputs from another program
|
||||
//
|
||||
// You'll need to request memory for your program to be allocated by
|
||||
// your operating system at runtime.
|
||||
//
|
||||
// Zig provides several different allocators. In the Zig
|
||||
// documentation, it recommends the Arena allocator for simple
|
||||
// programs which allocate once and then exit:
|
||||
//
|
||||
// const std = @import("std");
|
||||
//
|
||||
// // memory allocation can fail, so the return type is !void
|
||||
// pub fn main() !void {
|
||||
//
|
||||
// var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
|
||||
// defer arena.deinit();
|
||||
//
|
||||
// const allocator = arena.allocator();
|
||||
//
|
||||
// const ptr = try allocator.create(i32);
|
||||
// std.debug.print("ptr={*}\n", .{ptr});
|
||||
//
|
||||
// const slice_ptr = try allocator.alloc(f64, 5);
|
||||
// std.debug.print("ptr={*}\n", .{ptr});
|
||||
// }
|
||||
|
||||
// Instead of an simple integer or a constant sized slice, this
|
||||
// program requires a slice to be allocated that is the same size as
|
||||
// an input array.
|
||||
|
||||
// Given a series of numbers, take the running average. In other
|
||||
// words, each item N should contain the average of the last N
|
||||
// elements.
|
||||
|
||||
const std = @import("std");
|
||||
|
||||
fn runningAverage(arr: []const f64, avg: []f64) void {
|
||||
var sum: f64 = 0;
|
||||
|
||||
for (0.., arr) |index, val| {
|
||||
sum += val;
|
||||
avg[index] = sum / @intToFloat(f64, index + 1);
|
||||
}
|
||||
}
|
||||
|
||||
pub fn main() !void {
|
||||
// pretend this was defined by reading in user input
|
||||
var arr: []const f64 = &[_]f64{ 0.3, 0.2, 0.1, 0.1, 0.4 };
|
||||
|
||||
// initialize the allocator
|
||||
var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
|
||||
|
||||
// free the memory on exit
|
||||
defer arena.deinit();
|
||||
|
||||
// initialize the allocator
|
||||
const allocator = arena.allocator();
|
||||
|
||||
// allocate memory for this array
|
||||
var avg: []f64 = ???;
|
||||
|
||||
runningAverage(arr, avg);
|
||||
std.debug.print("Running Average: ", .{});
|
||||
for (avg) |val| {
|
||||
std.debug.print("{d:.2} ", .{val});
|
||||
}
|
||||
}
|
||||
|
||||
// For more details on memory allocation and the different types of
|
||||
// memory allocators, see https://www.youtube.com/watch?v=vHWiDx_l4V0
|
4
patches/patches/096_memory_allocation.patch
Normal file
4
patches/patches/096_memory_allocation.patch
Normal file
|
@ -0,0 +1,4 @@
|
|||
65c65
|
||||
< var avg: []f64 = ???;
|
||||
---
|
||||
> var avg: []f64 = try allocator.alloc(f64, arr.len);
|
Loading…
Reference in a new issue