mirror of
https://github.com/ratfactor/ziglings
synced 2024-05-05 01:56:03 +02:00
79 lines
2.4 KiB
Zig
79 lines
2.4 KiB
Zig
//
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// In most of the examples so far, the inputs are known at compile
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// time, thus the amount of memory used by the program is fixed.
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// However, if responding to input whose size is not known at compile
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// time, such as:
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// - user input via command-line arguments
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// - inputs from another program
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//
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// You'll need to request memory for your program to be allocated by
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// your operating system at runtime.
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//
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// Zig provides several different allocators. In the Zig
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// documentation, it recommends the Arena allocator for simple
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// programs which allocate once and then exit:
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//
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// const std = @import("std");
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//
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// // memory allocation can fail, so the return type is !void
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// pub fn main() !void {
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//
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// var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
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// defer arena.deinit();
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//
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// const allocator = arena.allocator();
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//
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// const ptr = try allocator.create(i32);
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// std.debug.print("ptr={*}\n", .{ptr});
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//
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// const slice_ptr = try allocator.alloc(f64, 5);
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// std.debug.print("slice_ptr={*}\n", .{slice_ptr});
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// }
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// Instead of a simple integer or a constant sized slice, this
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// program requires a slice to be allocated that is the same size as
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// an input array.
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// Given a series of numbers, take the running average. In other
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// words, each item N should contain the average of the last N
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// elements.
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const std = @import("std");
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fn runningAverage(arr: []const f64, avg: []f64) void {
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var sum: f64 = 0;
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for (0.., arr) |index, val| {
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sum += val;
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const f_index: f64 = @floatFromInt(index + 1);
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avg[index] = sum / f_index;
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}
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}
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pub fn main() !void {
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// pretend this was defined by reading in user input
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var arr: []const f64 = &[_]f64{ 0.3, 0.2, 0.1, 0.1, 0.4 };
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// initialize the allocator
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var arena = std.heap.ArenaAllocator.init(std.heap.page_allocator);
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// free the memory on exit
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defer arena.deinit();
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// initialize the allocator
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const allocator = arena.allocator();
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// allocate memory for this array
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var avg: []f64 = ???;
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runningAverage(arr, avg);
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std.debug.print("Running Average: ", .{});
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for (avg) |val| {
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std.debug.print("{d:.2} ", .{val});
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}
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std.debug.print("\n", .{});
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}
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// For more details on memory allocation and the different types of
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// memory allocators, see https://www.youtube.com/watch?v=vHWiDx_l4V0
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