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| -rw-r--r-- | build.zig | 4 | ||||
| -rw-r--r-- | exercises/076a_memory_allocation.zig | 70 |
2 files changed, 74 insertions, 0 deletions
@@ -393,6 +393,10 @@ const exercises = [_]Exercise{ .output = "Array:123056. Many-item pointer:123.", }, .{ + .main_file = "076a_memory_allocation.zig", + .output = "Running Average: 0.30 0.25 0.20 0.18 0.22", + }, + .{ .main_file = "077_sentinels2.zig", .output = "Weird Data!", }, diff --git a/exercises/076a_memory_allocation.zig b/exercises/076a_memory_allocation.zig new file mode 100644 index 0000000..b098773 --- /dev/null +++ b/exercises/076a_memory_allocation.zig @@ -0,0 +1,70 @@ +// 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 and is requested. 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 you 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 because your computer is out of memory, 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.create(i32); +// std.debug.print("ptr={*}\n", .{ptr}); +// } + +// Instead of a simple integer, 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, the running 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 (TODO: replace this with ???) + const allocator = arena.allocator(); + + // TODO: replace this whole line with ??? + var avg = try allocator.alloc(f64, arr.len); + + 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 |