From 78d191cbf396d2ea32d920282934aa44f8ade4be Mon Sep 17 00:00:00 2001
From: Nic Gaffney <gaffney_nic@protonmail.com>
Date: Mon, 20 Oct 2025 01:59:56 -0500
Subject: inital commit

---
 src/lib.zig  | 73 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/main.zig | 33 +++++++++++++++++++++++++++
 2 files changed, 106 insertions(+)
 create mode 100644 src/lib.zig
 create mode 100644 src/main.zig

(limited to 'src')

diff --git a/src/lib.zig b/src/lib.zig
new file mode 100644
index 0000000..8e99ad3
--- /dev/null
+++ b/src/lib.zig
@@ -0,0 +1,73 @@
+const std = @import("std");
+
+/// Compose two single argument functions
+pub fn compose(
+    comptime outerFunc: anytype,
+    comptime innerFunc: anytype
+) blk:{
+    const outerFuncType = @TypeOf(outerFunc);
+    const outerFuncTypeInfo = @typeInfo(outerFuncType);
+    if(outerFuncTypeInfo != .@"fn")
+        @compileError("Expected function, found " ++ @typeName(outerFuncType));
+    const innerFuncType = @TypeOf(innerFunc);
+    const innerFuncTypeInfo = @typeInfo(innerFuncType);
+    if(innerFuncTypeInfo != .@"fn")
+        @compileError("Expected function, found " ++ @typeName(innerFuncType));
+    const out = @typeInfo(@TypeOf(outerFunc)).@"fn".return_type.?;
+    const in = @typeInfo(@TypeOf(innerFunc)).@"fn".params[0].type.?;
+    break :blk fn(in) out;
+} {
+    const out = @typeInfo(@TypeOf(outerFunc)).@"fn".return_type.?;
+    const in = @typeInfo(@TypeOf(innerFunc)).@"fn".params[0].type.?;
+    return struct {
+        fn func(input: in) out {
+            return outerFunc(innerFunc(input));
+        }
+    }.func;
+}
+
+pub fn mapAlloc(
+    allocator: std.mem.Allocator,
+    func: anytype,
+    items: anytype,
+) error{OutOfMemory}!blk:{
+    const itemsType = @TypeOf(items);
+    const itemsTypeInfo = @typeInfo(itemsType);
+    const funcType = @TypeOf(func);
+    const funcTypeInfo = @typeInfo(funcType);
+    if(funcTypeInfo != .@"fn")
+        @compileError("Expected function, found " ++ @typeName(funcType));
+    if(itemsTypeInfo != .array and itemsTypeInfo != .pointer) {
+        @compileError("Expected array or slice, found " ++ @typeName(itemsType));
+    }
+
+    break :blk []funcTypeInfo.@"fn".return_type.?;
+} {
+    const funcType = @TypeOf(func);
+    const funcTypeInfo = @typeInfo(funcType);
+    var result = try allocator.alloc(funcTypeInfo.@"fn".return_type.?, items.len);
+    for(items, 0..) |item, i|
+        result[i] = func(item);
+    return result;
+}
+
+pub fn map(
+    func: anytype,
+    items: anytype,
+    buffer: anytype,
+) void {
+    const funcType = @TypeOf(func);
+    const bufferType = @TypeOf(buffer);
+    const itemsType = @TypeOf(items);
+    const funcTypeInfo = @typeInfo(funcType);
+    const bufferTypeInfo = @typeInfo(bufferType);
+    const itemsTypeInfo = @typeInfo(itemsType);
+    if(funcTypeInfo != .@"fn")
+        @compileError("Expected function, found " ++ @typeName(funcType));
+    if(itemsTypeInfo != .array and itemsTypeInfo != .pointer)
+        @compileError("Expected array, found " ++ @typeName(itemsType));
+    if(bufferTypeInfo != .array and bufferTypeInfo != .pointer)
+        @compileError("Expected array, found " ++ @typeName(bufferType));
+    for (items, 0..) |item, i|
+        buffer.*[i] = func(item);
+}
diff --git a/src/main.zig b/src/main.zig
new file mode 100644
index 0000000..949c368
--- /dev/null
+++ b/src/main.zig
@@ -0,0 +1,33 @@
+const std = @import("std");
+const func = @import("funcz");
+
+fn iter(n: i32) i32 {
+    return n + 1;
+}
+
+fn mul2(n: i32) i32 {
+    return n * 2;
+}
+
+pub fn main() !void {
+    var gpa = std.heap.DebugAllocator(.{}){};
+    const allocator = gpa.allocator();
+    const iterThenMul2 = func.compose(mul2, iter);
+    var items = [_]i32{ 0, 1, 2, 3, 4 };
+    const itemsSlice: []i32 = items[0..items.len];
+    const newItems = try func.mapAlloc(allocator, iterThenMul2, itemsSlice);
+    defer allocator.free(newItems);
+    var buffer: [128]i32 = undefined;
+    func.map(iterThenMul2, itemsSlice, &buffer);
+    std.debug.print("compose(mul2, iter)(5) = {d}\n", .{ iterThenMul2(5) });
+    std.debug.print("mapAlloc(allocator, compose(mul2, iter), []i32{{ 0, 1, 2, 3, 4 }}) = {{ ", .{});
+    for(newItems) |item| {
+        std.debug.print("{d}, ", .{item});
+    }
+    std.debug.print("}}\n", .{});
+    std.debug.print("map(compose(mul2, iter), []i32{{ 0, 1, 2, 3, 4 }}, &buffer) = {{ ", .{});
+    for(buffer[0..items.len]) |item| {
+        std.debug.print("{d}, ", .{item});
+    }
+    std.debug.print("}}\n", .{});
+}
-- 
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