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RangeX

Limitations of 'for' loop in Zig

  • (start..end) only support usize type, and step only 1, no backward. Only exclusive.

  • Do not support customized range to keep the language simple

Pros of 'for' loop in Zig

  • Can iterate multiple ranges together, avoid the usage of dedicated indexed range:
// Reduce: Sum all elements, have to specify T, can't use 'anytype'
fn reduceSum(comptime T: type, arr: []const T) @TypeOf(arr[0]) {
    var sum: @TypeOf(arr[0]) = 0;
    for (arr) |item| {
        sum += item;
    }
    return sum;
}

test "over array inclusively with generated index" {
    const array = [_]i32{ 1, 2, 3, 4, 5 };
    var s: i32 = 0;
    for (0.., array, 1..array.len + 1) |index, item, verify| {
        s += item;
        try std.testing.expectEqual(array[index], item);
        try std.testing.expectEqual(item, @as(@TypeOf(array[0]), @intCast(verify)));
    }
    try std.testing.expectEqual(s, reduceSum(@TypeOf(array[0]), &array));
    try std.testing.expectEqual(s, reduceSum(@TypeOf(array[0]), array[0..]));
}

while range is flexible enough

Usage:

1. Add dependent as submodule or just clone within src

git submodule add -f --name rangex https://github.com/PegasusPlusUS/rangex-zig.git src/external/while_rangex

or

git clone https://github.com/PegasusPlusUS/rangex-zig.git src/external/while_rangex

2. Add AnonymousImport in build graph to facilitate @import

// in build.zig
pub fn build(b: *std.Build) void {
    //...
    //...
    //...

    // lib target
    const lib = b.addStaticLibrary(.{
        .name = "my_zig_lib",
        // In this case the main source file is merely a path, however, in more
        // complicated build scripts, this could be a generated file.
        .root_source_file = b.path("src/root.zig"),
        .target = target,
        .optimize = optimize,
    });
    // add anonymous import to facilitate import in exe source files, if cross imported,
    // both should add anonymous import
    lib.root_module.addAnonymousImport("while_rangex", .{
        .root_source_file = b.path("src/external/while_rangex/src/root.zig"),
    });

    // exe target
    const exe = b.addExecutable(.{
        .name = "my_zig_executable",
        .root_source_file = b.path("src/main.zig"),
        .target = target,
        .optimize = optimize,
    });
    // add anonymous import to facilitate import in exe source files, if cross imported,
    // both should add anonymous import
    exe.root_module.addAnonymousImport("while_rangex", .{
        .root_source_file = b.path("src/external/while_rangex/src/root.zig"),
    });
    exe.linkLibrary(lib_while_rangex);
}

import at src

// in src/main.cpp
// Use anonymous import instead, can only use one way, to avoid symbol redefinition.
// const while_rangex = @import("external/while_rangex/src/root.zig").WhileRange;
const while_rangex = @import("while_rangex").WhileRange;

fn main() !void {
    var sum:usize = 0;
    var accumulate_range = try while_rangex(usize).init(1, 100, true, 1);
    while (accumulate_range.next()) |n| {
        sum += n;
    }
    std.debug.print("Accumulate from {} to {} result in:{}", .{1, 100, sum});
}

View test cases for all possiblities

// in src/external/while_rangex/src/root.zig
// main() and test cases in while_rangex library:
pub fn main() !void {
    // Integer range (forward)
    var range1 = try WhileRange(i32).init(0, 10, false, 2);
    std.debug.print("Forward exclusive int range [0, 10) by 2:\n", .{});
    while (range1.next()) |value| {
        std.debug.print("{} ", .{value});
    }
    std.debug.print("\n\n", .{});

    // Integer range (backward)
    var range2 = try WhileRange(i32).init(10, 0, false, -3);
    std.debug.print("Backward exclusive int range [10, 0) by -3:\n", .{});
    while (range2.next()) |value| {
        std.debug.print("{} ", .{value});
    }
    std.debug.print("\n\n", .{});

    // Float range
    var range3 = try WhileRange(f32).init(0.0, 1.0, false, 0.2);
    std.debug.print("Float exclusive range [0.0, 1.0) by 0.2:\n", .{});
    while (range3.next()) |value| {
        std.debug.print("{d:.1} ", .{value});
    }
    std.debug.print("\n\n", .{});

    var range4 = try WhileRange(f32).init(1.0, 0.0, false, -0.2);
    std.debug.print("Backward float exclusive range [1.0, 0.0) by -0.2:\n", .{});
    while (range4.next()) |value| {
        std.debug.print("{d:.1} ", .{value});
    }
    std.debug.print("\n", .{});
}

test "std u8 start stop exclusive step is 1" {
    // Integer range (forward)
    var s: u16 = 0;
    var range1 = try WhileRange(u8).init(1, 101, false, 1);
    while (range1.next()) |value| {
        s += value;
    }
    try std.testing.expectEqual(s, 5050);
}

test "std u8 start stop backward exclusive step is -1" {
    // Integer range (forward)
    var s: u16 = 0;
    var range1 = try WhileRange(u8).init(100, 0, false, -1);
    while (range1.next()) |value| {
        s += value;
    }
    try std.testing.expectEqual(s, 5050);
}

test "std u8 start stop backward inclusive step is -1" {
    // Integer range (forward)
    var s: u16 = 0;
    var range1 = try WhileRange(u8).init(100, 1, true, -1);
    while (range1.next()) |value| {
        s += value;
    }
    try std.testing.expectEqual(s, 5050);
}

test "std u8 start stop inclusive step is 1" {
    // Integer range (forward)
    var s: u16 = 0;
    var range1 = try WhileRange(u8).init(1, 100, true, 1);
    while (range1.next()) |value| {
        s += value;
    }
    try std.testing.expectEqual(s, 5050);
}

test "std u8 start stop exclusive step is 2" {
    // Integer range (forward)
    var s: u16 = 0;
    var range1 = try WhileRange(u8).init(1, 101, false, 2);
    while (range1.next()) |value| {
        s += value;
    }
    try std.testing.expectEqual(s, (1 + 99) * 50 / 2);
}

test "std u8 start stop inclusive step is 2" {
    // Integer range (forward)
    var s: u16 = 0;
    var range1 = try WhileRange(u8).init(1, 101, true, 2);
    while (range1.next()) |value| {
        s += value;
    }
    try std.testing.expectEqual(s, (1 + 101) * 51 / 2);
}

test "std u8 start stop ex/inclusive step is 2 stop not on step" {
    // Integer range (forward)
    var s_e: u16 = 0;
    var range_e = try WhileRange(u8).init(1, 100, false, 2);
    while (range_e.next()) |value| {
        s_e += value;
    }
    var s_i: u16 = 0;
    var range_i = try WhileRange(u8).init(1, 100, true, 2);
    while (range_i.next()) |value| {
        s_i += value;
    }
    try std.testing.expectEqual(s_e, (1 + 99) * 50 / 2);
    try std.testing.expectEqual(s_i, s_e);
}

test "std u8 start stop backward exclusive step is -2 stop not on step" {
    // Integer range (forward)
    var s_e: u16 = 0;
    var range_e = try WhileRange(u8).init(100, 1, false, -2);
    while (range_e.next()) |value| {
        s_e += value;
    }
    var s_i: u16 = 0;
    var range_i = try WhileRange(u8).init(100, 1, true, -2);
    while (range_i.next()) |value| {
        s_i += value;
    }
    try std.testing.expectEqual(s_e, (100 + 2) * 50 / 2);
    try std.testing.expectEqual(s_i, s_e);
}

test "std u8 start stop ex/inclusive empty range" {
    // Integer range (forward)
    var s_e: u16 = 0;
    var range_e = try WhileRange(u8).init(1, 0, false, 2);
    while (range_e.next()) |value| {
        s_e += value;
    }
    try std.testing.expectEqual(s_e, 0);

    var s_i: u16 = 0;
    var range_i = try WhileRange(u8).init(1, 0, true, 2);
    while (range_i.next()) |value| {
        s_i += value;
    }
    try std.testing.expectEqual(s_i, 0);
}

test "std i8 start stop ex/inclusive empty range" {
    // Integer range (forward)
    var s_e: i16 = 0;
    var range_e = try WhileRange(i8).init(0, 1, false, -2);
    while (range_e.next()) |value| {
        s_e += value;
    }
    try std.testing.expectEqual(s_e, 0);

    var s_i: i16 = 0;
    var range_i = try WhileRange(i8).init(0, 1, true, -2);
    while (range_i.next()) |value| {
        s_i += value;
    }
    try std.testing.expectEqual(s_i, 0);
}

test "std f32 start stop ex/inclusive step is 0.2" {
    var s_e: f32 = 0;
    var range_e = try WhileRange(f32).init(0.0, 1.0, false, 0.2);
    while (range_e.next()) |value| {
        s_e += value;
    }
    try std.testing.expectEqual(s_e, (0.0 + 0.8) * 5 / 2);

    var s_i: f32 = 0;
    var range_i = try WhileRange(f32).init(0.0, 1.0, true, 0.2);
    while (range_i.next()) |value| {
        s_i += value;
    }
    try std.testing.expectEqual(s_i, (0.0 + 1.0) * 6 / 2);
}

test "std f32 start stop backward exclusive step is -0.2" {
    var s_e: f32 = 0;
    var range_e = try WhileRange(f32).init(0.8, -0.2, false, -0.2);
    while (range_e.next()) |value| {
        //std.debug.print("{d:.1} ", .{value});
        s_e += value;
    }

    // Use approxEqAbs or approxEqRel for float comparison
    try std.testing.expectApproxEqAbs(s_e, (0.8 + 0.0) * 5 / 2, 1e-6);

    var s_i: f32 = 0;
    var range_i = try WhileRange(f32).init(1.0, 0.0, true, -0.2);
    while (range_i.next()) |value| {
        s_i += value;
    }
    try std.testing.expectApproxEqAbs(s_i, (1.0 + 0.0) * 6 / 2, 1e-6);
}

test "indexed while range" {
    var index :usize = 0;
    var range = try IndexedWhileRange(u8).init(10, 1, true, -1);
    std.debug.print("Indexed backward u8 while range [10, 1]:\n", .{});
    std.debug.print("(Index:Value)", .{});
    while (range.next()) |element| {
        try std.testing.expectEqual(index, element.index);
        index += 1;
        std.debug.print("({}:{})\n", .{element.index, element.value});
    }
    std.debug.print("\n", .{});
}