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//! By convention, root.zig is the root source file when making a library. If
//! you are making an executable, the convention is to delete this file and
//! start with main.zig instead.
const std = @import("std");
const builtin = @import("builtin");
const testing = std.testing;
// Read the following article to understand the NaN-packing strategy:
//
// https://tkammer.de/zisp/notes/nan.html
//
// Note: Packed structs are least-to-most significant, so the order of fields
// must be reversed relative to a typical big-endian illustration of the bit
// patterns of IEEE 754 double-precision floating point numbers.
const Value = packed union {
double: f64,
nan: packed struct {
rest: u51,
quiet: u1,
exp: u11,
sign: u1,
},
int: packed struct {
code: u51,
neg: bool,
exp: u11,
is_int: bool,
},
pointer: packed struct {
value: u48,
type: u3,
_zo: u1,
_qnan: u12,
},
};
// Helpers
inline fn zisp_dump(v: Value) void {
std.debug.dumpHex(std.mem.asBytes(&v));
}
///! Checks for any IEEE 754 NaN.
inline fn zisp_is_nan(v: Value) bool {
return v.nan.exp == std.math.maxInt(u11);
}
///! Checks for a Zisp value packed into a NaN.
inline fn zisp_is_packed(v: Value) bool {
return zisp_is_nan(v) and v.nan.rest != 0;
}
///! Checks for a regular double including infinity or canonical NaN
inline fn zisp_is_double(v: Value) bool {
return !zisp_is_packed(v);
}
inline fn zisp_assert_double(v: Value) void {
if (!zisp_is_double(v)) {
zisp_dump(v);
@panic("not double");
}
}
inline fn zisp_is_int(v: Value) bool {
return zisp_is_packed(v) and v.int.is_int;
}
inline fn zisp_assert_int(v: Value) void {
if (!zisp_is_int(v)) {
zisp_dump(v);
@panic("not int");
}
}
// See detailed NaN packing docs for why the +/- 1.
const zisp_int_min = std.math.minInt(i52) + 1;
const zisp_int_max = std.math.maxInt(i52) - 1;
inline fn zisp_assert_int_range(int: i64) void {
if (int < zisp_int_min) {
std.debug.print("int to pack is too small: {}", .{int});
@panic("int to pack is too small");
}
if (int > zisp_int_max) {
std.debug.print("int to pack is too large: {}", .{int});
@panic("int to pack is too large");
}
}
inline fn zisp_int_pack_neg(int: i64) Value {
return @bitCast(int);
}
inline fn zisp_int_unpack_neg(v: Value) i64 {
return @bitCast(v);
}
const zisp_int_pos_mask: u64 = 0xfff7ffffffffffff;
inline fn zisp_int_pack_pos(int: i64) Value {
const uint: u64 = @bitCast(int);
return @bitCast(uint ^ zisp_int_pos_mask);
}
inline fn zisp_int_unpack_pos(v: Value) i64 {
const uint: u64 = @bitCast(v);
return @bitCast(uint ^ zisp_int_pos_mask);
}
inline fn zisp_int_pack(int: i64) Value {
zisp_assert_int_range(int);
if (int < 0) {
return zisp_int_pack_neg(int);
} else {
return zisp_int_pack_pos(int);
}
}
inline fn zisp_int_unpack(v: Value) i64 {
zisp_assert_int(v);
if (v.int.neg) {
return zisp_int_unpack_neg(v);
} else {
return zisp_int_unpack_pos(v);
}
}
// Doubles
pub fn zisp_double(d: f64) Value {
return @bitCast(d);
}
// pub fn zisp_double_p(v: Value) Value {
// return zisp_bool(zisp_is_double(v));
// }
pub fn zisp_double_get(v: Value) f64 {
zisp_assert_double(v);
return v.double;
}
pub fn zisp_double_add(v1: Value, v2: Value) Value {
const d1 = zisp_double_get(v1);
const d2 = zisp_double_get(v2);
return zisp_double(d1 + d2);
}
// Ints
pub fn zisp_int(int: i64) Value {
return zisp_int_pack(int);
}
// pub fn zisp_int_p(v: Value) Value {
// return zisp_bool(zisp_is_int(v));
// }
pub fn zisp_int_get(v: Value) i64 {
return zisp_int_unpack(v);
}
pub fn zisp_int_add(v1: Value, v2: Value) Value {
const int1 = zisp_int_get(v1);
const int2 = zisp_int_get(v2);
return zisp_int(int1 + int2);
}
// Tests
test "double add functionality" {
const d1: f64 = 0.123456789;
const d2: f64 = -0.987654321;
const v1 = zisp_double(d1);
const v2 = zisp_double(d2);
const v3 = zisp_double_add(v1, v2);
const result = zisp_double_get(v3);
try std.testing.expect(result == d1 + d2);
}
test "int add functionality" {
const int1: i64 = 123456789;
const int2: i64 = -987654321;
const v1 = zisp_int(int1);
const v2 = zisp_int(int2);
const v3 = zisp_int_add(v1, v2);
const result = zisp_int_get(v3);
try std.testing.expect(result == int1 + int2);
}
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