diff options
| -rw-r--r-- | build.zig | 4 | ||||
| -rw-r--r-- | exercises/060_floats.zig | 91 | ||||
| -rw-r--r-- | patches/patches/060_floats.patch | 4 |
3 files changed, 99 insertions, 0 deletions
@@ -306,6 +306,10 @@ const exercises = [_]Exercise{ .main_file = "059_integers.zig", .output = "Zig is cool.", }, + .{ + .main_file = "060_floats.zig", + .output = "Shuttle liftoff weight: 1995796kg", + }, }; /// Check the zig version to make sure it can compile the examples properly. diff --git a/exercises/060_floats.zig b/exercises/060_floats.zig new file mode 100644 index 0000000..6ff7b50 --- /dev/null +++ b/exercises/060_floats.zig @@ -0,0 +1,91 @@ +// +// Zig has support for IEEE-754 floating-point numbers in these +// specific sizes: f16, f32, f64, f128. Floating point literals +// may be writen in scientific notation: +// +// const a1: f32 = 1200.0; // 1,200 +// const a2: f32 = 1.2e+3; // 1,200 +// const b1: f32 = -500_000.0; // -500,000 +// const b2: f32 = -5.0e+5; // -500,000 +// +// Hex floats can't use the letter 'e' because that's a hex +// digit, so we use a 'p' instead: +// +// const hex: f16 = 0x2A.F7p+3; // Wow, that's arcane! +// +// Be sure to use a float type that is large enough to store your +// value (both in terms of significant digits and scale). +// Rounding may or may not be okay, but numbers which are too +// large or too small become inf or -inf (positive or negative +// infinity)! +// +// const pi: f16 = 3.1415926535; // rounds to 3.140625 +// const av: f16 = 6.02214076e+23; // Avogadro's inf(inity)! +// +// A float literal has a decimal point. When performing math +// operations with numeric literals, ensure the types match. Zig +// does not perform unsafe type coercions behind your back: +// +// var foo: f16 = 13.5 * 5; // ERROR! +// var foo: f16 = 13.5 * 5.0; // No problem, both are floats +// +// Please fix the two float problems with this program and +// display the result as a whole number. + +const print = @import("std").debug.print; + +pub fn main() void { + // The approximate weight of the Space Shuttle upon liftoff + // (including boosters and fuel tank) was 2,200 tons. + // + // We'll convert this weight from tons to kilograms at a + // conversion of 907.18kg to the ton. + var shuttle_weight: f16 = 907.18 * 2200; + + // By default, float values are formatted in scientific + // notation. Try experimenting with '{d}' and '{d:.3}' to see + // how decimal formatting works. + print("Shuttle liftoff weight: {d:.0}kg\n", .{shuttle_weight}); +} + +// Floating further: +// +// As an example, Zig's f16 is a IEEE 754 "half-precision" binary +// floating-point format ("binary16"), which is stored in memory +// like so: +// +// 0 1 0 0 0 0 1 0 0 1 0 0 1 0 0 0 +// | |-------| |-----------------| +// | exponent significand +// | +// sign +// +// This example is the decimal number 3.140625, which happens to +// be the closest representation of Pi we can make with an f16 +// due to the way IEEE-754 floating points store digits: +// +// * Sign bit 0 makes the number positive. +// * Exponent bits 10000 are a scale of 16. +// * Significand bits 1001001000 are the decimal value 584. +// +// IEEE-754 saves space by modifying these values: the value +// 01111 is always subtracted from the exponent bits (in our +// case, 10000 - 01111 = 1, so our exponent is 2^1) and our +// significand digits become the decimal value _after_ an +// implicit 1 (so 1.1001001000 or 1.5703125 in decimal)! This +// gives us: +// +// 2^1 * 1.5703125 = 3.140625 +// +// Feel free to forget these implementation details immediately. +// The important thing to know is that floating point numbers are +// great at storing big and small values (f64 lets you work with +// numbers on the scale of the number of atoms in the universe), +// but digits may be rounded, leading to results which are less +// precise than integers. +// +// Fun fact: sometimes you'll see the significand labeled as a +// "mantissa" but Donald E. Knuth says not to do that. +// +// C compatibility fact: There is also a Zig floating point type +// specifically for working with C ABIs called c_longdouble. diff --git a/patches/patches/060_floats.patch b/patches/patches/060_floats.patch new file mode 100644 index 0000000..d20986e --- /dev/null +++ b/patches/patches/060_floats.patch @@ -0,0 +1,4 @@ +43c43 +< var shuttle_weight: f16 = 907.18 * 2200; +--- +> var shuttle_weight: f32 = 907.18 * 2200.0; |