@@ -19,6 +19,7 @@ has a command that does that for us. Let’s give it a shot:
1919``` bash
2020$ cd ~ /projects
2121$ cargo new guessing_game --bin
22+ Created binary (application) ` guessing_game`
2223$ cd guessing_game
2324```
2425
@@ -51,6 +52,7 @@ Let’s try compiling what Cargo gave us:
5152``` {bash}
5253$ cargo build
5354 Compiling guessing_game v0.1.0 (file:///home/you/projects/guessing_game)
55+ Finished debug [unoptimized + debuginfo] target(s) in 0.53 secs
5456```
5557
5658Excellent! Open up your ` src/main.rs ` again. We’ll be writing all of
@@ -61,6 +63,7 @@ Remember the `run` command from last chapter? Try it out again here:
6163``` bash
6264$ cargo run
6365 Compiling guessing_game v0.1.0 (file:///home/you/projects/guessing_game)
66+ Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs
6467 Running ` target/debug/guessing_game`
6568Hello, world!
6669```
@@ -282,10 +285,13 @@ we’ll get a warning:
282285``` bash
283286$ cargo build
284287 Compiling guessing_game v0.1.0 (file:///home/you/projects/guessing_game)
285- src/main.rs:10:5: 10:39 warning: unused result which must be used,
286- # [warn(unused_must_use)] on by default
287- src/main.rs:10 io::stdin ().read_line(& mut guess);
288- ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
288+ warning: unused result which must be used, # [warn(unused_must_use)] on by default
289+ --> src/main.rs:10:5
290+ |
291+ 10 | io::stdin ().read_line(& mut guess);
292+ | ^
293+
294+ Finished debug [unoptimized + debuginfo] target(s) in 0.42 secs
289295```
290296
291297Rust warns us that we haven’t used the ` Result ` value. This warning comes from
@@ -321,6 +327,7 @@ Anyway, that’s the tour. We can run what we have with `cargo run`:
321327``` bash
322328$ cargo run
323329 Compiling guessing_game v0.1.0 (file:///home/you/projects/guessing_game)
330+ Finished debug [unoptimized + debuginfo] target(s) in 0.44 secs
324331 Running ` target/debug/guessing_game`
325332Guess the number!
326333Please input your guess.
@@ -373,11 +380,12 @@ Now, without changing any of our code, let’s build our project:
373380``` bash
374381$ cargo build
375382 Updating registry ` https://github.com/rust-lang/crates.io-index`
376- Downloading rand v0.3.8
377- Downloading libc v0.1.6
378- Compiling libc v0.1.6
379- Compiling rand v0.3.8
383+ Downloading rand v0.3.14
384+ Downloading libc v0.2.17
385+ Compiling libc v0.2.17
386+ Compiling rand v0.3.14
380387 Compiling guessing_game v0.1.0 (file:///home/you/projects/guessing_game)
388+ Finished debug [unoptimized + debuginfo] target(s) in 5.88 secs
381389```
382390
383391(You may see different versions, of course.)
@@ -399,22 +407,24 @@ If we run `cargo build` again, we’ll get different output:
399407
400408``` bash
401409$ cargo build
410+ Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs
402411```
403412
404- That’s right, no output ! Cargo knows that our project has been built, and that
413+ That’s right, nothing was done ! Cargo knows that our project has been built, and that
405414all of its dependencies are built, and so there’s no reason to do all that
406415stuff. With nothing to do, it simply exits. If we open up ` src/main.rs ` again,
407- make a trivial change, and then save it again, we’ll only see one line :
416+ make a trivial change, and then save it again, we’ll only see two lines :
408417
409418``` bash
410419$ cargo build
411420 Compiling guessing_game v0.1.0 (file:///home/you/projects/guessing_game)
421+ Finished debug [unoptimized + debuginfo] target(s) in 0.45 secs
412422```
413423
414424So, we told Cargo we wanted any ` 0.3.x ` version of ` rand ` , and so it fetched the latest
415- version at the time this was written, ` v0.3.8 ` . But what happens when next
416- week, version ` v0.3.9 ` comes out, with an important bugfix? While getting
417- bugfixes is important, what if ` 0.3.9 ` contains a regression that breaks our
425+ version at the time this was written, ` v0.3.14 ` . But what happens when next
426+ week, version ` v0.3.15 ` comes out, with an important bugfix? While getting
427+ bugfixes is important, what if ` 0.3.15 ` contains a regression that breaks our
418428code?
419429
420430The answer to this problem is the ` Cargo.lock ` file you’ll now find in your
@@ -423,11 +433,11 @@ figures out all of the versions that fit your criteria, and then writes them
423433to the ` Cargo.lock ` file. When you build your project in the future, Cargo
424434will see that the ` Cargo.lock ` file exists, and then use that specific version
425435rather than do all the work of figuring out versions again. This lets you
426- have a repeatable build automatically. In other words, we’ll stay at ` 0.3.8 `
436+ have a repeatable build automatically. In other words, we’ll stay at ` 0.3.14 `
427437until we explicitly upgrade, and so will anyone who we share our code with,
428438thanks to the lock file.
429439
430- What about when we _ do_ want to use ` v0.3.9 ` ? Cargo has another command,
440+ What about when we _ do_ want to use ` v0.3.15 ` ? Cargo has another command,
431441` update ` , which says ‘ignore the lock, figure out all the latest versions that
432442fit what we’ve specified. If that works, write those versions out to the lock
433443file’. But, by default, Cargo will only look for versions larger than ` 0.3.0 `
@@ -510,13 +520,15 @@ Try running our new program a few times:
510520``` bash
511521$ cargo run
512522 Compiling guessing_game v0.1.0 (file:///home/you/projects/guessing_game)
523+ Finished debug [unoptimized + debuginfo] target(s) in 0.55 secs
513524 Running ` target/debug/guessing_game`
514525Guess the number!
515526The secret number is: 7
516527Please input your guess.
5175284
518529You guessed: 4
519530$ cargo run
531+ Finished debug [unoptimized + debuginfo] target(s) in 0.0 secs
520532 Running ` target/debug/guessing_game`
521533Guess the number!
522534The secret number is: 83
@@ -618,15 +630,20 @@ I did mention that this won’t quite compile yet, though. Let’s try it:
618630``` bash
619631$ cargo build
620632 Compiling guessing_game v0.1.0 (file:///home/you/projects/guessing_game)
621- src/main.rs:28:21: 28:35 error: mismatched types:
622- expected ` & collections::string::String`
623- found ` & _`
624- (expected struct ` collections::string::String`
625- found integral variable) [E0308]
626- src/main.rs:28 match guess.cmp(& secret_number) {
627- ^~~~~~~~~~~~~~
633+ error[E0308]: mismatched types
634+ --> src/main.rs:23:21
635+ |
636+ 23 | match guess.cmp(& secret_number) {
637+ | ^^^^^^^^^^^^^^ expected struct ` std::string::String`
638+ |
639+ = note: expected type ` & std::string::String`
640+ = note: found type ` & {integer}`
641+
628642error: aborting due to previous error
629- Could not compile ` guessing_game`
643+
644+ error: Could not compile ` guessing_game`
645+
646+ To learn more, run the command again with --verbose.
630647` ` `
631648
632649Whew! This is a big error. The core of it is that we have ‘mismatched types’.
@@ -722,6 +739,7 @@ Let’s try our program out!
722739` ` ` bash
723740$ cargo run
724741 Compiling guessing_game v0.1.0 (file:///home/you/projects/guessing_game)
742+ Finished debug [unoptimized + debuginfo] target(s) in 0.57 secs
725743 Running ` target/guessing_game`
726744Guess the number!
727745The secret number is: 58
@@ -785,6 +803,7 @@ and quit. Observe:
785803` ` `
786804$ cargo run
787805 Compiling guessing_game v0.1.0 (file:///home/you/projects/guessing_game)
806+ Finished debug [unoptimized + debuginfo] target(s) in 0.58 secs
788807 Running ` target/guessing_game`
789808Guess the number!
790809The secret number is: 59
@@ -919,6 +938,7 @@ Now we should be good! Let’s try:
919938```bash
920939$ cargo run
921940 Compiling guessing_game v0.1.0 (file:///home/you/projects/guessing_game)
941+ Finished debug [unoptimized + debuginfo] target(s) in 0.57 secs
922942 Running `target/guessing_game`
923943Guess the number!
924944The secret number is: 61
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