forked from dessy/ladieslearningcode-ruby
-
Notifications
You must be signed in to change notification settings - Fork 0
Expand file tree
/
Copy pathrubywow.html
More file actions
1458 lines (1321 loc) · 50.3 KB
/
rubywow.html
File metadata and controls
1458 lines (1321 loc) · 50.3 KB
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
<!DOCTYPE html>
<html>
<head>
<title>Ladies Learning Ruby</title>
<meta charset='utf-8'>
<script src='default.js'></script>
</head>
<style>
</style>
<body style='display: none'>
<section class='slides layout-regular template-default'>
<img src='images/ladieslearningcode-125x125.gif'>
<article>
<h1>
Learning to Program
<br>
with Ruby
</h1>
<p>
Dessy Daskalov
<br>
@dess_e
</p>
</article>
<article id="what-is-ruby">
<style>
#what-is-ruby p { margin: 100px 0px; font-size: 40px; line-height: 50px; };
</style>
<h3>
What is Ruby?
</h3>
<p />
<div class="build">
<p class='large-font'>Ruby is a programming language.</p>
<p class='large-font'>Wait ... what's a programming language?</p>
<p class='large-font'>Let's backtrack a bit.</p>
</div>
</article>
<article id='two-things'>
<style>
#two-things p { margin: 200px 0px; }
</style>
<p class='large-font'>There are two things you should know about your computer.</p>
</article>
<article id='computer-wishes'>
<style>
#computer-wishes h3 { padding-bottom: 10px; }
#computer-wishes img { margin-left: 70px; }
</style>
<h3>
1. Your computer speaks a different language.
</h3>
<p>This is how your computer wishes you could speak to it:</p>
<p />
<img src="images/machine-language.jpg" width="600" height="411" border="1">
</article>
<article>
<h3>
This is where a programming language comes in.
</h3>
<p>A programming language is a language that is relatively easy for you to learn, but can also be understood by the computer.</p>
<p>It's the middle ground between English and the language that the computer understands.</p>
</article>
<article id='stupid-computer'>
<style>
#stupid-computer p { margin: 200px 0px; }
</style>
<h3>
2. Your computer is not very smart.
</h3>
<p class='large-font'>Your computer can only do what you tell it to if you give it exact instructions.</p>
</article>
<article>
<h3>People vs. Computers</h3>
<p>
Suppose you had to teach a person how to make a peanut butter sandwich.
You might give the person an easy to follow recipe.
</p>
<p>1. Toast two slices of bread</p>
<p>2. Spread peanut butter on one slice of bread</p>
<p>3. Spread jam on the other slice of bread</p>
<p>4. Put the two pieces of bread together</p>
<p>5. Put the sandwich on a plate and serve it</p>
</article>
<article>
<h3>People understand GENERAL instructions.</h3>
<p>
We left out some parts of the process, but a person could figure out:
</p>
<p>Where to find the ingredients</p>
<p>To use a butter knife to spread the peanut butter</p>
<p>To put the bread in a toaster in order to toast it</p>
<p>etc, etc, etc (there are many little steps)</p>
</article>
<article id='computers-exact'>
<style>
#computers-exact p { margin: 150px 0px; };
</style>
<h3>Computers understand EXACT instructions.</h3>
<p class='large-font'>
This same recipe for a computer would be much, much longer.
</p>
</article>
<article>
<h3>1. Toast two slices of bread</h3>
<p>What is bread?</p>
<p>Where is it found?</p>
<p>How do I open the bag?</p>
<p>What is a slice?</p>
<p>How do I slice the bread?</p>
<p>How do I "toast"?</p>
<p>What is a toaster?</p>
<p>How do I use a toaster?</p>
<p>etc, etc, etc</p>
</article>
<article>
<h3>2. Spread peanut butter on one slice of bread</h3>
<p>What is peanut butter?</p>
<p>How do I "spread" peanut butter?</p>
<p>What is a butter knife?</p>
<p>Where is it found?</p>
<p>How do I open the knife drawer?</p>
<p>Which slice do I spread it on?</p>
<p>How much peanut butter do I spread?</p>
<p>etc, etc, etc</p>
</article>
<article id='programming-languages'>
<style>
#programming-languages p { margin-top: 80px; }
#programming-languages .mixed-font { line-height: 50px; }
#programming-languages b { font-size: 40px; }
</style>
<h3>Back to programming languages.</h3>
<p>A programming language makes it easier for you to give the computer instructions.</p>
<p class='mixed-font'>
It's made up of <b>simple elements</b>, that when <b>combined together</b>,
are used to write a set of <b>instructions</b> that the computer then breaks down and interprets as its own language.
</p>
</article>
<article id='learned-programming'>
<style>
#learned-programming p { margin-top: 100px; }
</style>
<h3>
You've just learned what programming is!
</h3>
<p class='large-font'>Programming is writing out <b>exact instructions</b> that your computer can follow to do things.</p>
</article>
<article id='ruby-rocks'>
<style>
#ruby-rocks .large-font { margin: 50px; }
</style>
<h3>
Why Ruby Rocks!
</h3>
<p>Created in 1993 by Yukihiro Matsumoto, from Japan.</p>
<p class='large-font'>
"I hope to see Ruby help every programmer in the world to be productive, and to enjoy programming, and to be happy.
That is the primary purpose of the Ruby language."
</p>
<p>Ruby is <b>fun</b>, it's <b>easy to learn</b>, and the <b>syntax is very forgiving</b>.</p>
</article>
<article>
<p class='large-font'>This is some code in Java:</p>
<section>
<pre>
class Person {
private String name, int age;
public void setName(String name) {
this.name = name;
}
public String getName() {
return name;
}
public void setAge(int age) {
this.age = age;
}
public String getAge() {
return age;
}
}</pre>
</section>
</article>
<article>
<p class='large-font'>The equivalent code in Ruby looks like this:</p>
<section>
<pre>
class Person
attr_accessor :name, :age
end
</pre>
</section>
</article>
<article id='irb-intro'>
<style>
#irb-intro .instructions { margin-top: 100px; }
</style>
<h3>
Time to see Ruby in action!
</h3>
<p>IRB is like text messaging with Ruby.</p>
<p>You'll ask Ruby to do something, and it will respond.</p>
<div class='instructions'>
<p><b>OS X</b></p>
<section>
<pre>Applications -> Utilities -> Terminal</pre>
</section>
<p />
<p><b>Windows</b> (C:\windows\system32\cmd.exe)</p>
<section>
<pre>Start -> All Programs -> Accessories -> Command Prompt</pre>
</section>
</div>
</article>
<article id='ask-ruby'>
<style>
#ask-ruby .large-font { margin-top: 100px; }
</style>
<section class='build'>
<pre>irb</pre>
<pre>ruby-1.9.2-p290 :001 > </pre>
<p class='large-font'>Let's ask Ruby to do something.</p>
</section>
</article>
<article>
<section class='build'>
<pre>> 1 + 1</pre>
<pre>=> 2</pre>
<pre>> 462 * 86</pre>
<pre>=> 39732</pre>
<p class='large-font'>Ruby can do math, and it can do it much quicker than a person can.</p>
</section>
</article>
<article id='ruby-knows'>
<style>
#ruby-knows .large-font { margin-top: 100px; }
</style>
<section class='build'>
<pre>> 1 + 2 + 3<br>=> 6</pre>
<pre>> "ladies" + "learning" + "code"</pre>
<pre>=> "ladieslearningcode"</pre>
<p class='large-font'>Ruby knows the difference between a number and a word.</p>
</section>
</article>
<article id='integer-string'>
<style>
#integer-string .ruby-class { margin: 100px 0px; }
</style>
<h3>
Numbers and Words, Integers and Strings
</h3>
<p>In Ruby ...</p>
<p class='ruby-class'>Numbers without decimals are called <b>INTEGERS</b>. We just did some math with some integers.</p>
<p class='ruby-class'>Letters, words, and sentences are called <b>STRINGS</b>. We tell Ruby that we are intending to use a string by wrapping it in quotes.</p>
</article>
<article id='objects-objects'>
<style>
#objects-objects .large-font { margin: 150px 0px; }
</style>
<h3>
Objects, Objects, Everywhere!
</h3>
<p>You've already met Objects. That's a programming word!</p>
<div class='build'>
<p class='large-font'>Everything in Ruby is an Object.</p>
</div>
</article>
<article id='classes-galore'>
<style>
#classes-galore .build { margin-top: 40px; }
#classes-galore .large-font { margin: 70px 0px; }
</style>
<h3>Classes</h3>
<div class='build'>
<p>Ruby is extremely picky and needs to classify everything before it knows what to do with it.<br>Ruby knows that ...</p>
<p class='large-font'>The number <b>1</b> is an <b>Integer</b>.
<p class='large-font'>The word <b>"ladies"</b> is a <b>String</b>.
<p>Integers and Strings are classes in Ruby. That's another programming word!</p>
</div>
</article>
<article>
<h3>City</h3>
<div class='class-diagram'>
<img src="images/toronto.png">
<img src="images/london.jpg">
<br>
<img src="images/new-york.jpg">
<img src="images/paris.jpg">
</div>
</article>
<article id='city-instance'>
<style>
#city-instance p { margin: 70px 0px; }
</style>
<div class='build'>
<p class='large-font'>Toronto is an instance of the class City.</p>
<p class='large-font'>London is an instance of the class City.</p>
<p class='large-font'>New York is an instance of the class City.</p>
<p class='large-font'>Paris is an instance of the class City.</p>
</div>
</article>
<article id='string-class'>
<style>
#string-class div { padding: 20px; }
</style>
<h3>String</h3>
<div class='class-diagram'>
"ladies"<br><br>
"ladieslearningcode"<br><br>
"The dog jumped over the fence."
</div>
</article>
<article id='string-instance'>
<style>
#string-instance p { margin: 70px 0px; }
</style>
<div class='build'>
<p class='large-font'>"ladies" is an instance of the class String.</p>
<p class='large-font'>"ladieslearningcode" is an instance of the class String.</p>
<p class='large-font'>"The dog jumped over the fence." is an instance of the class String.</p>
</div>
</article>
<article>
<h3>
Playing with Integers
</h3>
<section class='build'>
<pre>> 99.next</pre>
<pre>=> 100</pre>
<pre>> 99.odd?</pre>
<pre>=> true</pre>
<pre>> 99.even?</pre>
<pre>=> false</pre>
</section>
</article>
<article>
<h3>
Simple String Manipulation
</h3>
<section class='build'>
<pre>> "ladieslearningcode".capitalize</pre>
<pre>=> "Ladieslearningcode"</pre>
<pre>> "ladieslearningcode".upcase</pre>
<pre>=> "LADIESLEARNINGCODE"</pre>
<pre>> "ladieslearningcode".reverse</pre>
<pre>=> "edocgninraelseidal"</pre>
</section>
</article>
<article id='ruby-method'>
<style>
#ruby-method .large-font { margin: 60px 0px; }
</style>
<h3>
Methods
</h3>
<div class='build'>
<p class='large-font'><b>next</b>, <b>odd?</b>, and <b>even?</b> are all methods that you can call on an Integer.</p>
<p class='large-font'><b>capitalize</b>, <b>upcase</b>, and <b>reverse</b> are all methods that you can call on a String.</p>
<p class='large-font'>Methods are actions.</p>
</div>
</article>
<article id='class-methods'>
<style>
#class-methods .large-font { margin: 200px 0px; }
</style>
<p class='large-font'>Classes come packaged with methods.</p>
</article>
<article>
<h3>
I'm lazy! I don't want to do all of this typing!
</h3>
<p>What if we could type in "ladieslearningcode" just once, and store it for later use? We can!</p>
<section>
<pre>> llc = "ladieslearningcode"</pre>
<pre>=> "ladieslearningcode"</pre></section>
<p>You've just <b>assigned</b> the String "ladieslearningcode to the <b>variable</b> llc.</p>
<p>A programmer would say that the variable llc points to the object "ladieslearningcode".</p>
</article>
<article>
<h3>
Variables Can (And Often Do!) Vary
</h3>
<p>A variable is called just that because the object it points to can change.</p>
<section class='build'>
<pre>> llc = "a lady learning code"</pre><pre>=> "a lady learning code"</pre>
<div>llc <img src='images/arrow.png'> "a lady learning code"</div>
<p>Now let's ask for the value of llc.</p>
<pre>> llc</pre><pre>=> "a lady learning code"</pre>
</section>
</article>
<article>
<p>Let's try some more</p>
<section class='build'>
<pre>> llc = 99</pre><pre>=> 99</pre>
<div>llc <img src='images/arrow.png'> 99</div>
<p>Let's ask for the value of llc once again.</p>
<pre>> llc</pre><pre>=> 99</pre>
</section>
</article>
<article>
<h3>The More the Merrier</h3>
<p>Let's introduce another variable.</p>
<section class='build'>
<pre>> copy_cat = llc</pre><pre>=> 99</pre>
<div>llc <img src='images/arrow.png'> 99 <img src='images/back-arrow.png'> copy_cat</div>
</section>
</article>
<article>
<p>Let's ask for the value of each variable.</p>
<section class='build'>
<pre>> llc</pre><pre>=> 99</pre>
<pre>> copy_cat</pre><pre>=> 99</pre>
<p>Now set llc back to "ladieslearningcode"</p>
<pre>> llc = "ladieslearningcode"</pre><pre>=> "ladieslearningcode"</pre>
</section>
</article>
<article>
<h3>
String Manipulation With Our Variable
</h3>
<p>You can now use this variable exactly like you would have used "ladieslearningcode" before.</p>
<section>
<pre>> llc.capitalize</pre>
<pre>=> "Ladieslearningcode"</pre>
<pre>> llc.upcase</pre>
<pre>=> "LADIESLEARNINGCODE"</pre>
<pre>> llc.reverse</pre>
<pre>=> "edocgninraelseidal"</pre>
</section>
</article>
<article>
<h3>Modifying the value with a method</h3>
<section class='build'>
<pre>> llc.reverse</pre><pre>=> "edocgninraelseidal"</pre>
<p>Try asking for the value of llc now.</p>
<pre>> llc</pre><pre>=> "ladieslearningcode"</pre>
</section>
</article>
<article id='wait-why'>
<style>
#wait-why p { margin: 50px 0px; }
</style>
<h3>Wait. Why didn't it change?</h3>
<section class='build'>
<p class='large-font'>llc is still pointing to "ladieslearningcode". You didn't tell it to point to a different string.</p>
<div>llc <img src='images/arrow.png'> "ladieslearningcode"</div>
<p class='large-font'>If you want the value to change, you have to set it to something else.</p>
</section>
</article>
<article>
<section class='build'>
<pre>> llc = llc.reverse</pre><pre>=> "edocgninraelseidal"</pre>
<pre>> llc</pre><pre>=> "edocgninraelseidal"</pre>
<p class='large-font'>If you want the value of a variable to change, you have to explicitly tell it to change.</p>
</section>
</article>
<article>
<h3>
Let's Try One More
</h3>
<div class='build'>
<pre>> llc.length</pre>
<pre>=> 18</pre>
<p class='large-font'>
You're probably starting to get a sense of how Twitter knows
how many characters you've typed in.
</p>
</div>
</article>
<article>
<h3>Doing like Twitter does.</h3>
<section class='build'>
<pre>> tweet = "I'm writing my first program at the @llcodedotcom<br>Intro to Ruby workshop!"</pre>
<pre>=> "I'm writing my first program at the @llcodedotcom <br>Intro to Ruby workshop!"</pre>
<pre>> tweet.length</pre>
<pre>=> 73</pre>
<p class='large-font'>We now know enough to write a program.</p>
</section>
</article>
<article>
<h3>
Writing Our First Program
</h3>
<p>
Open any text editor, add the same code, and save it as twitter.rb in your llc directory.
</p>
<section>
<pre>tweet = "I'm writing my first program at the @llcodedotcom<br>Intro to Ruby workshop!"<br>tweet.length</pre>
</section>
<p>To run your program, type <b>quit</b> to exit from IRB, and then type:</p>
<section>
<pre>ruby twitter.rb</pre>
</section>
<div class='build'><p>Wait, what? Why didn't it show me the length of my string?</p></div>
</article>
<article id='ruby-output'>
<style>
#ruby-output .large-font { margin: 50px 0px; }
</style>
<h3>
Outputting Text to the Screen
</h3>
<p class='large-font'>IRB is like back-and-forth text messaging.</p>
<p class='large-font'>A program has to be told when to output something</p>
<p>Modify your program:</p>
<section>
<pre>tweet = "I'm writing my first program at the @llcodedotcom<br>Intro to Ruby workshop!"<br>puts tweet.length</pre>
</section>
</article>
<!-- just words, highlight in a different colour before -->
<article id='recap-one'>
<style>
#recap-one .large-font { margin: 50px 0px; text-align: center; }
</style>
<h3>
Recap Slide
</h3>
<div class='build'>
<p class='large-font'>Integer</p>
<p class='large-font'>String</p>
<p class='large-font'>Class</p>
<p class='large-font'>Object</p>
<p class='large-font'>Variable</p>
</div>
</article>
<article id='puzzle-one'>
<style>
#puzzle-one .large-font { margin: 100px 0px; }
</style>
<h3>
Puzzle One - Variables
</h3>
<p class='large-font'>Open puzzle_1.rb in the puzzles folder, and write down the output you expect to see if you were to run this script.</p>
<p class='large-font'>If you're not sure of something, remember that you can type <b>irb</b> again and try it out.</p>
</article>
<article id='real-twitter'>
<style>
#real-twitter .large-font { margin: 60px 0px; }
</style>
<h3>
Getting Input From the User
</h3>
<p>The real Twitter...</p>
<div class='build'>
<p class='large-font'>Asks you to type something.</p>
<p class='large-font'>Tells you how many characters you're working with.</p>
<p>So far, we've just been putting our tweet directly into the program.</p>
</div>
</article>
<article>
<h3>
Asking for Input
</h3>
<p>The <b>puts</b> method is used for output, and the <b>gets</b> method is used for input. Try this:</p>
<p>The gets method warns Ruby that you're about to speak.</p>
<section class='build'>
<pre>> tweet = gets</pre>
<pre class='all-string'>I'm learning Ruby with #ladieslearningcode</pre><pre>=> "I'm learning Ruby with #ladieslearningcode\n"</pre>
<p>
Wait, we didn't type \n in our tweet. What is that?
</p>
</section>
</article>
<article>
<h3>
Asking for Input
</h3>
<p>
The \n is there because you hit the enter button after you typed your tweet. It represents a new line, and counts as exactly one character.
To get rid of it, do this:
</p>
<section class='build'>
<pre>> tweet = gets.chomp</pre>
<pre class='all-string'>I'm learning Ruby with #ladieslearningcode</pre>
<pre>=> "I'm learning Ruby with #ladieslearningcode"</pre>
</section>
</article>
<article>
<h3>
Asking for Input
</h3>
<p>Now try this:</p>
<section class='build'>
<pre>> tweet = gets.chomp</pre>
<pre class='all-string'>I'm a lady learning code with @llcodedotcom #ladieslearningcode</pre>
<pre>=> "I'm a lady learning code with @llcodedotcom #ladieslearningcode"</pre>
<pre>> puts tweet</pre>
<pre class='all-string'>I'm a lady learning code with @llcodedotcom #ladieslearningcode<br>=> nil</pre>
</section>
</article>
<article id='nil-nothing'>
<style>
#nil-nothing p { margin: 80px 0px; }
</style>
<h3>What's nil? It's nothing, don't worry.</h3>
<p>You asked Ruby to output your tweet, and Ruby did just that.</p>
<p>
Remember that in IRB, Ruby always responds to your message.
This time, it gave the output, and had nothing else to say, so it returned nil.
</p>
<p>nil is also an Object, and it just represents nothing.</p>
</article>
<article id='ask-for-tweet'>
<style>
#ask-for-tweet .build { margin-top: 60px; }
</style>
<h3>
Back to your Twitter Program
</h3>
<p>Working with your group, modify your Twitter program to do the following:</p>
<div class='build'>
<p>1. Ask (politely!) for a tweet from the user.</p>
<p>2. Store the tweet in a variable, without \n</p>
<p>3. Output the tweet the user gave.</p>
<p>4. Output the number of characters in the tweet.</p>
<p>5. Output how many <b>more</b> characters the user can add until they hit 140 characters.</p>
<p>(answers in assignments/twitter_3.rb)</p>
</div>
</article>
<article id='conditional-twitter-1'>
<style>
#conditional-twitter-1 .large-font { margin-top: 100px; }
</style>
<h3>
Giving Output Based on Input
</h3>
<p>Twitter...</p>
<p class='large-font'>Lets you send your tweet if it is 140 characters or less</p>
<p class='large-font'>Tells you that your tweet is too long to send otherwise.</p>
</article>
<article id='conditional-twitter-2'>
<style>
#conditional-twitter-2 .large-font { margin-top: 100px; }
</style>
<h3>Giving Output Based on Input</h3>
<p class='large-font'>
So far we know how to determine the length of the user's tweet.
</p>
<p class='large-font'>
We don't know how to tell them
whether they can or cannot send their tweet, depending on it's length.
</p>
</article>
<article id='conditional-logic'>
<style>
#conditional-logic .large-font { margin-top: 100px; }
</style>
<h3>Conditional Logic</h3>
<p class='large-font'>Programming is writing out sets of simple instructions for the computer to follow.</p>
<p class='large-font'>Let's break down out tweet logic into simple instructions.</p>
</article>
<article id='conditional-instructions'>
<style>
#conditional-instructions .large-font { margin-top: 80px; }
</style>
<h3>
Conditional Logic
</h3>
<p>We want our program to ...</p>
<p class='large-font'>if the tweet is greater than 140 characters, tell the user that they cannot send their tweet</p>
<p class='large-font'>if the tweet is less than or equal to 140 characters, tell the user that they can send their tweet</p>
</article>
<article id='greater-than'>
<style>
#greater-than .large-font { margin: 100px 0px; }
</style>
<h3>
Conditional Logic: Greater Than
</h3>
<p class='large-font'>The math symbol for <b>greater than</b> is <b>></b></p>
<p>Try the code below in IRB:</p>
<section class='build'>
<pre>> 200 > 140</pre><pre>=> true</pre>
</section>
</article>
<article>
<h3>
Conditional Logic: Greater Than
</h3>
<p>Now try:</p>
<section class='build'>
<pre>> number_of_characters = 200</pre><pre>=> 200</pre>
<pre>> number_of_characters > 140</pre><pre>=> true</pre>
</section>
</article>
<article>
<h3>
Conditional Logic: Greater Than
</h3>
<p>Now try:</p>
<section class='build'>
<pre>> number_of_characters = 80</pre><pre>=> 80</pre>
<pre>> number_of_characters > 140</pre><pre>=> false</pre>
</section>
</article>
<article id='less-than'>
<style>
#less-than .large-font { margin: 50px 0px; }
</style>
<h3>
Conditional Logic: Less Than
</h3>
<p class='large-font'>The math symbol for <b>less than</b> is <b><</b></p>
<p>Try the code below in irb</p>
<section class='build'>
<pre>> llc = "ladieslearningcode"</pre><pre>=> "ladieslearningcode"</pre>
<pre>> llc.length < 140</pre><pre>=> true</pre>
</section>
</article>
<article id='conditional-logic'>
<h3>
Conditional Logic in Our Simple Twitter
</h3>
<p class='large-font'>Let's simplify our if statements.</p>
<p class='large-font'>Remember that we're storing the user's tweet in the variable tweet.</p>
</article>
<article id='conditional-simplify'>
<style>
#conditional-simplify p { margin: 50px 0px; }
</style>
<h3>
Conditional Logic in Our Simple Twitter
</h3>
<p>Original if statements:</p>
<p>if the tweet is greater than 140 characters, tell the user that they cannot send their tweet</p>
<p>if the tweet is less than 140 characters, tell the user that they can send their tweet</p>
<p />
<div class='build'>
<!-- split up, and put actual statement instead of crap code -->
<p>if tweet.length > 140 puts "Your tweet is too long!"</p>
<p>if tweet.length < 140 puts "Tweet your heart out!"</p>
</div>
</article>
<article>
<h3>
Try it out!
</h3>
<p>
Replace the puts statements in your Twitter program with the code below.
(see assignments/twitter_4.rb if needed)
</p>
<section>
<pre>if tweet.length > 140<br> puts "Your tweet is too long!"<br>end<br><br>if tweet.length < 140<br> puts "Tweet your heart out!"<br>end</pre>
</section>
<p>
Using the tweets from tweets.txt, try out your new script!
What's the problem here? What do you notice happened when using the tweets in tweets.txt?
</p>
</article>
<article id='conditional-instructions'>
<h3>
Your First Bug!
</h3>
<p class='large-font'>We're not actually taking into account all possible tweet lengths.</p>
<p class='large-font'>Programming problems can be solved many different ways.</p>
<p class='large-font'>We'll look at three different solutions.</p>
</article>
<article id='conditional-logic'>
<h3>
First (Worst) Solution
</h3>
<p class='large-font'>Since we're only missing one case, the case where the tweet is exactly 140 characters, we can just add another if statement.</p>
</article>
<article>
<h3>
First (Worst) Solution
</h3>
<p>Add this last if statement to the bottom of your file: (see assignments/twitter_5.rb if needed)</p>
<section>
<pre>if tweet.length == 140<br> puts "Tweet your heart out!"<br>end</pre>
</section>
<p class='large-font'>
The == operator checks that the value of the objects on either side of it are equal.
</p>
</article>
<article id='conditional-logic'>
<h3>
Refactoring Our Code
</h3>
<p class='large-font'>
Programmers are always refactoring (re-strcturing, re-organizing) their code to make it cleaner and more readable.
Right now is a great time to do that.
</p>
</article>
<article>
<h3>
Refactoring Our Code
</h3>
<p>Three if statements are unnecessary. We can actually combine all of these if statements into one, like so:</p>
<section>
<pre>if tweet.length > 140<br> puts "Your tweet is too long!"<br>elsif tweet.length < 140<br> puts "Tweet your heart out!"<br>elsif tweet.length == 140<br> puts "Tweet your heart out!"<br>end</pre>
</section>
<p>(see assignments/twitter_6.rb if needed)</p>
</article>
<article id='conditional-logic'>
<h3>if .. elsif</h3>
<section>
<pre>if tweet.length > 140<br> puts "Your tweet is too long!"<br>elsif tweet.length < 140<br> puts "Tweet your heart out!"<br>elsif tweet.length == 140<br> puts "Tweet your heart out!"<br>end</pre>
</section>
<p class='large-font'>In the above code, if the first statement doesn't evaluate to true, then the next one is attempted, and so on.</p>
</article>
<article id='conditional-logic'>
<h3>if .. elsif</h3>
<section>
<pre>if tweet.length > 140<br> puts "Your tweet is too long!"<br>elsif tweet.length < 140<br> puts "Tweet your heart out!"<br>elsif tweet.length == 140<br> puts "Tweet your heart out!"<br>end</pre>
</section>
<p class='large-font'>
Only one puts statement is ever executed.
The statements are evaluated in the order they are written, so the first one to evaluate to true is the only one executed.
</p>
</article>
<article id='conditional-logic'>
<h3>if .. elsif</h3>
<section>
<pre>if tweet.length > 140<br> puts "Your tweet is too long!"<br>elsif tweet.length < 140<br> puts "Tweet your heart out!"<br>elsif tweet.length == 140<br> puts "Tweet your heart out!"<br>end</pre>
</section>
<p class='large-font'>If none of the statements evaluate to true, then none of the puts statements are executed.</p>
</article>
<article>
<h3>
Second Solution
</h3>
<p>Notice that the line puts "Tweet your hear out!" is unnecessarily repeated?</p>
<p>Let's cut it out by replacing the entire if statement with the code below:</p>
<section>
<pre>if tweet.length > 140<br> puts "Your tweet is too long!"<br>elsif tweet.length <= 140<br> puts "Tweet your heart out!"<br>end</pre>
</section>
<p>(see assignments/twitter_7.rb if needed)</p>
</article>
<article id='conditional-instructions'>
<h3>Less than or equal to with <=, Greater than or equal to with >=</h3>
<p class='large-font'>The <b><=</b> operator checks for equality as well.</p>
<p class='large-font'>Checking for equality with greater than works exactly the same way, using the <b>>=</b> operator.</p>
</article>
<article>
<h3>
Third Time's a Charm
</h3>
<p>
This is better, but look at the logic closely. Do we really even need to specify the second condition?
</p>
<p>Replace your code again with the code below:</p>
<section>
<pre>if tweet.length > 140<br> puts "Your tweet is too long!"<br>else<br> puts "Tweet your heart out!"<br>end</pre>
</section>
<p>(see assignments/twitter_8.rb if needed)</p>
</article>
<article id='conditional-logic'>
<h3>if .. else</h3>
<section>
<pre>if tweet.length > 140<br> puts "Your tweet is too long!"<br>else<br> puts "Tweet your heart out!"<br>end</pre>
</section>
<p class='large-font'>
Just like with if .. elsif, only one puts statement is ever executed. The difference here is that one of the
puts statements is <b>always</b> executed.
</p>
</article>
<article id='conditional-logic'>
<h3>if .. else</h3>
<section>
<pre>if tweet.length > 140<br> puts "Your tweet is too long!"<br>else<br> puts "Tweet your heart out!"<br>end</pre>
</section>
<p class='large-font'>
The else is there are a <b>catch-all</b>. You can think of it like a last resort.
If none of the other options are true, then just execute the puts statement after the else.
</p>
</article>
<article>
<h3>Hello, Operator?</h3>
<table>
<tr><td>Operator</td><td>True</td><td>False</td></tr>
<tr>
<td>==</td>
<td>99 == 99</td>
<td>99 == 100</td>
</tr>
<tr>
<td>!=</td>
<td>99 != 100</td>
<td>99 != 99</td>
</tr>
<tr>
<td>></td>
<td>100 > 99</td>
<td>99 > 100</td>
</tr>
<tr>
<td><</td>
<td>99 < 100</td>
<td>100 < 99</td>
</tr>
<tr>
<td>>=</td>
<td>99 >= 99</td>
<td>99 >= 100</td>
</tr>
<tr>
<td><=</td>
<td>99 <= 99</td>
<td>100 <= 99</td>
</tr>
</table>
</article>
<article id='recap-two'>
<h3>Recap Slide</h3>
<style>
#recap-two .large-font { margin: 50px 0px; text-align: center; }