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annotate 2-Io/day1-self-study.io @ 36:15eb99e79dd4

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Call methods by name and fix slot name printing
author IBBoard <dev@ibboard.co.uk>
date Tue, 12 Sep 2017 20:07:04 +0100
parents 22edfbf3b8bd
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1 #Truthiness:
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2 # We already know that 0 is truthy
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3 (true and 0) println
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4 # Empty strings are apparently truthy
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5 (true and "") println
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6 # As are empty lists
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7 (true and list()) println
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8 # But nil is falsey
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9 (true and nil) println
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10 # So basically anything except `false` and `nil` is truthy
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12 # = vs := vs ::=
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13 # Obvious part so far is that you must create with := before being able to assign with plain =
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14 myvar := Object clone
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15 myvar println
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16 myvar = Object clone
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17 # Docs say:
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18 # ::= Creates slot, creates setter, assigns value
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19 # := Creates slot, assigns value
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20 # = Assigns value to slot if it exists, otherwise raises exception
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21 # But what is a "setter" in this context?
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22 myvar foo ::= Object clone
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23 myvar println
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24 # It seems we get a "setX" method, which helps us do some things in certain contexts:
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25 # https://stackoverflow.com/a/5977757
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27 # What slots does a prototype support? Direct ones are human readable in the output
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28 myvar proto println
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29 # But they're not listed indirectly
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30 SubClass := Object clone
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31 myvar2 := SubClass clone
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32 myvar2 proto println
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33 # Can we find it out programattically?
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34 # It's not recursive, but the type should tell us:
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35 myvar2 type proto println
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36 # Except the value of `type` is just a string (or Sequence in Io), so it doesn't
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37 myvar2 type proto type println
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38 # Or, of course, a Prototype is a named object that starts with a capital letter
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39 # So we can just use slotNames to get them programmatically (but that only shows direct slots)
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40 myvar slotNames println
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41 # And to get the parent ones then we just chain "proto"
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42 myvar proto slotNames println
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43 myvar proto proto slotNames println
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44 # If I knew enough Io then I'd do a recursion loop and walk up until proto == Object
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48 #Execute methods by slot name - use "perform"
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49 SubClass method1 := method("Method 1 was called" println)
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50 SubClass method2 := method("Method 2 was called" println)
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51 myvar2 perform("method1")
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52 myvar2 perform("method2")
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56 # Is Io strongly or weakly typed?
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57 (1 + 1) println
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58 (1 + "one") println
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59 # Exception: argument 0 to method '+' must be a Number, not a 'Sequence'
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60 # Therefore strongly typed