answers.io

##################################
## DAY 1

# Evaluate 1 + 1 and then 1 + "one". Is Io strongly typed or weakly typed? 
1 + 1
1+"one" 
# > Exception: argument 0 to method '+' must be a Number, not a 'Sequence'

# Io is Strong: it does not perform implicit casts between types. 

############################################################


# Is 0 true or false? 
0 and true
# ==> true

0 or false
# ==> true

0 == true
# ==> false

# .: 0 is equivalent to `true` without being identical.


# What about the empty string? 
"" and true
# ==> true

"" or true
# ==> true

"" == true
# ==> false

# Same story


# Is nil true or false? 
nil and true
# ==> false

nil or false
# ==> false

nil == true
# ==> false

# So `nil` is not true in any sense.

############################################################

# How can you tell what slots a prototype supports?
Object slotNames

# ==> list(or, coroDo, ifError, handleActorException, do, inlineMethod, -, isIdenticalTo, slotNames, become, actorProcessQueue, removeProto, asBoolean, markClean, contextWithSlot, argIsActivationRecord, deprecatedWarning, removeAllSlots, launchFile, super, yield, setProtos, evalArgAndReturnSelf, returnIfError, print, ownsSlots, continue, asyncSend, evalArgAndReturnNil, removeAllProtos, in, doString, compare, serialized, isKindOf, <=, setSlot, cloneWithoutInit, serializedSlots, isError, protos, returnIfNonNil, resend, thisContext, coroFor, evalArg, switch, memorySize, isLaunchScript, hasLocalSlot, @, thisMessage, raiseIfError, ancestorWithSlot, while, type, block, , hasSlot, performWithArgList, pause, ifNil, clone, try, asSimpleString, ==, writeln, not, relativeDoFile, .., ifNonNil, getSlot, slotSummary, uniqueHexId, <, init, shallowCopy, wait, justSerialized, proto, lexicalDo, foreachSlot, uniqueId, slotDescriptionMap, for, return, coroWith, argIsCall, serializedSlotsWithNames, >, perform, >=, doRelativeFile, setSlotWithType, stopStatus, ancestors, @@, println, break, appendProto, isNil, asString, ifNilEval, getLocalSlot, isActivatable, hasProto, doMessage, if, slotValues, coroDoLater, list, futureSend, lazySlot, message, currentCoro, and, write, method, setIsActivatable, !=, ?, apropos, loop, thisLocalContext, addTrait, setProto, ifNonNilEval, updateSlot, actorRun, isTrue, removeSlot, newSlot, hasDirtySlot, doFile, prependProto)

# ; This language is not THAT simple.
###############################################################################


# What is the difference between = (equals), := (colon equals), and ::= (colon colon equals)? 

# := creates slot and assigns a value
a := 1
# == newSlot("a", 1)


# = assigns a value in a slot that already exists
a = 2
b = 3
# == updateSlot("a", 2)

# ::= creates a slot, a setter, and assigns a value
b ::= 1
setB(3)


######################################################
# Run an Io program from a file.
# io f.io

######################################################
# Execute the code in a slot given its name.

Detective := Object clone do(
  deduce := method("aha!" print)
)
holmes := Detective clone
givenItsName := "deduce"
holmes getSlot(givenItsName) call


##################################
## DAY 2

# Write a program to find the nth Fibonacci number. solve the problem with recursion 

fib := method(n,
  if (n < 1, Exception raise(n .." is not a valid index!"))
  if (n < 3, return 1)
  else ( return (fib(n-1) + fib(n-2) )
)

# and with loops. 

loop := method(n, 
               first := second := 1;               
               for( 0, 1, n-1,
                    acc := first + second;
                    first = second;
                    second = acc;
               )
               (return first)
)


# How would you change / to return 0 if the denominator is zero?

realDiv := Number getSlot("/")
Number / = method( divisor, if (divisor == 0, 0, realDiv(divisor)) )


# Write a program to add up all of the numbers in a two-dimensional array. 
matrix := list(list(1, 1, 2), list(3, 5, 8), list(13, 21, 34))
sum2d := method(m, m flatten sum)


# Add a slot called myAverage to a list that computes the average of all the numbers in a list. What happens if there are no numbers in a list? (Bonus: Raise an Io exception if any item in the list is not a number.)

List myAverage := method( if (size > 0, 
                          (return sum / size), 
                          Exception raise("Can't avg emptiness") ) 
                        )

list(55, 89, 144) myAverage
list(55, 89, "a") myAverage   # already throws an exception
list() myAverage


# Write a prototype for a two-dimensional list. 
# The dim(x, y) method should allocate a list of y lists that are x elements long. 
# set(x, y, value) should set a value, 
# get(x, y) should return that value.
# Write the matrix to a file

List2d := List clone do(
  (dim := method(x, y,
        self setSize(x); 
        for (i, 0, (x - 1), 1,
            self atPut( i, (list setSize(y)) )
        )
  ))
  
  (get := method (x, y,
        return self at(x) at(y)
  ))
  
  (set := method (x, y, value,
              self at(x) atPut(y, value);
              return self
  ))
  
  (save := method (file,
            File with(file) open write(self serialized) close
  ))
)

2d := List2d clone dim(3,4)
for( i, 0, 2, 
    2d set(i, i, i)
)
2d save("mat.dat")


##########################################################
# Write a program that gives you ten tries to guess a random number from 1--100. 

rand := (Random value(100) floor) + 1
reader := File standardInput

i := 0
while( i < 10,
      guess := reader readLine("Guess: ") asNumber;
      if (guess isNan, Exception raise("NaN!"));
      if( rand == guess,
              "Ye that's the one" println;
              break
      );
      i := i + 1;
)

##################################
## DAY 3

# Enhance the XML program to add spaces to show the indentation structure.

Builder := Object clone do(
  (depth ::= 0)
  (indent := "    ")
  (spaces := method( indent repeated(depth) ))
  
  (print_spaced := method( arg,
        content := doMessage( arg );
        if ( content != nil, writeln(spaces, content) );
  ))
  
  (shift_depth := method(offs, setDepth( depth + offs )))
  
  (tag := method(name, closer, writeln(spaces, "<", closer, name, ">") ))
  
  (forward := method(
        reflection := call message() name();
        tag(reflection, "");
        shift_depth(1);
        call message() arguments() foreach( arg, 
            print_spaced(arg) 
        );
        shift_depth(-1);
        tag(reflection, "/");
  ))
)

Builder ul( li("Io"), li("Lua"), li(div("fuck io"), "Javascript"), li("Lisp") )


##########################################
# Create a list syntax that uses brackets. 

# Assume he means curlies. Another methodMissing trick: vals are args passed to curlyBrackets.
# Convert args to vals, then map them to a List:

curlyBrackets := method(
    call message arguments map( arg, doMessage(arg) );
);

{ "a", "b", "c" }