Data commit

Task/Array-length/AppleScript/array-length-1.applescript

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+set theList to {"apple", "orange"}
+count theList
+-- or
+length of theList
+-- or
+number of items in theList

Task/Array-length/AppleScript/array-length-2.applescript

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+on run
+
+    set xs to ["alpha", "beta", "gamma", "delta", "epsilon", ¬
+        "zeta", "eta", "theta", "iota", "kappa", "lambda", "mu"]
+
+    {_length(xs), fold(xs, succ, 0), item 12 of xs, item -1 of xs}
+
+    --> {12, 12, "mu", "mu"}
+
+end run
+
+-- TWO FUNCTIONAL DEFINITIONS OF LENGTH
+
+-- 1. Recursive definition
+
+on _length(xs)
+    if xs is [] then
+        0
+    else
+        1 + _length(rest of xs)
+    end if
+end _length
+
+
+-- 2. fold (λx n -> 1 + n)  0
+
+on succ(x)
+    1 + x
+end succ
+
+--[a] - > (a - > b) - > b - > [b]
+on fold(xs, f, startValue)
+    script mf
+        property lambda : f
+    end script
+
+    set v to startValue
+    repeat with x in xs
+        set v to mf's lambda(v, x)
+    end repeat
+end fold