Intro
This is a group for puzzles, hints and solutions (but hidden, without spoilers).
A certain enchanted forest is inhabited by talking birds. Given any birds A and B, if you call out the name of B to A, then A will respond by calling out the name of some bird to you; this bird we designate AB. Thus AB is the bird named by A upon hearing the name of B.
C1: Composition: Given any birds A, B & C the bird C is said to compose A with B if for every bird x the following condition holds:
A(Bx) = Cx
C2: Mockingbird: a bird M such that for any bird x, the following condition holds:
Mx = xx
M is called a mockingbird for the simple reason that its response to any bird x is the same as x's response to itself -- in other words, M mimics x as far as its response to x goes.
A certain enchanted forest is inhabited by talking birds. Given any birds A and B, if you call out the name of B to A, then A will respond by calling out the name of some bird to you; this bird we designate AB. Thus AB is the bird named by A upon hearing the name of B.
C1: Composition: Given any birds A, B & C the bird C is said to compose A with B if for every bird x the following condition holds:
A(Bx) = Cx
C2: Mockingbird: a bird M such that for any bird x, the following condition holds:
Mx = xx
M is called a mockingbird for the simple reason that its response to any bird x is the same as x's response to itself -- in other words, M mimics x as far as its response to x goes.