{
 "cells": [
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "Exercises from *A Book of Abstract Algebra* by *Charles C Pinter* solved in Raku.\n",
    "\n",
    "# 5.F. Groups Determined by Generators and Defining Equations"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Helper function `zip-many`"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "sub zip-many (@arrs) { #`(Sub|139734349541608) ... }"
      ]
     },
     "execution_count": 1,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "sub zip-many (@arrs) { @arrs == 1 ?? @arrs[0][] !! [Z] @arrs }"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# The heart of the program: `generate`"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "sub generate (%eqs, $s) { #`(Sub|139734349547384) ... }"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "sub generate(%eqs, $s)\n",
    "{\n",
    "    my @results;\n",
    "\n",
    "    for %eqs.kv -> $key, $val {\n",
    "        if $s ~~ /$key/ { @results.push($s.subst(/$key/, $val)); }\n",
    "        if $s ~~ /$val/ { @results.push($s.subst(/$val/, $key)); }\n",
    "    }\n",
    "\n",
    "    .take for @results;\n",
    "\n",
    "    .take for flat zip-many @results.map({ gather generate(%eqs, $_) });\n",
    "}"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Subroutine to display the table"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "sub table (@G, %eqs) { #`(Sub|139734349553312) ... }"
      ]
     },
     "execution_count": 3,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "sub table(@G, %eqs)\n",
    "{\n",
    "    printf \"     |\";   for @G -> $y { printf \"%-5s|\", $y; }; say '';\n",
    "\n",
    "    printf \"-----|\";   for @G -> $y { printf \"-----|\";    }; say '';\n",
    "\n",
    "    for @G -> $x {\n",
    "\n",
    "        printf \"%-5s|\", $x;\n",
    "\n",
    "        for @G -> $y {\n",
    "            my $result = (gather generate(%eqs, \"$x$y\")).first(* ∈ @G);\n",
    "\n",
    "            printf \"%-5s|\", $result;\n",
    "        }\n",
    "    say ''\n",
    "    }    \n",
    "}"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "# Exercises"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "** 5.G.1 **\n",
    "\n",
    "Let $G$ be the group:\n",
    "\n",
    "\\begin{align*}\n",
    "\\{e,a,b, b^2, ab, ab^2\\}\n",
    "\\end{align*}\n",
    "\n",
    "whose generators satisfy: \n",
    "\n",
    "\\begin{align*}\n",
    "a^2 & = e \\\\\n",
    "b^3 & = e \\\\\n",
    "ba  & = ab^2\n",
    "\\end{align*}\n",
    "\n",
    "Write the table of $G$."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "     |e    |a    |b    |bb   |ab   |abb  |\n",
      "-----|-----|-----|-----|-----|-----|-----|\n",
      "e    |e    |a    |b    |bb   |ab   |abb  |\n",
      "a    |a    |e    |ab   |abb  |b    |bb   |\n",
      "b    |b    |abb  |bb   |e    |a    |ab   |\n",
      "bb   |bb   |ab   |e    |b    |abb  |a    |\n",
      "ab   |ab   |bb   |abb  |a    |e    |b    |\n",
      "abb  |abb  |b    |a    |ab   |bb   |e    |\n"
     ]
    }
   ],
   "source": [
    "my @G = <e a b bb ab abb>;\n",
    "\n",
    "my %eqs = <aa e   bbb e   ba abb>; %eqs<e> = '';\n",
    "\n",
    "table @G, %eqs;"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**5.G.2**\n",
    "\n",
    "Let $G$ be the group\n",
    "\n",
    "\\begin{align*}\n",
    "\\{ e, a, b, b^2, b^3, ab, ab^2, ab^3 \\}\n",
    "\\end{align*}\n",
    "\n",
    "whose generators satisfy\n",
    "\n",
    "\\begin{align*}\n",
    "a^2 & = e    \\\\\n",
    "b^4 & = e    \\\\\n",
    "ba  & = ab^3\n",
    "\\end{align*}\n",
    "\n",
    "Write the table of $G$."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "     |e    |a    |b    |bb   |bbb  |ab   |abb  |abbb |\n",
      "-----|-----|-----|-----|-----|-----|-----|-----|-----|\n",
      "e    |e    |a    |b    |bb   |bbb  |ab   |abb  |abbb |\n",
      "a    |a    |e    |ab   |abb  |abbb |b    |bb   |bbb  |\n",
      "b    |b    |abbb |bb   |bbb  |e    |a    |ab   |abb  |\n",
      "bb   |bb   |abb  |bbb  |e    |b    |abbb |a    |ab   |\n",
      "bbb  |bbb  |ab   |e    |b    |bb   |abb  |abbb |a    |\n",
      "ab   |ab   |bbb  |abb  |abbb |a    |e    |b    |bb   |\n",
      "abb  |abb  |bb   |abbb |a    |ab   |bbb  |e    |b    |\n",
      "abbb |abbb |b    |a    |ab   |abb  |bb   |bbb  |e    |\n"
     ]
    }
   ],
   "source": [
    "my @G = <e a b bb bbb ab abb abbb>;\n",
    "\n",
    "my %eqs = <aa e   bbbb e   ba abbb>; %eqs<e> = '';\n",
    "\n",
    "table @G, %eqs;"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "**5.G.3**\n",
    "\n",
    "Let $G$ be the group\n",
    "\n",
    "\\begin{align*}\n",
    "\\{ e, a, b, b^2, b^3, ab, ab^2, ab^3 \\}\n",
    "\\end{align*}\n",
    "\n",
    "whose generators satisfy\n",
    "\n",
    "\\begin{align*}\n",
    "a^4 & = e    \\\\\n",
    "a^2 & = b^2  \\\\\n",
    "ba  & = ab^3\n",
    "\\end{align*}\n",
    "\n",
    "Write the table of $G$."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "     |e    |a    |b    |bb   |bbb  |ab   |abb  |abbb |\n",
      "-----|-----|-----|-----|-----|-----|-----|-----|-----|\n",
      "e    |e    |a    |b    |bb   |bbb  |ab   |abb  |abbb |\n",
      "a    |a    |bb   |ab   |abb  |abbb |bbb  |e    |b    |\n",
      "b    |b    |abbb |bb   |bbb  |e    |a    |ab   |abb  |\n",
      "bb   |bb   |abb  |bbb  |e    |b    |abbb |a    |ab   |\n",
      "bbb  |bbb  |ab   |e    |b    |bb   |abb  |abbb |a    |\n",
      "ab   |ab   |b    |abb  |abbb |a    |bb   |bbb  |e    |\n",
      "abb  |abb  |e    |abbb |a    |ab   |b    |bb   |bbb  |\n",
      "abbb |abbb |bbb  |a    |ab   |abb  |e    |b    |bb   |\n"
     ]
    }
   ],
   "source": [
    "my @G = <e a b bb bbb ab abb abbb>;\n",
    "\n",
    "my %eqs = <aaaa e   aa bb   ba abbb>; %eqs<e> = '';\n",
    "\n",
    "table @G, %eqs;"
   ]
  }
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