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<li class="header">LEARN LISP THE HARD WAY</li>
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Second Draft (in-progress)
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CHANGELOG
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TODO
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<li class="header">PREFACE</li>
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TANSTAAFL
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The Hard Way is Easier
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Who Is This Book For?
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Lisp: A Future History
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Acknowledgements
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<li class="header">PART ONE</li>
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Grokking Lisp
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Common Lisp Bootcamp
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Syntax Overview in 5 Minutes
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<li class="chapter " data-level="3.1.1.2" data-path="1-01-02-repl.html">
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The REPL
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Expressions, Parentheses, and Return Values
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Lists, Cons-Cells, and Memory
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Symbols and Namespaces
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Prefix Notation
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Common Lisp Style Guide
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Configuring Your Development Environment
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Printing, Streams, and Strings
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Strings
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More Strings
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Unicode and Strings
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Characters
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<li class="chapter " data-level="3.1.2.5" data-path="1-02-05-more-chars.html">
<a href="1-02-05-more-chars.html">
More Characters
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<li class="chapter " data-level="3.1.2.6" data-path="1-02-06-char-codes.html">
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Character Codes
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<li class="chapter " data-level="3.1.2.7" data-path="1-02-07-strings-from-chars.html">
<a href="1-02-07-strings-from-chars.html">
Strings from Chars
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<li class="chapter " data-level="3.1.2.8" data-path="1-02-08-printing.html">
<a href="1-02-08-printing.html">
Printing
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<li class="chapter " data-level="3.1.2.9" data-path="1-02-09-more-printing.html">
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More Printing
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<li class="chapter " data-level="3.1.2.10" data-path="1-02-10-prin1.html">
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Printing With prin1
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<li class="chapter " data-level="3.1.2.11" data-path="1-02-11-princ.html">
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Printing With princ
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<li class="chapter " data-level="3.1.2.12" data-path="1-02-12-format.html">
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A Brief Introduction to Format
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<li class="chapter " data-level="3.1.2.13" data-path="1-02-13-more-format.html">
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A Little Bit More on Format
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<li class="chapter " data-level="3.1.2.14" data-path="1-02-14-pathnames.html">
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Pathnames
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<li class="chapter " data-level="3.1.2.15" data-path="1-02-15-streams.html">
<a href="1-02-15-streams.html">
Streams
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<li class="chapter " data-level="3.1.2.16" data-path="1-02-16-file-streams.html">
<a href="1-02-16-file-streams.html">
File Streams
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<li class="chapter " data-level="3.1.2.17" data-path="1-02-17-binary-streams.html">
<a href="1-02-17-binary-streams.html">
Binary Streams
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<li class="chapter " data-level="3.1.2.18" data-path="1-02-18-prompting-users.html">
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Prompting Users
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<li class="chapter " data-level="3.1.2.19" data-path="1-02-19-pretty-printing.html">
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Pretty-Printing
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<li class="chapter " data-level="3.1.3" data-path="1-03-0-getting-input-from-users.html">
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Extra Credit: Getting Input from Users
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<li class="chapter " data-level="3.1.4" data-path="1-04-0-lists.html">
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Lists and List-Operations
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Extra Credit: Look-up Lists and Trees
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<li class="chapter " data-level="3.1.6" data-path="1-06-0-math.html">
<a href="1-06-0-math.html">
Numbers and Math
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Integers
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<li class="chapter " data-level="3.1.6.2" data-path="1-06-02-more-integers.html">
<a href="1-06-02-more-integers.html">
More Integers
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<li class="chapter " data-level="3.1.6.3" data-path="1-06-03-hexadecimal-notation.html">
<a href="1-06-03-hexadecimal-notation.html">
Hexadecimal Integer Notation
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</li>
<li class="chapter " data-level="3.1.6.4" data-path="1-06-04-octal-notation.html">
<a href="1-06-04-octal-notation.html">
Octal Integer Notation
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</li>
<li class="chapter " data-level="3.1.6.5" data-path="1-06-05-binary-notation.html">
<a href="1-06-05-binary-notation.html">
Binary Integer Notation
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<li class="chapter " data-level="3.1.6.6" data-path="1-06-06-ratios.html">
<a href="1-06-06-ratios.html">
Ratios and Rational Numbers
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</li>
<li class="chapter " data-level="3.1.6.7" data-path="1-06-07-floating-point.html">
<a href="1-06-07-floating-point.html">
Floating-point Numbers
</a>
</li>
<li class="chapter " data-level="3.1.6.8" data-path="1-06-08-constants.html">
<a href="1-06-08-constants.html">
Numeric Constants
</a>
</li>
<li class="chapter " data-level="3.1.6.9" data-path="1-06-09-complex-numbers.html">
<a href="1-06-09-complex-numbers.html">
Complex Numbers
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<li class="chapter " data-level="3.1.6.10" data-path="1-06-10-arithmetic.html">
<a href="1-06-10-arithmetic.html">
Arithmetic
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<li class="chapter " data-level="3.1.6.11" data-path="1-06-11-more-arithmetic.html">
<a href="1-06-11-more-arithmetic.html">
More Arithmetic
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<li class="chapter " data-level="3.1.6.12" data-path="1-06-12-even-more-arithmetic.html">
<a href="1-06-12-even-more-arithmetic.html">
Even More Arithmetic
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<li class="chapter " data-level="3.1.6.13" data-path="1-06-13-exponents.html">
<a href="1-06-13-exponents.html">
Exponents
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<li class="chapter " data-level="3.1.6.14" data-path="1-06-14-logarithms.html">
<a href="1-06-14-logarithms.html">
Logarithms
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</li>
<li class="chapter " data-level="3.1.6.15" data-path="1-06-15-trigonometry.html">
<a href="1-06-15-trigonometry.html">
Trigonometry
</a>
</li>
<li class="chapter " data-level="3.1.6.16" data-path="1-06-16-psuedorandom-numbers.html">
<a href="1-06-16-psuedorandom-numbers.html">
Pseudo-Random Numbers
</a>
</li>
</ul>
</li>
<li class="chapter " data-level="3.1.7" data-path="1-07-0-arrays.html">
<a href="1-07-0-arrays.html">
Extra Credit: Arrays and Vectors
</a>
</li>
<li class="chapter " data-level="3.1.8" data-path="1-08-0-variables.html">
<a href="1-08-0-variables.html">
Variables, Parameters, and Constants
</a>
</li>
<li class="chapter " data-level="3.1.9" data-path="1-09-0-closures.html">
<a href="1-09-0-closures.html">
Extra Credit: Closures
</a>
</li>
<li class="chapter " data-level="3.1.10" data-path="1-10-0-functions.html">
<a href="1-10-0-functions.html">
Functions and Macros
</a>
</li>
<li class="chapter " data-level="3.1.11" data-path="1-11-0-text-adventure.html">
<a href="1-11-0-text-adventure.html">
Extra Credit: A Simple Text Adventure
</a>
</li>
<li class="chapter " data-level="3.1.12" data-path="1-12-0-namespaces.html">
<a href="1-12-0-namespaces.html">
Namespaces, Symbols, Packages, and Systems
</a>
</li>
<li class="chapter " data-level="3.1.13" data-path="1-13-0-simple-web-app.html">
<a href="1-13-0-simple-web-app.html">
Extra Credit: A Simple Web Application
</a>
</li>
<li class="chapter " data-level="3.1.14" data-path="1-14-0-conditionals.html">
<a href="1-14-0-conditionals.html">
Conditionals
</a>
</li>
<li class="chapter " data-level="3.1.15" data-path="1-15-0-command-line-utility.html">
<a href="1-15-0-command-line-utility.html">
Extra Credit: Command-Line Utilities
</a>
</li>
<li class="chapter active" data-level="3.1.16" data-path="1-16-0-map-loop.html">
<a href="1-16-0-map-loop.html">
Mapping and Looping
</a>
</li>
<li class="chapter " data-level="3.1.17" data-path="1-17-0-iterate.html">
<a href="1-17-0-iterate.html">
Extra Credit: Revisiting Loops with Iterate
</a>
</li>
<li class="chapter " data-level="3.1.18" data-path="1-18-0-format.html">
<a href="1-18-0-format.html">
Format Strings
</a>
</li>
<li class="chapter " data-level="3.1.19" data-path="1-19-0-dsl.html">
<a href="1-19-0-dsl.html">
Extra Credit: Domain Specific Languages
</a>
</li>
<li class="chapter " data-level="3.1.20" data-path="1-20-0-review.html">
<a href="1-20-0-review.html">
Part One in Review
</a>
</li>
</ul>
</li>
<li class="header">PART TWO</li>
<li class="chapter " data-level="4.1" data-path="2-0-0-overview.html">
<a href="2-0-0-overview.html">
The Suffusion of Blue
</a>
<ul class="articles">
<li class="chapter " data-level="4.1.1" data-path="2-01-0-programming-paradigms.html">
<a href="2-01-0-programming-paradigms.html">
Programming Paradigms
</a>
</li>
<li class="chapter " data-level="4.1.2" data-path="2-02-0-regex.html">
<a href="2-02-0-regex.html">
Extra Credit: Regular Expressions
</a>
</li>
<li class="chapter " data-level="4.1.3" data-path="2-03-0-objects-control.html">
<a href="2-03-0-objects-control.html">
Objects and Control Structures
</a>
</li>
<li class="chapter " data-level="4.1.4" data-path="2-04-0-data-persistence.html">
<a href="2-04-0-data-persistence.html">
Extra Credit: Persistence and Databases
</a>
</li>
<li class="chapter " data-level="4.1.5" data-path="2-05-0-extended-types.html">
<a href="2-05-0-extended-types.html">
Extended Types
</a>
</li>
<li class="chapter " data-level="4.1.6" data-path="2-06-0-threads-memos-parallel.html">
<a href="2-06-0-threads-memos-parallel.html">
Extra Credit: Concurrency and Memoization
</a>
</li>
<li class="chapter " data-level="4.1.7" data-path="2-07-0-logic-and-more-math.html">
<a href="2-07-0-logic-and-more-math.html">
Logic and Advanced Math
</a>
</li>
<li class="chapter " data-level="4.1.8" data-path="2-08-0-number-theory.html">
<a href="2-08-0-number-theory.html">
Extra Credit: Number Theory
</a>
</li>
<li class="chapter " data-level="4.1.9" data-path="2-09-0-binary-octets-bits.html">
<a href="2-09-0-binary-octets-bits.html">
Binary Streams, Octet-Vectors, and Bit-Vectors
</a>
</li>
<li class="chapter " data-level="4.1.10" data-path="2-10-0-improved-text-adventure-engine.html">
<a href="2-10-0-improved-text-adventure-engine.html">
Extra Credit: An Improved Text Adventure Engine
</a>
</li>
<li class="chapter " data-level="4.1.11" data-path="2-11-0-conditions.html">
<a href="2-11-0-conditions.html">
Conditions and Error Handling
</a>
</li>
<li class="chapter " data-level="4.1.12" data-path="2-12-0-2d-game.html">
<a href="2-12-0-2d-game.html">
Extra Credit: Write a 2D Game
</a>
</li>
<li class="chapter " data-level="4.1.13" data-path="2-13-0-compiler.html">
<a href="2-13-0-compiler.html">
The Compiler
</a>
</li>
<li class="chapter " data-level="4.1.14" data-path="2-14-0-tree-shaker.html">
<a href="2-14-0-tree-shaker.html">
Extra Credit: Write a Tree-Shaker
</a>
</li>
<li class="chapter " data-level="4.1.15" data-path="2-15-0-docs-and-inspection.html">
<a href="2-15-0-docs-and-inspection.html">
Documentation and Inspection
</a>
</li>
<li class="chapter " data-level="4.1.16" data-path="2-16-0-foreign-libs.html">
<a href="2-16-0-foreign-libs.html">
Extra Credit: Foreign Libraries in Lisp
</a>
</li>
<li class="chapter " data-level="4.1.17" data-path="2-17-0-debugging-testing.html">
<a href="2-17-0-debugging-testing.html">
Debugging and Unit Testing
</a>
</li>
<li class="chapter " data-level="4.1.18" data-path="2-18-0-ffi.html">
<a href="2-18-0-ffi.html">
Extra Credit: Write a Foreign Function Interface
</a>
</li>
<li class="chapter " data-level="4.1.19" data-path="2-19-0-essential-libs.html">
<a href="2-19-0-essential-libs.html">
Essential Lisp Libraries
</a>
</li>
<li class="chapter " data-level="4.1.20" data-path="2-20-0-packaging-libs.html">
<a href="2-20-0-packaging-libs.html">
Extra Credit: Packaging Lisp Libraries
</a>
</li>
<li class="chapter " data-level="4.1.21" data-path="2-21-0-review.html">
<a href="2-21-0-review.html">
Detailed Syntax Review
</a>
</li>
</ul>
</li>
<li class="header">PART THREE</li>
<li class="chapter " data-level="5.1" data-path="3-00-00-overview.html">
<a href="3-00-00-overview.html">
Lisp So(u)rcery
</a>
<ul class="articles">
<li class="chapter " data-level="5.1.1" data-path="3-01-00-web-apps.html">
<a href="3-01-00-web-apps.html">
Real-world Web Apps
</a>
</li>
<li class="chapter " data-level="5.1.2" data-path="3-02-00-typesetting.html">
<a href="3-02-00-typesetting.html">
Typesetting
</a>
</li>
<li class="chapter " data-level="5.1.3" data-path="3-03-00-mobile.html">
<a href="3-03-00-mobile.html">
Native Mobile Applications
</a>
</li>
<li class="chapter " data-level="5.1.4" data-path="3-04-00-gui.html">
<a href="3-04-00-gui.html">
Cross-platform Desktop Applications
</a>
</li>
<li class="chapter " data-level="5.1.5" data-path="3-05-00-system-utils.html">
<a href="3-05-00-system-utils.html">
Drivers, Daemons, and System-Utilities
</a>
</li>
<li class="chapter " data-level="5.1.6" data-path="3-06-00-reverse-engineering.html">
<a href="3-06-00-reverse-engineering.html">
Reverse Engineering
</a>
</li>
<li class="chapter " data-level="5.1.7" data-path="3-07-00-graphics.html">
<a href="3-07-00-graphics.html">
Graphics Rendering
</a>
</li>
<li class="chapter " data-level="5.1.8" data-path="3-08-00-gaming.html">
<a href="3-08-00-gaming.html">
OpenGL, SDL, and 3D Game Development
</a>
</li>
<li class="chapter " data-level="5.1.9" data-path="3-09-00-audio.html">
<a href="3-09-00-audio.html">
Audio Generation and Manipulation
</a>
</li>
<li class="chapter " data-level="5.1.10" data-path="3-10-00-data.html">
<a href="3-10-00-data.html">
Data Aggregation and Analysis
</a>
</li>
<li class="chapter " data-level="5.1.11" data-path="3-11-00-cryptosec.html">
<a href="3-11-00-cryptosec.html">
Cryptography and Security
</a>
</li>
<li class="chapter " data-level="5.1.12" data-path="3-12-00-fintech.html">
<a href="3-12-00-fintech.html">
Financial Software and Crypto-Currencies
</a>
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<a href="index.html" >Mapping and Looping</a>
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<h1 id="chapter-116">Chapter 1.16</h1>
<h2 id="mapping-and-looping">Mapping and Looping</h2>
<blockquote>
<p>&quot;Excuse me, Doctor; I did not mean to criticize your planet.&quot;</p>
<footer>Robert A. Heinlein, <em>The Moon Is a Harsh Mistress</em></footer>
</blockquote>
<p>As a contrast to Conditionals, sometimes you&apos;ll want to do exactly the same thing to each item in a whole list or sequence; or maybe not <em>exactly</em> the same thing, but very similar things. Once again, Lisp has you covered---there are quite a few built-in options for iteration over lists, sets, sequences, hash tables, and other such objects. Basic iteration is covered by the &quot;DO&quot; series of functions.</p>
<p>Mapping is a different beast than iteration, but you may find a certain synchronicity between the two topics that help you understand both better. For example, if you have two lists, and you want to pair the values of one list with the values of the other, you can map them together using the <code>cons</code> function to get an alist as key-value pairs---and you can see here the similarity between mapping and looping.</p>
<p>Lisp also has the functions <code>apply</code> and <code>reduce</code>, of course---<code>apply</code> takes a function as its first argument, and then applies that function to the rest of the arguments you pass it, the last of which must be a list; <code>reduce</code> is somewhat similar, but it works with sequences and allows you to specify a number of extra parameters for finer control.</p>
<p>And then there&apos;s the infamous and oft-criticized <code>LOOP</code> macro---it gets a lot of flak for not being &quot;Lispy&quot; enough, but it&apos;s so powerful that it has stuck around. It has its own internal syntax that looks more like imperative languages than like Lisp, however, it includes the functionality for every possible iterative construct you could ever hope or dream for.</p>
<p>This chapter will contain exercises on:</p>
<ul>
<li><code>DO</code> and <code>DO*</code></li>
<li><code>DOTIMES</code></li>
<li><code>DOLIST</code></li>
<li><code>MAP</code></li>
<li><code>MAPC</code> and <code>MAPL</code></li>
<li>Other Mapping Functions</li>
<li><code>APPLY</code> and <code>REDUCE</code></li>
<li>The <code>LOOP</code> Macro</li>
</ul>
<h3 id="exercise-1161">Exercise 1.16.1</h3>
<p><strong>Iteration</strong></p>
<h3 id="exercise-1162">Exercise 1.16.2</h3>
<p><strong>DO</strong></p>
<h3 id="exercise-1163">Exercise 1.16.3</h3>
<p><strong>DO*</strong></p>
<h3 id="exercise-1164">Exercise 1.16.4</h3>
<p><strong>DOTIMES</strong></p>
<h3 id="exercise-1165">Exercise 1.16.5</h3>
<p><strong>DOLIST</strong></p>
<h3 id="exercise-1166">Exercise 1.16.6</h3>
<p><strong>Mapping</strong></p>
<h3 id="exercise-1167">Exercise 1.16.7</h3>
<p><strong>MAP</strong></p>
<h3 id="exercise-1168">Exercise 1.16.8</h3>
<p><strong>MAPC</strong></p>
<h3 id="exercise-1169">Exercise 1.16.9</h3>
<p><strong>MAPL</strong></p>
<h3 id="exercise-11610">Exercise 1.16.10</h3>
<p><strong>MAPCAR</strong></p>
<h3 id="exercise-11611">Exercise 1.16.11</h3>
<p><strong>MAPCAN</strong></p>
<h3 id="exercise-11612">Exercise 1.16.12</h3>
<p><strong>MAPHASH</strong></p>
<h3 id="exercise-11613">Exercise 1.16.13</h3>
<p><strong>MAPCON</strong></p>
<h3 id="exercise-11614">Exercise 1.16.14</h3>
<p><strong>MAP-INTO</strong></p>
<h3 id="exercise-11615">Exercise 1.16.15</h3>
<p><strong>APPLY</strong></p>
<h3 id="exercise-11616">Exercise 1.16.16</h3>
<p><strong>More APPLY</strong></p>
<h3 id="exercise-11617">Exercise 1.16.17</h3>
<p><strong>REDUCE</strong></p>
<h3 id="exercise-11618">Exercise 1.16.18</h3>
<p><strong>More REDUCE</strong></p>
<h3 id="exercise-11619">Exercise 1.16.19</h3>
<p><strong>The LOOP Macro</strong></p>
<h3 id="exercise-11620">Exercise 1.16.20</h3>
<p><strong>More LOOP</strong></p>
<h3 id="exercise-11621">Exercise 1.16.21</h3>
<p><strong>Even More LOOP</strong></p>
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