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diff --git a/js/games/nluqo.github.io/~bh/ssch3/part2.html b/js/games/nluqo.github.io/~bh/ssch3/part2.html new file mode 100644 index 0000000..519a345 --- /dev/null +++ b/js/games/nluqo.github.io/~bh/ssch3/part2.html @@ -0,0 +1,85 @@ +<P> + +<P> +<HTML> +<HEAD> +<TITLE>Simply Scheme: Introducing Computer Science, Part 3: Composition of Functions</TITLE> +</HEAD> +<BODY> +<CITE>Simply Scheme:</CITE> +<CITE>Introducing Computer Science</CITE> 2/e Copyright (C) 1999 MIT +<H2>Part II</H2> +<H1>Composition of Functions</H1> + +<TABLE width="100%"><TR><TD> +<IMG SRC="../simply.jpg" ALT="cover photo"> +<TD><TABLE> +<TR><TD align="right"><CITE><A HREF="http://www.cs.berkeley.edu/~bh/">Brian +Harvey</A><BR>University of California, Berkeley</CITE> +<TR><TD align="right"><CITE><A HREF="http://ccrma.stanford.edu/~matt">Matthew +Wright</A><BR>University of California, Santa Barbara</CITE> +<TR><TD align="right"><BR> +<TR><TD align="right"><A HREF="../pdf/ssch03.pdf">Download PDF version</A> +<TR><TD align="right"><A HREF="../ss-toc2.html">Back to Table of Contents</A> +<TR><TD align="right"><A HREF="../ssch2/functions.html"><STRONG>BACK</STRONG></A> +chapter thread <A HREF="people.html"><STRONG>NEXT</STRONG></A> +<TR><TD align="right"><A HREF="http://mitpress.mit.edu/0262082810">MIT +Press web page for <CITE>Simply Scheme</CITE></A> +</TABLE></TABLE> + +<HR><BIG> +<A NAME="g1"></A> +<A NAME="g2"></A> + +<P>The big idea in this part of the book is deceptively simple. It's that we +can take the value returned by one function and use it as an argument to +another function. By “hooking up” two functions in this way, we invent a +new, third function. For example, let's say we have a function that adds +the letter <CODE>s</CODE> to the end of a word: + +<P><P><CENTER><EM>add-s</EM>(“<CODE>run</CODE>”) = “<CODE>runs</CODE>”</CENTER> +<P> +and another function that puts two words together into a sentence: + +<P><P><CENTER><EM>sentence</EM>(“<CODE>day</CODE>”, “<CODE>tripper</CODE>”) = “<CODE>day tripper</CODE>”</CENTER> +<P> +We can combine these to create a new function that represents the +third person singular form of a verb: + +<P><P><CENTER><EM>third-person</EM>(verb) = <EM>sentence</EM>(“<CODE>she</CODE>”, <EM>add-s</EM>(verb))</CENTER> +<P> +That general formula looks like this when applied to a particular +verb: + +<P><P><CENTER><EM>third-person</EM>(“<CODE>sing</CODE>”) = “<CODE>she sings</CODE>”</CENTER> +<P> +The way we say it in Scheme is + +<P><PRE>(define (third-person verb) + (sentence 'she (add-s verb))) +</PRE> + +<P>(When we give an example like this at the beginning of a part, +don't worry about the fact that you don't recognize the notation. The +example is meant as a preview of what you'll learn in the coming chapters.) + +We know that this idea probably doesn't look like much of a big deal to +you. It seems obvious. Nevertheless, it will turn out that we can express +a wide variety of computational algorithms by linking functions together in +this way. This linking is what we mean by +“<A NAME="g3"></A><A NAME="g4"></A>functional programming.” + +<P> +</BIG> +<HR> +<P><A HREF="../ss-toc2.html">(back to Table of Contents)</A><P> +<A HREF="../ssch2/functions.html"><STRONG>BACK</STRONG></A> +chapter thread <A HREF="people.html"><STRONG>NEXT</STRONG></A> + +<P> +<ADDRESS> +<A HREF="../index.html">Brian Harvey</A>, +<CODE>bh@cs.berkeley.edu</CODE> +</ADDRESS> +</BODY> +</HTML> |