📄 sxsy05_211.mht
字号:
family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>改为=
</span><span
lang=3DEN-US>Evaluate[fun[x]]</span><span style=3D'font-family:SimSun;mso-a=
scii-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>来实=
现上面的功能。</span></p>
<p class=3DMsoNormal style=3D'text-indent:21.75pt;line-height:125%;vertical=
-align:
top'><span style=3D'font-family:SimSun;mso-ascii-font-family:"Times New Rom=
an";
mso-hansi-font-family:"Times New Roman"'>例</span><span lang=3DEN-US>=
3</span><span
style=3D'font-family:SimSun;mso-ascii-font-family:"Times New Roman";mso-han=
si-font-family:
"Times New Roman"'>：定义递归函数=
。<span
class=3DGramE>非波那</span>奇数列਷=
9;我们熟悉的数列，我&=
#20204;可以通过下面的</span><span
class=3DSpellE><span lang=3DEN-US>Mathematica</span></span><span style=3D'f=
ont-family:
SimSun;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times=
New Roman"'>程序来生成该数࠵=
5;：</span><span
lang=3DEN-US>f[1]=3D1;f[2]=3D1;f[x_]:=3Df[x-1]+f[x-2]</span></p>
<p class=3DMsoNormal style=3D'text-indent:21.75pt;line-height:125%;vertical=
-align:
top'><span style=3D'font-family:SimSun;mso-ascii-font-family:"Times New Rom=
an";
mso-hansi-font-family:"Times New Roman"'>也可以用</=
span><span
lang=3DEN-US>f[1]=3D1;f[2]=3D1;f[x_]:f[x]=3Df[x-1]+f[x-2]</span><span style=
=3D'font-family:
SimSun;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times=
New Roman"'>来定义，当我们ஷ=
2;后者时，只要我们一&=
#26086;计算了</span><span
lang=3DEN-US>f[n]</span><span style=3D'font-family:SimSun;mso-ascii-font-fa=
mily:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>则所=
有小于</span><span
lang=3DEN-US>n</span><span style=3D'font-family:SimSun;mso-ascii-font-famil=
y:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>的整数</span><sp=
an
class=3DSpellE><span lang=3DEN-US>i</span></span><span style=3D'font-family=
:SimSun;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Ro=
man"'>，</span><span
lang=3DEN-US>f[<span class=3DSpellE>i</span>]</span><span style=3D'font-fam=
ily:SimSun;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Ro=
man"'>均已保留在系统中ʌ=
92;而不需要重新计算。=
</span></p>
<p class=3DMsoNormal style=3D'text-indent:21.75pt;line-height:125%;vertical=
-align:
top'><span style=3D'font-family:SimSun;mso-ascii-font-family:"Times New Rom=
an";
mso-hansi-font-family:"Times New Roman"'>我们可以&#=
20808;计算</span><span
lang=3DEN-US>f[10]</span><span style=3D'font-family:SimSun;mso-ascii-font-f=
amily:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>，再=
用</span><span
lang=3DEN-US>?f</span><span style=3D'font-family:SimSun;mso-ascii-font-fami=
ly:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>查看内存&#=
30340;情况。</span></p>
<p class=3DMsoNormal style=3D'text-indent:27.0pt;line-height:125%;vertical-=
align:
top'><b style=3D'mso-bidi-font-weight:normal'><span style=3D'font-family:Si=
mSun;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Ro=
man"'>（二）过程</span><span
lang=3DEN-US><o:p></o:p></span></b></p>
<p class=3DMsoNormal style=3D'text-indent:21.0pt;mso-char-indent-count:2.0;
line-height:125%;vertical-align:top'><span class=3DSpellE><span lang=3DEN-U=
S>Mathematica</span></span><span
style=3D'font-family:SimSun;mso-ascii-font-family:"Times New Roman";mso-han=
si-font-family:
"Times New Roman"'>中的一个过程就=
是用分号隔开的表达=
4335;序列，一个表达式ॴ=
7;列也称为一个复合表&=
#36798;式，在</span><span
class=3DSpellE><span lang=3DEN-US>Mathematica</span></span><span style=3D'f=
ont-family:
SimSun;mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times=
New Roman"'>的各种结构中，ߥ=
9;何一个表达式的位置&=
#37117;能放一个符合表达=
335;。</span></p>
<p class=3DMsoNormal style=3D'text-indent:27.0pt;line-height:125%;vertical-=
align:
top'><b style=3D'mso-bidi-font-weight:normal'><span style=3D'font-family:Si=
mSun;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Ro=
man"'>（三）条件控制语Ö=
77;</span><span
lang=3DEN-US><o:p></o:p></span></b></p>
<p class=3DMsoNormal style=3D'text-indent:21.0pt;mso-char-indent-count:2.0;
line-height:125%;vertical-align:top'><span class=3DSpellE><span lang=3DEN-U=
S>Mathematica</span></span><span
style=3D'font-family:SimSun;mso-ascii-font-family:"Times New Roman";mso-han=
si-font-family:
"Times New Roman"'>中提供了</span><span lang=3DEN-U=
S>If</span><span
style=3D'font-family:SimSun;mso-ascii-font-family:"Times New Roman";mso-han=
si-font-family:
"Times New Roman"'>、</span><span lang=3DEN-US>Which</span><span
style=3D'font-family:SimSun;mso-ascii-font-family:"Times New Roman";mso-han=
si-font-family:
"Times New Roman"'>和</span><span lang=3DEN-US>Switch</span><span
style=3D'font-family:SimSun;mso-ascii-font-family:"Times New Roman";mso-han=
si-font-family:
"Times New Roman"'>三种描述条件分=
支的结构语句，这些=
6465;件语句常用在程序ߑ=
3;。</span></p>
<p class=3DMsoNormal style=3D'text-indent:21.0pt;line-height:125%;vertical-=
align:
top'><span lang=3DEN-US>1</span><span style=3D'font-family:SimSun;mso-ascii=
-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>．</span><=
span
lang=3DEN-US>If</span><span style=3D'font-family:SimSun;mso-ascii-font-fami=
ly:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>语句结构</=
span></p>
<p class=3DMsoNormal style=3D'margin-left:21.75pt;line-height:125%;vertical=
-align:
top'><span lang=3DEN-US>If</span><span style=3D'font-family:SimSun;mso-asci=
i-font-family:
"Times New Roman";mso-hansi-font-family:"Times New Roman"'>结构=
有下列三种情况：</span></p>
<p class=3DMsoNormal style=3D'text-indent:21.0pt;mso-char-indent-count:2.0;
line-height:125%;vertical-align:top'><span lang=3DEN-US>If[</span><span
style=3D'font-family:SimSun;mso-ascii-font-family:"Times New Roman";mso-han=
si-font-family:
"Times New Roman"'>逻辑表达式，表=
达式</span><span
lang=3DEN-US>1]</span><span style=3D'font-family:SimSun;mso-ascii-font-fami=
ly:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>：当逻辑&#=
34920;达式成立时，计算ŝ=
20;达式</span><span
lang=3DEN-US>1</span><span style=3D'font-family:SimSun;mso-ascii-font-famil=
y:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>，其值就&#=
26159;</span><span
lang=3DEN-US>If</span><span style=3D'font-family:SimSun;mso-ascii-font-fami=
ly:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>结构的值&#=
12290;</span></p>
<p class=3DMsoNormal style=3D'text-indent:21.0pt;mso-char-indent-count:2.0;
line-height:125%;vertical-align:top'><span lang=3DEN-US>If[</span><span
style=3D'font-family:SimSun;mso-ascii-font-family:"Times New Roman";mso-han=
si-font-family:
"Times New Roman"'>逻辑表达式，表=
达式</span><span
lang=3DEN-US>1</span><span style=3D'font-family:SimSun;mso-ascii-font-famil=
y:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>，表达式</=
span><span
lang=3DEN-US>2]</span><span style=3D'font-family:SimSun;mso-ascii-font-fami=
ly:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>：当逻辑&#=
34920;达式成立时，计算ŝ=
20;达式</span><span
lang=3DEN-US>1</span><span style=3D'font-family:SimSun;mso-ascii-font-famil=
y:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>，其值作&#=
20026;</span><span
lang=3DEN-US>If</span><span style=3D'font-family:SimSun;mso-ascii-font-fami=
ly:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>结构的值&#=
65307;当逻辑表达式不成ĺ=
35;时，计算表达式</span><span
lang=3DEN-US>2</span><span style=3D'font-family:SimSun;mso-ascii-font-famil=
y:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>，其值作&#=
20026;</span><span
lang=3DEN-US>If</span><span style=3D'font-family:SimSun;mso-ascii-font-fami=
ly:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>结构的值&#=
12290;</span></p>
<p class=3DMsoNormal style=3D'text-indent:21.0pt;mso-char-indent-count:2.0;
line-height:125%;vertical-align:top'><span lang=3DEN-US>If[</span><span
style=3D'font-family:SimSun;mso-ascii-font-family:"Times New Roman";mso-han=
si-font-family:
"Times New Roman"'>逻辑表达式，表=
达式</span><span
lang=3DEN-US>1</span><span style=3D'font-family:SimSun;mso-ascii-font-famil=
y:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>，表达式</=
span><span
lang=3DEN-US>2</span><span style=3D'font-family:SimSun;mso-ascii-font-famil=
y:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>，表达式</=
span><span
lang=3DEN-US>3]</span><span style=3D'font-family:SimSun;mso-ascii-font-fami=
ly:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>：当逻辑&#=
34920;达式成立时，计算ŝ=
20;达式</span><span
lang=3DEN-US>1</span><span style=3D'font-family:SimSun;mso-ascii-font-famil=
y:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>，其值作&#=
20026;</span><span
lang=3DEN-US>If</span><span style=3D'font-family:SimSun;mso-ascii-font-fami=
ly:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>结构的值&#=
65307;当逻辑表达式不成ĺ=
35;时，计算表达式</span><span
lang=3DEN-US>2</span><span style=3D'font-family:SimSun;mso-ascii-font-famil=
y:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>，其值作&#=
20026;</span><span
lang=3DEN-US>If</span><span style=3D'font-family:SimSun;mso-ascii-font-fami=
ly:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>结构的值&#=
65307;当逻辑表达式既<span
class=3DGramE>非成立</span>也非不ৎ=
4;立时（多数为无法判&=
#26029;时），计算表达式</sp=
an><span
lang=3DEN-US>3</span><span style=3D'font-family:SimSun;mso-ascii-font-famil=
y:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>，并将其&#=
20540;作为</span><span
lang=3DEN-US>If</span><span style=3D'font-family:SimSun;mso-ascii-font-fami=
ly:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>结构的值&#=
12290;</span></p>
<p class=3DMsoNormal style=3D'text-indent:21.0pt;line-height:125%;vertical-=
align:
top'><span style=3D'font-family:SimSun;mso-ascii-font-family:"Times New Rom=
an";
mso-hansi-font-family:"Times New Roman"'>例４：（</=
span><span
lang=3DEN-US>1</span><span style=3D'font-family:SimSun;mso-ascii-font-famil=
y:"Times New Roman";
mso-hansi-font-family:"Times New Roman"'>）</span><span lang=3DEN-US>=
x=3D1;If
[x>0<span class=3DGramE>,x</span>]</span></p>
<p class=3DMsoNormal style=3D'text-indent:48.0pt;line-height:125%;vertical-=
align:
top'><span style=3D'font-family:SimSun;mso-ascii-font-family:"Times New Rom=
an";
mso-hansi-font-family:"Times New Roman"'>（</span><span lang=3DEN-US>=
2</span><span
style=3D'font-family:SimSun;mso-ascii-font-family:"Times New Roman";mso-han=
si-font-family:
"Times New Roman"'>）定义</span><span lang=3DEN-US>f [x_ ,
y_]:=3DIf [x>0&&y>0, <span class=3DSpellE>x+y</span>, x-y]</s=
pan></p>
<p class=3DMsoNormal style=3D'text-indent:27.0pt;line-height:125%;vertical-=
align:
top'><span lang=3DEN-US><span style=3D'mso-spacerun:yes'> =
</span></span><span
style=3D'font-family:SimSun;mso-ascii-font-family:"Times New Roman";mso-han=
si-font-family:
"Times New Roman"'>　　</span> <span style=3D'font-family:SimSu=
n;
mso-ascii-font-family:"Times New Roman";mso-hansi-font-family:"Times New Ro=
man"'>输入</span><span
lang=3DEN-US>f [3,3]</span><span style=3D'font-family:SimSun;mso-ascii-font=
-family:
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