programming in ANSI C-Chapter 3 Operators and Expressions

.,Chapter3OperatorsandExpressions,PROGRAMMINGINANSIC,.,Operators,.,Expressions,Anexpressionisasequenceofoperandsandoperatorsthatproducesasinglevalue.Thisvaluemaybeanydatatypeexceptvoid.,.,Howtolearnoperatorsandexpressions?,Whenwestudyoperatorsandexpressions,wemustpayattentiontosuch5points:Thefunctionofoperators.Therelationofoperatorsandoperands:Howmanyoperandsdoestheoperatorneed?Whichtypesdoestheoperatorrequire?Theprecedenceoftheoperator.Theassociativityoftheoperator.Thetypeofthecalculatedresult.,.,ArithmeticOperatorsCdoesntsupplyexponentialoperator,soyoucanwritesomemultiplication,oryoucanusemathematicfunctionpow(x,y)intheCfunctionlibrarytoexpressxy;Noticetheprecedenceofthosearithmeticoperators,andyoushouldreasonablyuseparentheses.,.,ArithmeticOperatorsb=a*3.0;Dontmakeanyexpressiondividezero.Avoiddataoverflow.,.,RelationalOperatorsabc=ababf=abc,32，thevalueis11=1，thevalueis1b+c=3，thevalueis0d=1abis1，1cis0，so:f=0,.,RelationalOperatorsinta=b=5;Wrong!inta=5,b=5;Right!,.,AssignmentOperatorsa=b=c=5;a=5+(c=6);a=(b=4)+(c=6);,c=5,b=c,a=b/*a=5,b=5,c=5*/c=6,a=5+c/*a=11,c=6*/b=4,c=6,a=b+c/*a=10,b=4,c=6*/,.,AssignmentOperatorsisequivalentto:variable=variableopexpressione.g.x*=y+1;isequivalentto:x=x*(y+1);,.,AssignmentOperatorsa+=a-=a*a;,a+=a=4a+=(a=a4)a+=(a=-2)a+=aa=a+aa=(-2)+(-2)a=-4,.,IncrementandDecrementOperators,+-m+;or+m;isequivalentto:m=m+1;m-;or-m;isequivalentto:m=m-1;Precedence：sameasunary+,unary-,!Associativity：Righttoleft,(10/m)+Wrong!10/m+Right!,.,IncrementandDecrementOperators,intm=5,n;n=10/m+;isequivalentto:n=10/m;m+;n=10/+m;isequivalentto:+m;n=10/m;,.,IncrementandDecrementOperators,j=3;k=+j;j=3;k=j+;j=3;printf(%d,+j);j=3;printf(%d,j+);a=3;b=5;c=(+a)*b;a=3;b=5;c=(a+)*b;,j=j+1;k=j;result：k=4,j=4k=j;j=j+1;result：k=3,j=4j=j+1;printf();output:4printf();j=j+1;output:3a=a+1;c=a*b;result：a=4，c=20c=a*b;a=a+1;result：a=4，c=15,.,IncrementandDecrementOperators,NoticeTheoperandof+or-mustbeavariableandnotanyexpressionoranyconstant.,.,CommaOperatorb=(a=3*4,5*2);a=1;b=2;c=3;printf(%d,%d,%d,a,b,c);printf(%d,%d,%d,(a,b,c),b,c);,a=12a=12,b=10output:1,2,3output:3,2,3,.,ImplicitTypeConversion,Therulesofconversion:P67Inallexpressionsexceptassignments,anyimplicittypeconversionsaremadefromalowersizetypetoahighersizetypeasshownhere:,.,ImplicitTypeConversion,Duringassignment:Ifexpressionisrealtypeandthevariableisintegertype,thevalueofexpressionwillbetruncateditsfractionalpart.Ifexpressionisdoubletypeandthevariableisfloattype,thevalueofexpressionwillberounditsdigits.Ifexpressionislongtypeandthevariableisinttype,thevalueofexpressionwillbedropitshigherbyte.,.,ImplicitTypeConversion,inti,x;floatf;doubled;longL;x=L/i+i*f-d;,long,float,float,float,double,double,double,int,Notice:inthewholeprocessoftypeconversion,onlythetypeoftheinterimvalueusedinevaluationisconverted,butallthetypesofvariablesarenotconverted.Exceptthevariable“x”assignedavalue,allthevaluesofothervariablesarenotchanged.,.,ExplicitTypeConversion,Form：(type-name)expressionPrecedence：sameasunary+,unary-,!,+,-Associativity：Righttolefte.g.(int)(x+y)(int)x+y,main()floatx,y;x=3.6;y=(int)x*2;printf(x=%.2f,y=%.2f,x,y);,x=3.60,y=6.00,Notice:liketheimplicittypeconversion,onlythetypeoftheinterimvalueusedinevaluationisconverted,butallthe