函数与子程序.ppt

函数、子程序,一个完整的较复杂一点的程序应该有,主程序函数子程序,过程（固有，外部）,内容,固有函数，函数子过程递归(recursive),固有函数,sin,cos,index,trim,用法1)write(*,*)sin(x),cos(2.0),trim(hhhh_),trim(name)2)open(1,file=trim(file_name),status=old,action=read)3)y=cos(x)*sin(1.5)4)if(sin(x)=0.0)thenendif,函数是一一映射或多对一映射返回的是单值！,外部函数,格式FUNCTION函数名(输入变量)RESULT(输出结果)函数主体ENDFUNCTION函数名,外部函数,格式FUNCTIONconvert_angle(met_angle)RESULT(mat_angle)！implicitnone!real,intent(in):met_anglereal:mat_angle!real:integer:i,j,k!ENDFUNCTIONconvert_angle,注意：1）intent(in)intent(inout)intent(in):met_angle不能met_angle=met_angle+180.不允许对intent(in)变量进行改变！,一个例子,PROGRAMtest!implicitnone!real:s,sin_cos!s=99.write(*,*)sin_cos(s)!ENDPROGRAMtestFUNCTIONsin_cos(x)RESULT(y)!implicitnone!real,intent(in):xreal:y!y=sin(x)*cos(x)!ENDFUNCTIONsin_cos,注意：函数名要作为一个变量在主程序中声明！如左边的sin_cos,一个例子,PROGRAMtest!implicitnone!real:s,sin_cos!s=99.write(*,*)swrite(*,*)sin_cos(s)write(*,*)s!ENDPROGRAMtestFUNCTIONsin_cos(x)RESULT(y)!implicitnone!real,intent(inout):xreal:y!y=sin(x)*cos(x)x=x+1.0!ENDFUNCTIONsin_cos,名词(1)哑元，实元哑实结合数据传递的一种方式(2)局部变量,不良习惯！改变输入变量，如左边的x。在函数里，不要用inout,应全部用in!防止改变输入变量,函数返回单值！(1),FUNCTIONsin_cos(x,y)RESULT(y1,y2)!implicitnone!real,intent(in):x,yreal:y1,y2!y1=sin(x)*cos(y)y2=sin(y)*cos(x)!ENDFUNCTIONsin_cos,Wrong!,函数返回单值！(2),FUNCTIONsin_cos(x,y)RESULT(xy)!implicitnone!real:x,yreal,dimension(2):xy!xy(1)=sin(y)*cos(x)xy(2)=sin(y)*cos(x)!ENDFUNCTIONsin_cos,Wrong!,可选变元,功能：调用时可改变函数内部的执行FUNCTIONadd(x1,x2,x3,if_add)RESULT(sum)!implicitnone!integer,optional,intent(in):if_addreal,intent(in):x1,x2,x3real:sum!if(present(if_add)thensum=(x1+x2)*if_addelsesum=x1+x2+x3endif!ENDFUNCTIONadd,PROGRAMtesty1=add(4.1,2.3,9.3,2)y2=add(4.1,2.3,9.3)write(*,*)y1,y2ENDPROGRAMtest,是否可以有多个可选变量？取决于编译器！目前，ifort可以！pgf90不行！,既能求出圆柱底面积，也能求出体积,现场小练习,问题：编写程序，完成功能：屏幕输入一个字符串和一个实数，格式如下：met355.0或者（气象角）mat180.0（数学角）然后进行气象角与数学角的自动转换（函数完成）。屏幕输入过程可以无限多次！,PROGRAMangle!implicitnone!character(len=10):angle_typereal:convert_angle,angle_in,angle_out!-readangle_typeandanglefromscreen!-andconvertangleaccordingtoangle_typewrite(*,*)write(*,*)Pleaseinputangle_typeandangle!write(*,*)Forexample:met355.0write(*,*)or.mat-180.2write(*,*)type999999toendprogram!write(*,*)!,angle_convert:&DOread(*,*)angle_type,angle_in!if(trim(angle_type)=999.and.angle_in=999)exitangle_convertangle_out=convert_angle(angle_type,angle_in)!if(trim(angle_type)=met)thenwrite(*,(2(a,f7.2)meteorologicalangle,angle_in,&-mathematicalangle,angle_outelseif(trim(angle_type)=mat)thenwrite(*,(2(a,f7.2)mathematicalangle,angle_in,&-meteorologicalangle,angle_outendif!ENDDOangle_convert!ENDPROGRAMangle,FUNCTIONconvert_angle(angle_type,ang1)RESULT(ang2)!implicitnone!character(len=10),intent(in):angle_typereal,intent(in):ang1real:ang2!-formula:ang1+ang2=270.if(trim(angle_type)=met.or.trim(angle_type)=mat)thenang2=270.-ang1elsewrite(*,*)angletypeisnotrecognised!callabort()endif!ENDFUNCTIONconvert_angle,子程序,固有子程序（编译器自带）日期与时间date_and_time(date,time,)system_clock(count,count_rate)cpu_time(time)随机数生成器random_number(a)random_seed(size,put,get)外部子程序（我们自己动手设计与编写）,ccyymmdd,hhmmss.sss,字符型,使用date_and_time,PROGRAMtest!implicitnone!character(len=8):todaycharacter(len=10):time!CALLdate_and_time(today,time)!write(*,(a,a)Todayis,todaywrite(*,(a)Nowitis/time(1:6)!ENDPROGRAMtest,使用cpu_time,PROGRAMtest!implicitnone!real,dimension(2):time!CALLcpu_time(time(1)!,!CALLcpu_time(time(2)!write(*,*)Timeusedis,time(2)-time(1)!ENDPROGRAMtest,子程序,SUBROUTINE子程序名称(输入变量，输出变量)!ENDSUBROUTINE子程序名称,子程序,SUBROUTINEexample(x1,x2,x3,x4,y1,y2,y3)!implicitnone!real,intent(in):x1,x2,x3,x4real,intent(out):y1,y2,y3!y1=x1y2=x2y3=x3+x4!ENDSUBROUTINEexample,PROGRAMtest.real:xx1,xx2,xx3,xx4real:yy1,yy2,yy3CALLexample(xx1,xx2,&xx3,xx4,yy1,yy2,yy3)ENDPROGRAMtest,哑元，实元哑实结合,改为子程序,CALLbubble_sort(new_list,num+1),主程序、子程序之间的关系,PROGRAMtestreal:x1,x2,x3,y1,y2,y3CALLsub1(x1,y1)CALLsub2(x2,y1,y2)CALLsub3(x3,y2,y3)ENDPROGRAMtestSUBROUTINEsub1(x1,y1)real,intent(in):x1real,intent(out):y1