//<因子> ::= <标识符>|<无符号整数>|'('<表达式>')'
public void factor(List <symlist> followlst)
{
Pcode pc = compiler.pc;
List <symlist> nextlst = new List <symlist>();
symbol_table st = compiler.st;
lexical_analysis la = compiler.la;
Error er = compiler.error;
int index;
nextlst.AddRange(factorSymSet);
check(nextlst, followlst, 24);
while (factorSymSet.Contains(sym))
{
if (sym == symlist.iden)
{
index = st.position(la.word);
if (index == -1)
{
er.adderror(11);
}
else
{
record re = st.stable[index];
string kind = re.kind;
if (kind == "constant")
{
pc.gen("LIT", 0, re.val);
}
else if (kind == "variable")
{
int l = level - re.level;
int a = re.adr;
pc.gen("LOD", l, a);
}
else
{
er.adderror(21);
}
}
getsym();
}
else if (sym == symlist.number)
{
pc.gen("LIT", 0, la.num);
getsym();
}
else if (sym == symlist.LParenthesis)
{
getsym();
followlst.Add(symlist.RParenthesis);
expression(followlst);
if (sym == symlist.RParenthesis)
{
getsym();
}
else
{
er.adderror(22);
} //error
}
check(followlst, factorSymSet, 23);
}
}
//<语句> ::= <赋值语句>|<条件语句>|<当型循环语句>|<过程调用语句>|<读语句>|<写语句>|<复合语句>|<重复语句>|<空>
public void statement(List <symlist> followlst)
{
Error er = compiler.error;
symbol_table st = compiler.st;
lexical_analysis la = compiler.la;
Pcode pc = compiler.pc;
List <symlist> nextlst = new List <symlist>();
List <symlist> n2 = new List <symlist>();
int index, cx1, cx2;
switch (sym)
{
//<赋值语句> ::= <标识符>:=<表达式>
case symlist.iden:
index = st.position(la.word);
if (index == -1) //未声明
{
er.adderror(11);
}
else if (st.stable[index].kind != "variable")
{
er.adderror(12);
index = -1;
}
getsym();
if (sym == symlist.becomes)
{
getsym();
}
else //不是:=
{
er.adderror(13);
}
expression(followlst);
if (index != -1) //生成pcode
{
int l = level - st.stable[index].level;
int a = st.stable[index].adr;
pc.gen("STO", l, a);
}
break;
//<过程调用语句>::=call<标识符>
case symlist.callsym:
getsym();
if (sym == symlist.iden)
{
index = st.position(la.word);
if (index == -1)
{
er.adderror(11);
}
else if (st.stable[index].kind != "procedure")
{
index = -1;
er.adderror(15);
}
else //生成pcode
{
int l = level - st.stable[index].level;
int a = st.stable[index].adr;
pc.gen("CAL", l, a);
}
getsym();
}
else
{
er.adderror(14);
}
break;
//<复合语句> ::= begin<语句>{;<语句>}end
case symlist.beginsym:
getsym();
nextlst.Clear();
nextlst.AddRange(followlst);
n2.Clear();
n2.AddRange(stateSymSet);
n2.Add(symlist.semicolon);
statement(nextlst);
while (n2.Contains(sym))
{
if (sym == symlist.semicolon)
{
getsym();
}
else
{
er.adderror(10);
}
statement(nextlst);
}
if (sym == symlist.endsym)
{
getsym();
}
else //少了end
{
er.adderror(17);
}
break;
//<条件语句> ::= if<条件>then<语句>[else<语句>]
case symlist.ifsym:
getsym();
nextlst.Clear();
nextlst.AddRange(followlst);
nextlst.Add(symlist.thensym);
nextlst.Add(symlist.dosym);
ifstatement(nextlst);
if (sym == symlist.thensym)
{
getsym();
}
else
{
er.adderror(16);
}
cx1 = pc.cx;
pc.gen("JPC", 0, 0);
nextlst.Clear();
nextlst.AddRange(followlst);
nextlst.Add(symlist.elsesym);
statement(nextlst);
if (sym == symlist.elsesym)
{
getsym();
cx2 = pc.cx;
pc.gen("JMP", 0, 0);
statement(followlst);
pc.pcdeolst[cx1].a = cx2 + 1;
pc.pcdeolst[cx2].a = pc.cx;
}
else
{
pc.pcdeolst[cx1].a = pc.cx;
}
break;
// <当型循环语句 > ::= while< 条件 >do< 语句 >
case symlist.whilesym:
cx1 = pc.cx;
getsym();
nextlst.Clear();
nextlst.AddRange(followlst);
nextlst.Add(symlist.dosym);
ifstatement(nextlst);
cx2 = pc.cx;
pc.gen("JPC", 0, 0);
if (sym == symlist.dosym)
{
getsym();
}
else
{
er.adderror(18); //error
}
statement(followlst);
pc.gen("JMP", 0, cx1);
pc.pcdeolst[cx2].a = pc.cx;
break;
//<读语句> ::= read'('<标识符>{,<标识符>}')'
case symlist.readsym:
getsym();
if (sym == symlist.LParenthesis)
{
do
{
getsym();
if (sym == symlist.iden)
{
index = st.position(la.word);
}
else
{
index = -1;
er.adderror(32); //error
}
if (index > 0 && st.stable[index].kind != "variable")
{
getsym();
er.adderror(32);
}
else if (sym == symlist.RParenthesis || sym == symlist.semicolon)
{
er.adderror(35);
getsym();
}
else
{
int l = level - st.stable[index].level;
int a = st.stable[index].adr;
pc.gen("RED", l, a);
getsym();
}
} while (sym == symlist.comma);
}
else
{
er.adderror(33);
} //error
if (sym == symlist.RParenthesis)
{
getsym();
}
else
{
er.adderror(34);
while (!followlst.Contains(sym))
{
getsym();
}
}
break;
//<写语句> ::= write'('<标识符>{,<标识符>}')'
case symlist.writesym:
getsym();
nextlst.Clear();
nextlst.AddRange(followlst);
nextlst.Add(symlist.RParenthesis);
nextlst.Add(symlist.comma);
if (sym == symlist.LParenthesis)
{
do
{
getsym();
expression(nextlst);
pc.gen("WRT", 0, 0);
} while (sym == symlist.comma);
if (sym == symlist.RParenthesis)
{
getsym();
}
else
{
er.adderror(34);
} //error
}
else
{
er.adderror(33);
} //error
break;
//<重复语句> ::= repeat<语句>{;<语句>}until<条件>
case symlist.repeatsym:
getsym();
nextlst.Clear();
nextlst.AddRange(followlst);
nextlst.Add(symlist.untilsym);
cx1 = pc.cx;
statement(nextlst);
n2.Clear();
n2.AddRange(stateSymSet);
n2.Add(symlist.semicolon);
while (n2.Contains(sym))
{
if (sym == symlist.semicolon)
{
getsym();
}
else
{
er.adderror(10);
} //error}
statement(nextlst);
}
if (sym == symlist.untilsym)
{
getsym();
ifstatement(followlst);
pc.gen("JPC", 0, cx1);
}
else
{
er.adderror(25);
} //error
break;
}
check(followlst, new List <symlist>(), 19);
}