附录 APL/0 编译程序文本
program pl0(fa,fa1,fa2);
(*PL0 compiler with code generation*)
label 99;
const norw=13;(*of reserved words*)
txmax=100;(*length of identi%er table*)
nmax=14;(*max number of digits in numbers*)
al=10;(*length of identi%ers*)
amax=2047;(*maximum address*)
levmax=3;(*max depth of block nesting*)
cxmax=200;(*size of code array*)
type symbol=(nul,ident,number,plus,minus,times,slash,oddsym,
eql,neq,lss,leq,gtr,geq,lparen,rparen,comma,
semicolon,period,becomes,beginsym,endsym,ifsym,
thensym,whilesym,writesym,readsym,dosym,callsym,
constsym,varsym,procsym);
alfa= packed array［1..al］ of char;
object = (constant,variable,procedur);
(*wirth used the word "procedure" there,which won't work!*)
symset = set of symbol;
fct = ( lit, opr,lod,sto, cal, int, jmp, jpc);
instruction = packed record
f:fct;(*function code*)
l:0..levmax;(*level*)
a:0..amax;(*displacement addr*)
end;
(*lit 0,a load constant a
opr 0,a execute opr a
lod l,a load variable l,a
sto l,a store variable l,a
cal l,a call procedure a at level l
int 0,a increment t-register by a
jmp 0,a jump to a
jpc 0,a jump conditional to a *)
var fa:text;
fa1,fa2:text;
listswitch:boolean;(*true set list object code*)
ch:char;(*last char read*)
sym:symbol;(*last symbol read*)
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