monic part 5: writing C programs on the calculator

[F-73P]

I've created a new type specifier ("local") for local variables (which can be declared at the beginning of a function and are valid only in that function) and another type specifier for arrays ("array"). I've removed the other type specifiers from the grammar, as the first word of each object pushed onto the stack determines the object type. I've also added Boolean data types. Below is the EBNF grammar for the mC programming language (tokens are in uppercase/quotation marks):

Code:


program -> code ENDFILE

code -> { array-declaration } { function-declaration } main-function-declaration

array-declaration -> ARRAY ID dimensions SEMICOLON

dimensions -> LEFTBRACKET NUM RIGHTBRACKET { LEFTBRACKET NUM RIGHTBRACKET }

function-declaration -> ID LEFTPARENTHESIS params RIGHTPARENTHESIS LEFTBRACE local-declarations statement-list RIGHTBRACE

params -> [ param { COMMA param } ]

param -> ID { LEFTBRACKET NUM RIGHTBRACKET }

main-function-declaration -> MAIN LEFTBRACE local-declarations statement-list RIGHTBRACE

local-declarations -> { LOCAL var-declaration }

var-declaration -> ID SEMICOLON | array-declaration

statement-list -> { statement }

statement -> compound-stmt | if-stmt | while-stmt | do-stmt | for-stmt | switch-stmt | return-stmt | read-stmt | write-stmt | assignment-stmt | expression-stmt | goto-stmt | label-stmt | nop-stmt 

compound-stmt -> LEFTBRACE statement-list RIGHTBRACE

if-stmt -> IF LEFTPARENTHESIS Boolean-expression RIGHTPARENTHESIS statement [ ELSE statement ]

while-stmt -> WHILE LEFTPARENTHESIS Boolean-expression RIGHTPARENTHESIS statement

do-stmt -> DO statement WHILE LEFTPARENTHESIS Boolean-expression RIGHTPARENTHESIS SEMICOLON

for-stmt -> FOR LEFTPARENTHESIS [ assignment ] SEMICOLON Boolean-expression SEMICOLON [ addditive-expression ] RIGHTPARENTHESIS statement 

switch-stmt -> SWITCH LEFTPARENTHESIS ID { LEFTBRACKET additive-expression RIGHTBRACKET } RIGHTPARENTHESIS LEFTBRACE { CASE NUM COLON statement-list BREAK SEMICOLON } [ DEFAULT COLON statement-list ] RIGHTBRACE  

return-stmt -> RETURN [ expression ] SEMICOLON    

read-stmt -> READ ID { LEFTBRACKET additive-expression RIGHTBRACKET } SEMICOLON 

write-stmt -> WRITE expression SEMICOLON 

assignment-stmt -> assignment SEMICOLON

expression-stmt -> [ expression ] SEMICOLON

goto-stmt -> GOTO ID SEMICOLON

label-stmt -> ID COLON statement

nop-stmt -> NOPR SEMICOLON

assignment -> ID { LEFTBRACKET additive-expression RIGHTBRACKET } "=" expression 

expression -> Boolean-expression | additive-expression
 
Boolean-expression -> logical-expression { boolop logical-expression } 

logical-expression -> additive-expression relop additive-expression | ID { LEFTBRACKET additive-expression RIGHTBRACKET } | TRUE | FALSE 

additive-expression -> term { addop term }

term -> [ NEGATE ] factor { mulop [ NEGATE ] factor }

factor -> LEFTPARENTHESIS additive-expression RIGHTPARENTHESIS | NUM | ID { LEFTBRACKET additive-expression RIGHTBRACKET } | ID LEFTPARENTHESIS args RIGHTPARENTHESIS | ID "++" | ID "--" 

args -> [ expression { COMMA expression } ]

boolop -> "and" | "or" | "not"

relop -> "<=" | "<" | ">" | ">=" | "==" | "!=" 

addop -> "+" | "-"

mulop -> "*" | "/"

Some test programs:

1) factorial using a while loop

Code:


/*factorial program 1*/

main{
   read x;                          
   factorial=1;
   while (x>0) {
     factorial = factorial*x;
     x--;                          
   }
   write factorial;
}

2) factorial using recursion

Code:


/*factorial program 2*/

fact(x){
   if (x==1) return 1;
   else return x*fact(x-1);
}  

main{                          
    read y;
    if (y>1) fact(y);
    else write 1;                        
}

3) squaring a number using nested for loops

Code:


/*square program*/

main{
   read x;
   product=0;    
   for(i=x;i>=1;i--) {
      for(j=1;j<=x;j++) {
        product++;
      }
   }                          
   write product;
}