TinyC

A considerably stripped down version of C and it is meant as a pedagogical tool for learning about compilers.

Source

The integer global variables "a" to "z" are predefined and initialized to zero, and it is not possible to declare new variables. The compiler reads the program from standard input and prints out the value of the variables that are not zero.

Examples

<program> ::= <statement>
<statement> ::= "if" <paren_expr> <statement> |
                "if" <paren_expr> <statement> "else" <statement> |
                "while" <paren_expr> <statement> |
                "do" <statement> "while" <paren_expr> ";" |
                "{" { <statement> } "}" |
                <expr> ";" |
                ";"
<paren_expr> ::= "(" <expr> ")"
<expr> ::= <test> | <id> "=" <expr>
<test> ::= <sum> | <sum> "<" <sum>
<sum> ::= <term> | <sum> "+" <term> | <sum> "-" <term>
<term> ::= <id> | <int> | <paren_expr>
<id> ::= "a" | "b" | "c" | "d" | ... | "z"
<int> ::= <an_unsigned_decimal_integer>

A few invocations of the compiler:

% echo "a=b=c=2<3;" | ./a.out
a = 1
b = 1
c = 1
% echo "{ i=1; while (i<100) i=i+i; }" | ./a.out
i = 128
% echo "{ i=125; j=100; while (i-j) if (i<j) j=j-i; else i=i-j; }" | ./a.out
i = 25
j = 25
% echo "{ i=1; do i=i+10; while (i<50); }" | ./a.out
i = 51
% echo "{ i=1; while ((i=i+10)<50) ; }" | ./a.out
i = 51
% echo "{ i=7; if (i<5) x=1; if (i<10) y=2; }" | ./a.out
i = 7
y = 2

Tags: language   native  

Last modified 07 June 2021