Type checking for expressions

E num	E.type = int
E num.num	E.type = real
E id	E.type = lookup( id.entry
E E 1 op E 2	E.type = if E 1 .type == int && E 2 .type == int
	then int
	elseif E 1 .type == int && E 2 .type == real
	then real
	elseif E 1 .type == real && E 2 .type == int
	then real
	elseif E 1 .type == real && E 2 .type== real
	then real

The language has to perform implicit type conversions where ever it is possible. As a thumb rule compiler performs a type conversion if it doesn't lead to any loss of information. For example, int can be converted into real, single precision to a double precision etc. under this rule. Compilers also support explicit type conversions. This conversion translates into many cases in the type assignment of a Left Hand side of a expression. For example, x = y + z ; Then the type of x depends on the type of y, z as described above.