Type conversion within assignments

E E₁ + E₂

E.place= newtmp;

if E₁ .type = integer and E₂ .type = integer

then emit(E.place ':=' E ₁ .place 'int+' E ₂ .place);

E.type = integer;

.

similar code if both E₁ .type and E₂ .type are real

.

else if E ₁ .type = int and E₂ .type = real

then

u = newtmp;

emit(u ':=' inttoreal E ₁ .place);

emit(E.place ':=' u 'real+' E₂ .place);

E.type = real;

.

similar code if E₁ .type is real and E₂ .type is integer

When a compiler encounters mixed type operations it either rejects certain mixed type operations or generates coercion instructions for them.

Semantic action for E -> E1+ E2:

E.place= newtmp;

if E1.type = integer and E2.type = integer

then emit(E.place ':=' E1.place 'int+' E2.place);

E.type = integer;

..

similar code if both E1.type and E2.type are real

.

else if E1.type = int and E2.type = real

then

u = newtmp;

emit(u ':=' inttoreal E1.place);

emit(E.place ':=' u 'real+' E2.place);

E.type = real;

.

similar code if E1.type is real and E2.type is integer

The three address statement of the form u ':=' inttoreal E1.place denotes conversion of an integer to real. int+ denotes integer addition and real+ denotes real addition.

Code generation is done along with type checking and if type resolution can be done in a single pass no intermediate representation like an abstract syntax tree would be required.