Type conversion vs Type cast

• Conversion: creates new value (typically primitives)
  • Sometimes cast to unsigned int is a cast or a conversion (g++ is cast)
• Cast: Changes label, or way object is seen, data is not changed

Categories:

• Explicit vs implicit
• Widening vs narrowing
• Checked vs unchecked

Explicit vs Implicit

• Explicit: Requires you to use the actual syntax to do
• Implicit: opposite
  • Example: passing int into float param
  • Most implicit casts are upcasts

static_cast in C++ is ironically a conversion

C++ Implicit Conversion Rules

• If either operand is a long double, convert other to long double
• “ double
• “ float
• “ unsigned long int
• Operands are long int and unsigned int and long int can represent unsigned int, then convert unsigned int to long int

Implicit conversion: coercion

PL lingo: a coercion that converts a narrow type into a wider type is a type promotion. (Int→Long, etc.)

Widening vs Narrowing