integer

• 200.abs is the absolute value.
• 200.next return the next integer.
• leading sign: 0 for octal, 0x for hex, ob for binary
• underscore: underscore chars are ignored in digit

float

• 123.45.round follow the round rule
• 123.45.ceil means rounding up
• 123.54.floor means rounding down
• 123.54.to_i same as rounding down