How do you printf and sprintf in Io?

How can I:

• convert an object to a string without printing it, a la Python's str(obj)?
• print using percent (%) directives a la C's printf(format, obj1, obj2, ...)?
• create a string using percent (%) directive开发者_运维问答s without printing to stdout a la C's sprintf(str, fmt, obj1, obj2, ...)?

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Interpolation:

"2 + 2 = #{4}" interpolate

Concatenation:

"2 + 2 = " .. 4 asString

Interpolation with printing:

"2 + 2 = #{4}" interpolate println

Concatenation with printing:

("2 + 2 = " .. 4 asString) println