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wtd

Sun Oct 31, 2004 10:02 pm


Understanding Statements and Expressions

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Two of the most frequently confused terms in programming are statement and expression.

A statement in a program is code which doesn't have any value on its own.  In Turing, consider:

var hw : string := "Hello world"

This does something, but it can't be used as a value.

An expression has a value of its own.  In an ideal world it wouldn't actually do anything to the rest of the world, but very few languages enforce that.  Consider:

var hw : string := "Hello " + "world"

All together this isn't an expression, but rather a statement.  However:

"Hello " + "world"

Is an expression.  It doesn't modify either "Hello " or "world", but it creates something new and returns it.